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MG Midget and Sprite Technical - Piston diagnosis
| Finally I have got round to making a start on my 1275 refresh prompted by an increase in general blue smoke which is most prominent under steady acceleration, not on overrun. The engine was fully rebuilt with lightened and balanced crank/flywheel/harmonic balancer. Mains and big ends were ground -10 and the cylinders bored +30 with new pistons and rings fitted. Head is an MG Metro, skimmed to give just over 10:1 compression and it is fed by a HIF44 via a Titan manifold. All that was about 80,000 miles ago. Other than the oil burning it was still running well with compression of 195/190/190/180 (dry) and 205/200/200/195 (wet) I am not wanting to do a full re-build, but to freshen it up for perhaps another 30,000 As compression is good, the plan for the head is to just lap the valves and fit new valve stem seals. As the ratio is already high I don't really want to skim the head - I think it is OK. The bottom end however needs attention. I have dropped the sump and removed the pistons. The big end shells don't have any significant scratches - they are even grey, but the top halves are just beginning to show slight signs of the copper backing showing through. I will polish the crank pins and fit new shells. I haven't checked the mains yet. Now the pistons: They show quite a lot of blow-by down the sides in line with the block axis. The thrust and return sides are clean by comparison. The bores are shiny with some slight vertical scratches visible, but not enough to catch a finger nail. There doesn't seem to be a wear ridge a the top of the bores. I am thinking to hone the bores to break the glaze and to fit new rings. But what do friends think? Photos of the piston to follow.  |
| Guy W |
Another photo
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| Guy W |
and the crown:
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| Guy W |
| Guy. I think you have taken good care of your engine over the years. The pistons look in better condition than most that I have seen. I would not expect to see a ridge at the top of the cylinder bores with modern oils that have been used for the last forty years. I removed the pistons from an engine with a documented 98K miles and found no ridge and could still see some of the honing marks from the factory build. I would measure the cylinders, front to rear and side to side, and, if they are within limits, install a new set of rings on the pistons and drive it. Hone as necessary before installing the pistons, but it may not be needed. Les |
| Les Bengtson |
| Thanks Les, I have always used standard 20/50 and changed it and the filter every 6000 miles. I always warm the engine for the first few miles, but thereafter do drive it pretty hard. I don't have a bore gauge. I seem to recall the same can be achieved using a ring at top and bottom of the bore and measuring the gap with a feeler gauge. Anyone know about that? |
| Guy W |
| Guy that won't measure ovality, which is what usually happens to the bores. You need to measure two diameters at 90 degrees to each other. |
| David Smith |
| Ah, got it. That would measure taper wouldn't it. Guess I will have to find an internal bore mic. of some sort. |
| Guy W |
| Ring it Guy. I've just ringed my 120K plus engine, it's going a storm, and not smoking at all-- AND, I reused the oil control rings -- see below. But in a previous discussion, I seem to remember you were having trouble identifying the Pistons. You should get the comp rings easy enough, but may struggle with the oil control ring (width). That's why I reused my oil control rings. I've got hepolite 19320 pistons. Got a ring set, perfect for the comp rings, but the oil controls were too wide. If not going cords, contact Thorntons. They seem to be able to match pretty much any pistons/rings. http://www.fwthornton.co.uk/index.html |
| Lawrence Slater |
| No Lawrence, I know the exact piston make, size and grade. Its just that they are not OE and the spec doesn't give data on the rings themselves. - Thanks for that link - I'm off to look at it now! David, are these devices any good for measuring the bores? Are they sufficiently accurate when in effect double measuring? http://tinyurl.com/hngmty9 |
| Guy W |
| What puzzles me is the positioning of the apparent blow-by, along the axis of the engine. I would have expected bore and ring wear wear to be greatest on the thrust side of the piston, where the piston is being pushed down hard against the cylinder side on the power stroke. I would expect any ovality to develop with a long axis across across the width of the bore and result in blow-by on those sides. Hmm, maybe as the rings wear and press further outwards across the width of the bore, it takes the ring pressure off the other axis, allowing the blow-by to occur there?? |
| Guy W |
| Guy, If you had a new ring and placed it into the bore it could only expand to the smallest bore size - thereby allowing you to check wear at the larger (trust ?) area with a feeler. Top and bottom - ring gap will show overall diameter wear. I think this is what you were referring to. A bore gauge is better, can you make a simple 'go' - 'no go' gauge. R. |
| richard boobier |
| Probably the best thing to use is a bore comparator, but they are a bit pricey. http://www.ebay.co.uk/itm/391363501867 You could maybe hire or borrow one. |
| Dave O'Neill 2 |
| Ah yes Guy. I remember now. You had a complete spare piston didn't you? Just measure the rings, width and depth. The give Thorntons a call. Pretty sure they'll be able to match them for you. But actually, unless it's an 'off the shelf' ring set, it may actually be cheaper to buy 4 new pistons. However, being +30, you'll have the same issue I had. Nobody makes +30 pistons anymore. Hence I re-ringed mine and reused the oil controls. As you only want 30k more miles from the engine, I'd re-ring it, and reuse the oil controls esp' since you have 3 comp' rings you have above them. I've only got 2, and a bit piston slap. But mine's fine, and I expect to get at least 60K more miles before it smokes and dies. On your gudgeon side blow by, read this, it may give you some clues. "Piston Scuffing If overheating is involved, the scuffing will be primarily on the upper ring lands and on the sides near the wrist pins. There may also be oil carbon and lacquer burned onto the underside of the piston indicating it was unusually hot. " http://www.enginebuildermag.com/2001/08/back-to-basics-preventing-piston-problems/ |
| Lawrence Slater |
| Cannot afford one of those for a one-off job Dave! I will try Richard's suggestion as I do have a couple of spare unused rings from the same piston set. But I am not confident of accurately measuring the ovality with a feeler gauge between the ring and the bore. Trying to slip a flat feeler gauge between two curved surfaces doesn't seem very practical. Would one of these be any good? http://tinyurl.com/hkm9p7h At least I can forsee other uses I could make of it in the future  |
| Guy W |
| You posted as I did Guy. See mine below yours. |
| Lawrence Slater |
| No evidence of piston scuffing on the sides near the wrist pins. Quite the reverse if you look at the photos Lawrence - from he blow-by there would appear to be too much clearance there! I will shoot off an enquiry to Thorntons when I have sorted out exactly what I am asking for. One thing I am not at all sure f with this is what sort of level of accuracy measurements need to be to? I am reasonably capable of getting consistent readings down to +/- 0.001" with an external mic, but if a bore has worn oval, by how much might this be and what would be considered "within tolerance" for a 60 year old design of a road engine |
| Guy W |
| Correction. I've just remembered. It wasn't the width of my oil control rings, it was the DEPTH. I couldn't compress the rails into the bores. I used a GRANTS ring set. About 35 quid. All you need to know is the dimensions of your rings. Here's a gratuitous shot of mine, cleaned up and ready for rings.  |
| Lawrence Slater |
| Yes, thanks Lawrence. Two Ronnies https://www.youtube.com/watch?v=d6Si7_e-934 I am always confused by your "see mine below yours" As your thread trail seems to be upside-down. My screen always shows the most recent message at the end of the discussion. |
| Guy W |
| Guy, if you only want 30k miles more, I'm guessing you don't want to spend a lot on the engine. I wouldn't even bother to measure the ovality of the bores, or worry about and wear on the pistons. Hence, work on the assumption that as there is little or no visible evidence of scuffing or wear in the bores or on the pistons, then perhaps there was too much clearance to begin with, and now that the rings have worn, you're smoking. +30 was an intermediate bore size, usually done to remove wear. Maybe, like mine, it really needed to go to +40 and a fatter piston to suit. But who cares? A new ring set will stop the smoking, and easily last for the 30K miles you want. If you want the full 100K miles again, rebore to +40 or more, and buy new pistons. PS. I use the "invert" option on the thread view. |
| Lawrence Slater |
| Also Guy, give Cords a call. When I spoke with them last year, they told me that if I gave them the ring dimensions, they could put together a ring set for me. I recall it was about 90 quid. Then I looked in the Grant's rings catalogue, and found a ring set for circa 35 quid, but I later discovered that the oil controls were too deep, and re-used the existing ones. You makes yer choice, and pays yer money. And my engine's going very well indeed. |
| Lawrence Slater |
| "What is a jock strap? A nut case". LOL Guy. I'd forgotten how funny that was. ;). |
| Lawrence Slater |
| Guy Just blew the pic of your piston up for a look Firstly Pistons aren't round, they are cam ground and are wider across the thrust sides where the load is on them than they are if measured parallel to the gudgeon pin Lots of pistons are even flat in the area near the end of the gudgeon pin The burnt on oil on your piston is mostly mileage related and fairly normal BUT in your case, if that is how it came out ,the oil ring gap has been positioned near the gudgeon pin which is wrong If the end gap of the oil ring is positioned above the end of the gudgeon pin you run the risk of excess oil that accumulates at the ends of the gudgeon pin being pumped up through the gap causing oil burning. Also as the engine wears through mileage and the ring gaps increase, the blowby through the ring gaps can burn the oil onto the piston and if that gap is above the gudgeon pin there will be plenty of oil there to do just that If you have an outside micrometer,and know how to use it then the telescoping inside gauge set for 12 quid are a bargain and easy to use Just poke one in there and finger tighten the knob, check the feel of it in the bore where you are wanting to measure and pull it out and measure it with your micrometer Important to get the feel/tightness the same on the mike as with the gauge in the bore though There would be plenty of machine shops using these If you are on a budget-you can clean a piston up and use it in the bore with a feeler gauge to simply check the skirt clearance in several places up and down and around the bore quite accurately - If using this method always make sure you measure across the thrusts of the piston though remembering that pistons aren't round It always pays to measure skirt clearance anyway just in case you have a piston that's collapsed Honestly though, I'm inclined to agree with Lawrence If it's been going ok without any noises , a hone and a set of rings and bearings as required and away you go Just depends on how excited you want to get about it willy |
| William Revit |
| Thanks Will, I really appreciate having a "proper" Engineer's input on this (no offence to other contributors, whose advice I also value!) I have never had any sort of engineering training so what I know is self taught, picked up on the fly etc. Never-the-less I have messed with cars and bikes for over 50 years and rebuilt many engines in my time. In the past, and without the opportunity to discuss with others on a forum such as this, I would have just got on with it, making up my own answers as I went along. And I haven't had any calamities yet! That said, even having enjoyed far too many birthdays, I am interested to learn and to try out advice from those who know what they are talking about. So I treat this as an opportunity to try some measurements and experiment a bit. Just not quite as radically as a certain gentleman of Missouri might contemplate! I built his engine about 18 years ago. I know I would have staggered the ring gaps, and think I would have avoided the oil control ring being too close to the gudgeon pin. I may have focussed on offsetting just the compression rings and thought less about the oil rings. But I suspect they have rotated whilst I have been handling it. |
| Guy W |
| Interesting about the oval pistons. I didn't know that. I have an external 2"-3" mic. Measuring piston diameters in line with the pin and then across the thrust diameter: At the crown its near to a true circle. - 2.789 and 2.792. Just above the gudgeon pin it reads 2.791", and 2.807". At the base of the skirt it reads 2.797 and 2.809 I don't know what you make of that. It appears to be circular at the crown, but rather than being flattened at the sides, it is the thrust diameter that increases going down towards the skirt. I think I am measuring accurately. I get consistent repeat readings and also have an unused piston of the same specification that gives the same results. |
| Guy W |
| I've been looking to order bearing shell sets. Obviously mains have an oil feed hole, but why do the big end ones have holes as well? As an aside, Austin 7s have an oil feed hole drilled on the lower yoke end of the con rods. The (slightly) pressurised oil feed is forced out of orifices in the block, designed, rather vaguely, to squirt streams of oil. This is supposed to be caught by the holes in the con rods as they spin past with the revving crank, and feed through onto the white metal bearings. Primitive! |
| Guy W |
| Isn't there a hole in the conrod near the big end fed by the hole in the bearing shell to squirt oil onto the bores? Rob |
| Rob aka MG Moneypit |
| No, no corresponding holes in the rod. At least not on mine! I guess the holes in the shell help to spread the oil film over the crank surface from the crank feed hole |
| Guy W |
| I have a feeling that some of the small bore engines do have a hole in the rod. The bearings are the same. |
| Dave O'Neill 2 |
| I'm thinking so as well Dave I'm sure I've seen an A series with oil squirters Lots of engines have them but not all It's usually a fairly tiny hole compared to the hole in the bearing shell like 10- 20 thou. ish Some Nissan engines and a lot of diesels have actual squirter pipes at the bottom of the bore squirting at the thrust side and some cars like early Jags had a hole right up through the conrod to feed the gudgeon pin with oil Guy You are correct in your measurements The area from the top of the piston, down past the rings to the top of the skirt is usually a couple of thou. smaller diameter than the skirt and can be round or oval/ -This is done to allow the piston to rock a tiddle in the bore and stop the rings seizing in their grooves. -It also allows for expansion as the top is where all the heat is generated Years ago we had trouble with some of the big bore Ford V8 motors rattling on light throttle and the fix was to pull the pistons out and spin .003" extra off the ring area to stop it rattling on the bore---worked fine Your measurements give roughly one thou. ovality which isn't much,but given the small bore size I guess it's probably all it needs The piston makers know more about this than we'll ever know so we just have to trust them On the subject of skirt sizes,- yes it is quite common for the bottom of the skirt to be slightly larger than the top of the skirt--A new piston usually has the bore clearance marked on it and it will read for EXAMPLE -.0015 TOP -or, and I stress for example only -.0015 BOT This figure is the bore clearance for the piston and is measured at the relevant / marked position for that particular piston set being top of the skirt or bottom of the skirt.--If it has a size on it but no top/bot markings it means the skirt runs down straight without any taper at all and can be measured top or bottom On some of the Nissan engines the pistons are very lightweight and have hardly any bottoms on them at all The skirts are like a blade probably about 20mm wide Bore clearance for these is measured right at the top of the skirt and the bottom of the skirt is actually bigger than the bore.- At assembly time you have to actually push the two skirt-fingers together with your thumbs to even get the things in the bore--different Having an unused piston to compare your measurements is great and if you are getting the same measurements it sounds like your pistons are in good nick better stop now willy |
| William Revit |
| Wow, Willy ! And there was me thinking a piston was little more than an upsidedown paint tin that went up and down a short length of drain pipe ! I have cleaned up that piston and apart from some light scuff marks on the skirt on the thrust side it looks like new. I just need to check and clean the other 3 and check the bores for damage. Oh and source some new rings - l have a couple of enquiries out on that. |
| Guy W |
| The only think I would add, ring gap position is a red herring. Rings rotate at a rate of approx 1 rpm per thousand rpm, faster with a steeper crosshatch pattern and slower with a shallower crosshatch pattern. When an engine is stripped it does not show the position of ring gaps on assembly. To underline the proof they do turn, two strokes have pins in the ring lands to prevent rotation as the rings snap if the ring gaps end up on any of the transfer or exhaust ports. You must ensure you have a good crosshatch on your bore before you re ring. Let me know if you struggle to get rings Guy and I will ask around for you. Peter |
| Peter Burgess Tuning |
| I'm not an engineer either, but from my own experience, looking at those pistons, and taking Guy's description of the bores, and the now cleaned piston, -- I'd just give the bores a light deglaze, not worrying much at all about a cross hatch pattern, and assuming you can get the rings, I'd just put it back together again. If you hadn't said you will be happy with 30k miles, and instead said that you want a definite 100k plus from it, I'd say grind the crank, and bore it to +40 with new pistons. But having said that, my engine has done 120k miles. I've put another set of rings on it (re-using the oil controls), 1300GT head, and 19320 cooper-s pistons, I'm getting over 200psi compression in all bores. I see no reason why I won't get at LEAST another 60k miles from it. The thing about being a pro engine builder, as in being a pro anything, you feel the need to do it 'properly'. Indeed you have to, because you are charging people to do it properly. However, not being a pro, gives one a lot more leeway, and again from experience in many different ventures, shows that there is a great deal of tolerance in things. Specifically in A series engines, you can get away with comparative murder, -- very effectively. |
| Lawrence Slater |
| Staggered ring gaps. The blurb that comes with the rings, tells you to stagger them. So I guess it must be importnat, -- at least at start up. But this is VERY interesting. "Well, now you know. All rings are free agents to rotate as they like, making staggering of gaps on installation a joke and ring gaps are not a problem provided that the gap is not the manifestation of reduced ring radial thickness caused by peripheral wear. In the light of the logic expressed in this article we are offering an expensive prize to anyone who gives us a good reason for staggering ring gaps on installation – a free burial at sea." http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php |
| Lawrence Slater |
| When does it become bodging Lawrence. There is a good chance the bores are not round or parallel from use. It would be well worth while having the block honed with proper stones to restore the shape. For the sake of 20-30 pounds it would be good. The sad thing is, I get to see the do-it-yourself stuff that goes wrong and costs money to rectify, you have got away with it Lawrence which is great and somewhat lucky. It doesn't mean the next man will. I get to see the ones where the statistics stack up and it all turns to poo! Peter |
| Peter Burgess Tuning |
| The reason I said I only wanted another 30,000 miles out of it was to emphasise that what I want to do is a refreshment of an engine, not a full rebuild. I was not wanting a lot of advice on rebores, skimming heads, magnafluxing and fitting rocket launchers! In practice I would expect rather more than 30K, but not 100K It has has only done 80,000 miles since it was done to a good standard last time - ie a proper rebore, new pistons, all parts replaced with new, and using decent quality items. And very specifically as I think this makes a very big difference to an engine, the crank flywheel and damper were balanced as a unit and the block was line bored. With a moderately lightened flywheel it has always run very smoothly. And then, at my age and with the reduced annual mileage - down to about half from the regular 12K I used to do in this car - I am most unlikely to need another 100,000miles out of it! |
| Guy W |
| Everything you just posted Guy, is precisely why I said what I said. Peter, 'bodging' does not mean to do a bad job. Quite the reverse. But to re-ring an engine, is not to bodge it anyway. The rings are made and supplied as replacment items, where their use is appropriate. I haven't '"got away" with anything, which implies in the context that you mean it, that I've been very lucky not to have seized or blown up the engines that I've re-ringed. -- DOZENS, and they've ALL been fine. As amazing as you may find it to be, I'm not a complete f*cking idiot, and I know EXACTLY how to rebuild a SIMPLE engine, like an A-Series, so that it doesn't blow up within a few miles. You may be a truly great engineer Peter, and by all account you are, but please don't suggest that ONLY a chap like you can build an engine properly, and that a "do-it-yourself" effort will almost always end in tears. Here's one bodge then that you'll truly hate. Amongst the cars I've owned, was a Rover 2000. Not the 2.2TC I also had, but a bog standard 2000. It was endy, and the oil light kept flashing. I only had the road to work in, and no means to pull the engine. But I could get the sump off. It didn't take long to spot the knackered journal. Using some emery, and just my eye to decide what's what, I bought some new shells, and polished the scores out of the journals, backed the shells with silver foil to take up the gap, and bunged it back together again. I got over 2 years out of that car before scrapping it due to RUST, not a blown up engine. :). |
| Lawrence Slater |
| I am not going to get involved with arguing with you Lawrence, I find you have no tolerance for anyone elses views at all so I bid you all a fond fair well on the MG Enthusiast site and let you Lawrence tell everyone how to do engine work, vote and how their religious beliefs should be. You have driven a lot of folk away from the threads and I am yet another one. Peter |
| Peter Burgess Tuning |
| I didnt read to much of the above so this may be a repeat of someone elses thoughts the photos and discription looks great and well cared for... if you wanted to just deglaze and add some new rings... i dont think you would see any problems even tho the bearings look good... id be tempted to still replace them esp considering there cost .... its like tappets ...allways replace when you pull them no matter how good they look but i tend to be overly causious on projects like this btw... it might be a good time to lighten and balance the con rods if not done so and the harmonic balancer prop |
| Prop and the Blackhole Midget |
| Peter, don't go! There are many more people here who value your input and friendship far more than any who decide its smart to have a go at you. And Lawrence, for goodness sake just calm down a bit! There really was no reason at all for that outpouring of venom! |
| Guy W |
| Here's a link for you Lawrence ;-) http://tinyurl.com/h4mmhcn Hi Prop, yes we are on the same wavelength here. New rings, and new bearing shells will sort it I think. A sort of Mid-Life Makeover rather than a full reconditioning. But I won't be lightening the con rods. They were matched for weight when the crank/ flywheel and harmonic balancer were lightened and balanced. I don't want to risk upsetting that now by getting the con rods lightened and its really not necessary for my type of use. |
| Guy W |
| A bit of thread drift... that iowa hillbilly engine rebuilder from about 2-3 months back rebuilding the 1275... is about to have a really bad day on you tube coming up he got new pistions ... the AE 21251 low compression pistons and gapped the rings from the haynes manual for the bmc 4 ring spec instead of the AE piston spec he is off by .004 to .006 (eye ball variance ) his good friend no named advisor reassured him the spec is fine AE rig gap is .12 bmc 4 ring ring gap is .16 |
| Prop and the Blackhole Midget |
| I will repeat Guy's request Peter Please do not go away and leave us, I/we value your friendly input Always have May I add it is nice to see our old mate Les is still casting a fatherly eye upon us along with Willy and the others |
| Bill sdgpM |
| But I won't be lightening the con rods. They were matched for weight when the crank/ flywheel and harmonic balancer were lightened and balanced. I don't want to risk upsetting that now by getting the con rods lightened and its really not necessary for my type of use. yepp... i have to agree i didnt catch that part of your discription just another thought... if the head has to be skimmed more then you like or the local fuel gets to watered down and you need a lower compression to compensate the comtic head gasket is really top notch... i had a bit of an issue at 1st... but once over those hurdles it really is a great product it comes in alot of differant thickness..from a few .001 to around a 1/4 inch thick |
| Prop and the Blackhole Midget |
| Thanks Prop, about the Comtic gaskets. I haven't cleaned and really checked the head yet but I was hoping not to have to skim it as I am already on about 10.5:1 compression and that is quite high enough as it is! If the surface isn't good, then perhaps the Comtic may be the way around that. I have just removed the other 3 pistons. They are generally rather better than #4, with slightly less blow-by showing on the piston sides. And at first glance the bearing shells look better to - I cannot see any copper showing at all on these 3. I started just with #4 as from past experience it does seem to begin to show deterioration first. Something to do with the engine dynamics I guess, or maybe the slightly less efficient engine cooling at that end of the block. I also took off the centre main cap and bottom shell. It looks good, as do the thrust washers. But I will need to clean them all up to get a proper look, and maybe try some measurements. |
| Guy W |
| What did i miss ? Was it those damn candiaians agian....haha Ill have a full read later today.... what ever the disput it cant be that bad to go all nukular my understanding for staggering rings is if the gaps are lined up on a new engine during break in (1st 5000 miles ) is the meshing of all the parts creates a great oppertunity for a groove in the cly... granted alot of varibles happen but why risk it plus even though all the rings rotate id think they would move in the same direction and at the same pace causing some kind of cork screwing grove is my guess |
| Prop and the Blackhole Midget |
| Whoa there people, -- and Peter. Firstly Guy, I don't need your link. If you and anyone else had looked closely, my last character in that post was ":)". You peter, chose to attack me. Quote " When does it become bodging Lawrence" Quote " "you have got away with it Lawrence which is great and somewhat lucky." What? I'm not allowed to comment on that? Cobblers. Like I said, I'm not a f*cking idiot. I'm not lucky, I know what I'm doing, irrespective of whether or not you think so. Am I leaving the site because you don't agree with me? LOL. You want to have a tantrum Peter, go ahead. I was posting my opinions on what Guy could do with his engine. If you or anyone else thinks that is telling anyone how to do anything, you have a problem, not me. You and everyone else is free to ignore EVERYTHING I say. God? Voting? Get a grip man. And if you're all completely pissed off with me, well you know what you can do. Complain about me, and have me expelled! I'm sure it should be easy enough. Pathetic. Nope still not angry at all. Highly ammused is more like my emotion. lol. |
| Lawrence Slater |
| Back to ring gaps. I dug out three old different ring maker's leaflets. Cords, AE, and Grant's. In all three instruction sets, gap placement is only specified for a multi-segment ring. It isn't specified for single segment rings. I know from experience, that the multi-segment rings, whilst they may well rotate as a unit (I hadn't realised that until reading all below), the segments don't rotate against eachother. So at least for a multi-segment ring, the gaps should be spaced. But does it matter where? Grant's ring instructions go further. They stipulate, for the oil control 3 segment ring, -- "Install expander-spacer in ring groove directly above wrist pin hole. -- (gudgeon pin hole to me ). I can't remember at all now where I first heard or read about ring gap placement. But somehow it seems odd to line all the gaps up. And since it costs nothing, requires little extra effort, I think I'll go on spacing all my ring gaps, just for the hell of it. Glaze busting. What do you use? I use this flap wheel. It's actually the very tool suggested/sold by Cords. I've had it for yonks, probably 35 plus years. The tips are worn, so I tape a fresh bit of 280 grit paper to one flap, and run it up and down the bore a couple of times. It's served my engines, and loads of others over the years, very well indeed. I love a bit of precison engineering, Don't you? ;)  |
| Lawrence Slater |
| Well Thorntons have been good, and after exchange of several e-mails have offered a set they think will fit. 1/16" compression rings will be fine but their suggestion of 4mm oil control I think will be a tad too tight (groove measures at 3.94mm)unless there is some tolerance built in. Main problem is price. At £80+VAT they are more than I can get a new set of ringed pistons for! Pity as these pistons are looking good, once cleaned up.  |
| Guy W |
And piston top
 |
| Guy W |
| Yup Guy 90 quid plus for rings. BUT. Can you get a +30 set of pistons? I couldn't find any, and didn't want to re-bore. Have you looked at grants catalogue? Compare their ring depths and widths. They may well have a set to fit. Actually, I just noticed. Sussex sell a bog standard 8:1 +30 piston. I remember now, I didn't want a bog standard piston instead of my Cooper-s pistons. So I bought Gran't rings. |
| Lawrence Slater |
| The quote I have from Thorntons is £80+VAT for a set of Grants rings, like yours. You said you got them for £35 didn't you? |
| Guy W |
| Sussex Classic Cars: 1 x PISTON SET +30 - 1275CC midget £92.58 £92.58 Problem that gives me is then having to R & R the pistons from my present con rods and little end pins. And the possibility of having to deck the things as well! |
| Guy W |
| I bought my Grants rings from a place in Kent. http://www.psautoparts-store.co.uk/ They're fairly near me, so no post. I'm hunting for my receipt. I seem to remember, I looked at the Grant's lists, premier ordered them in for me, and I collected them. Definitely circa 35 quid. You know what a tight sod I am. Did Thornton name the Grants ring set? If they gave you a Grants number, you can use that to order them. It may even be the same set I got. It's actually a 4 ring set. I discarded one of the compression rings as mine is a 3 ring piston(top comp' rings the same). No ridge dodger though, so you need to make sure the lip at the top is slight -- as mine is. I'll dig out my grants box number. |
| Lawrence Slater |
| No he didn't give a Grants number. I was asking for a "best price" and he just said "the only match he could find were Grants from America and they are expensive" PS I think you may have been adding your reference to Classic Cars' s pistons as I was typing. I read your message but didn't spot that line on the first time of reading. Often wondered what others see on this when one is adding an edit. |
| Guy W |
| Still looking for my receipt. But here's my box. Google grant's rings. There's a pdf with the set numbers, and ring dimensions. G1280-30 or P1280-30. Your pistons are for a 1275 Austin. The crown shape and height above the pin may be unique, but the grooves will likely be standard. The only thing to take note of, is the DEPTH of the grooves. You may have SHALLOW grooves, as my 19320 piston bottom groove does. Give Premier a call and ask for a price.  |
| Lawrence Slater |
| Meanwhile, an interlude for Glaze busting -- again. If you love glaze busting, you'll love this. "CAREFUL WITH THAT HONE, EUGENE! Synopsis: There is NO such thing as "Glaze Breaking." That's because there's no such thing, in a cylinder, as "glaze" - the word implies a deposit of foreign materials of some sort on your cylinder's surface. Unless you've been running with Teflon in your oil or some such silly thing as that, from whence would the foreign materials have come? Cylinders don't "glaze." Brake drums glaze - brake shoe material can actually become deposited on the drum surface, but cylinders don't. No, what you've got is a smooth, polished, machine surface - just the thing for your new rings to seal against, once their high spots have been rubbed off in a careful and responsible break-in process. One which does NOT need to be preceeded by using the crudest of all the machine tools to scratch, abrade, trash, dog, bullyrag, and otherwise screw up your lovely smooth cylinder. " Read on and enjoy. http://www.snowvalley.20m.com/bikes/dnthone.htm |
| Lawrence Slater |
| Guy. This might be of interest. http://www.grantpistonrings.com/products/rings/ring_styles.htm |
| Lawrence Slater |
| And this. Click on the BLMC variants. Lists the ring sets with dimensions. http://www.grantpistonrings.com/catalog/index.php |
| Lawrence Slater |
| And here's a link to DEEVES rings. http://www.deves.com/devesrings/cars_AUSTIN.php |
| Lawrence Slater |
Maybe this helps. |
| Lawrence Slater |
| Guy, TRW are now Speedpro. Yyour pistons appear to be standard in Metro Turbos. http://www.deves.com/devesrings/cars_MG.php Scroll down to Metro 1300 and Turbo. |
| Lawrence Slater |
| Thanks for all the lynx Lawrence. I am out at the moment but will check them later on the computer when l get back |
| Guy W |
| In the states ...in my experiance deves is the ring of choice for the 1275 there is another option for rings that may be interesting... "gapless rings" Trevor jessie turned me onto them ... i didnt go that direction but wish i had just for the uniqueness of them esp for the 1275 that suffers deeply from blow by lawerwnce i wasnt sure i followed your comment about glazing... i know of several examples of glazing... and yes your partialy correct ( probably because you hate muslims so much ) ... but i know of new engine builds where new tech oils that fights wear is used and the engine is baby ed and so no intial wear is introduced so the rings never really seat and the anti wear oil gets cooked onto the cly walls and whola ... lots of blow by on my old toyota 22re engine that had around 275xxx miles when i pulled the head had alot of glazing polished look on 5here cly walls but it held good compression but did piss alot of oil out the front crank seal.... never burnt it... so something to be said for glazing over the long haul vs glazing in a new engine prop |
| Prop and the Blackhole Midget |
| Guy something ive noticed ... low compression on one cly due to general wear and age ... seems to always be on #4 then #2 I wonder if that occures because of the weight of the flywheel... it dosnt explain on #2 ... but if there is block flex meaning there is some give and the crank acting as a lever with a anchor attached one end id think there has to be some kind of extra oblong canterlevered wearing going on in the rings of #4 Just one of my prop moments of deep 1275 thought... haha prop |
| Prop and the Blackhole Midget |
| Lawrence, I have been looking through your links (or Lynx as my not-so-smart phone would have it!) Useful stuff there. From the Grants catalogue your ring set P1280, or C1280 (C for Chrome, not G, BTW) are listed for an Austin 1300. It then lists the rings sizes as 3 X 1/16" and one at 5/32" There is a separate listing for a Sprite MK1V which lists rings as metric sizes,3 X 1.5mm and 1 X 4.0mm Although my car is a AH MK1V they are replacement pistons and therefore not necessarily these metric sizes. The bloke from Thorntons didn't give a box number so I cannot be sure what he was looking at but he said they were 1/16" compressions and 4.0mm oil - so he was mixing his units. Grants don't list a mixed unit set like that so either he was being imprecise or he was offering to make up a set. Frankly I don't think the latter as I did comment that the 4.00mm oil rings looked to be too big for the groove dimension I had given him. I was not sure if mine were imperial or metric pistons, but measuring the grooves with my cheapo digital calliper gauge they are 1.66mm and 3.96mm. Using an online conversion app. 1/16" is 1.59mm and 5/32" is 3.968 so it looks like mine are indeed imperial sized versions. I think the metric ring sizes of 1.5 and 4.0 would be too slack and too tight, respectively, so ruling them out as metric pistons. From all of that, it would seem that the 1280 set that you got would also suit these pistons of mine. P and C refer to plain or chromed rings. Do you know the Pros and Cons of P and C rings? |
| Guy W |
| And thanks Prop. I like your train of thought and you could be right. But on mine #2 is no worse than #1 or #3. But then I do have a lightened and balanced flywheel so maybe your speculated leverage effect on the block would be reduced in my case anyway. It is only #4 that shows more blow-by That's why I thought about the slightly less efficient cooling at that end of the engine which I understand is a known truth. |
| Guy W |
| Lawrence, Now going on to the Deves link you posted. I don't think mine match their listing for Metro Turbos which have only 2 imperial comp and a metric oil. Mine need 3 comp rings which matches their listing for a ( it may be that as the difference between imperial 5/32" and metric 4.00mm is only 0.04mm they are considered the same size?) But it does look like their entry for a MK111 Midget, set 1265. That is a 4-ring set. So far, none of these catalogues that I have looked at list the over bore sizes, so I don't know if the part numbers would be the same, but then specify +30, +40 etc. The Grants box in your photo just seems to tag the 030 size on the end of their part number. |
| Guy W |
| Lawrence, I now see that the alternative G1280 P/N you mentioned wasn't a mis-type of the Grant C1280 as I thought, but is the part number that PS Autoparts list for the ring sets they supply, manufactured under the name "County". County products seem to be made in various parts of the world, India, China, Eastern European countries, - - - PS do list these County rings at what looks like the correct sized at £36 and list a +030 option. Searching via google, County rings and pistons seem to be quite common although I found just one thread about poor quality concerns. Seems they charged you the same price for a Grants set as they normally charge for Countys. None of the spec. data I have looked at so far mentions the depth of the rings/ grooves. |
| Guy W |
| Hi Guy, Just had a read through. Definitely G.1280-30. See pic. My memory isn't what it was ( and unfortunately I lost almost all of my late 2014/early 2015 emails, when my laptop failed and I restored from an older data backup), but I do remember now an email conversation, followed by a telephone call to Thorntons. As well as the price, I managed to get a ring set number from them. I think I used that, along with the various catalogues, to find the Grants set. And again you seemed to have jogged a memory. I think I found that "G" number in PS too, ordered them, and was surprised when I got there and it was a Grants set instead of a County set. P-Supplies are really helpful. Although you'd have to have them posted, they were happy for me to order them, inspect them, and return them if they weren't what I needed. As for County. They've been around for yonks too. I reckon they'd be fine. I've been trying with no success to find a phone number/web address for County. Who/where are they now? Chrome vs Cast. I think chrome is for more 'modern' engines, where there is less oil in the bores, and are more suited in a new bore. Cast wears and seats better in a worn bore, so better for a re-ring. Also cast is cheaper :). And since that's all I've ever used on my re-rings, cast is my choice. Even newer are 'moly' rings. Again modern engines have and need less oil in the bores. Chrome is probably too hard four our bores too. --- Something else to study up on now. lol. Try calling these people. "Red Lizard Classic Car Products" 01624 814231 http://www.classiccarproducts.co.uk/classic_car_parts.shtml "Piston Rings We stock ring sets and individual compression and oil rings in many different brands, but primarily hold a vast stock of Hepolite and AE product. Like many of our other product ranges we can supply a wide range of oversizes. Our great strength in this product is the ability to supply loose rings off the shelf or have rings manufactured to size for special requirements . We can also source loose rings to make up complete sets which can no longer be purchased under a complete part number." ---------------------------- Ring depths. Since I didn't use the oil controls that came with my grants set, I can measure the depth of them. You can compare that to the depth of your oil control ring. I didn't have any trouble with the depths of the compression rings, and as I still have the ones I took off the pistons, albeit that they are worn, I'll measure the depth of those too. They won't be THAT far worn, so it should be possible to see if they match the depth of your compression rings, and hence the depth of the compression grooves in your pistons. Metric vs imperial. My understanding is that there is a distinct difference between metric and imperial sized pistons. The trouble is, identifying which we have. Are the new pistons supplied by Sussex, metric or imperial? BTW, he supplies COUNTY pistons as far as I know, and they are considered to be a good quality copy of the original Hepolite pistons. Interestingly, looking at the PS catalouge, -- I have a hard copy of it -- they list a 3 ring set G1251 -30, that they describe for the 'late' hepolite piston. But what date do they mean by 'late'? And it's metric. I wonder if it would have been a better fit on my 19230 hepolite 3 ring piston?  |
| Lawrence Slater |
| PS supply COUNTY pistons. Also, looking through my hard copy of the PS catalogue -- I think COUNTY, must be a Firstline/Unipart type of operation.  |
| Lawrence Slater |
| Maybe one of the Pro engine builders can step in here, with any specialist knowledge they have, regarding the groove depths on pistons. They must have been pretty standard for most factory stuff for the period, and differed only on after market pistons. This is bourne out by something I read in the paper intructions that came with the Grants ring set. I'll photo it, but it has a distinct note about this ring set groove depth, perhaps not matching an aftermarket piston. |
| Lawrence Slater |
| Hi Lawrence, It's quite a detective story! When you noted yours as G1280 I looked on the Grants catalogue and could only find 1280's with P (pain) and C (Chrome) prefixes. So I assumed a mistype or maybe you were reading off a damaged / obscured label and took a C as a G. Clearly, neither of those things! Then looking ta the PS Autoparts website I see that the County brand uses the part number G1280. County seem to be a collective brand name, possibly selling items supplied to them from a wide variety of manufacturers. I wonder therefore if they actually source the rings for their County pistons, from Grant? (addendum: cross posting again!) As well as the spare piston, box and leaflet for my TRW pistons I realise that the paper sleeves that the original rings were in actually carries a different logo - a pair of dividers with the letters PC in an oval. PC was the Perfect Circle company, a major manufacturer of rings. I don't think they still exist as such, but were taken over by MAHLE which I think is predominantly based in America. They clearly still sell piston rings but I haven't yet traced through to a likely UK supplier to contact. Actually, I don't think I need to. I have enough information now. Any 4-part imperial 1/16" + 5/32" set is likely to do. The only unresolved variable is the ring depth - and the price! |
| Guy W |
| Ah yes a "pro engine builders" perspective would be great - oh wait we just lost one............... |
| a reid |
| Ha. Very interesting stuff Guy. Ring groove depth -- and widths. http://www.hotrodders.com/forum/piston-ring-oil-control-groove-depth-216524.html Have a look in the w/shop manuals too. http://austin-healeys.com/austin-healey-sprite-m-g-midget-a-series-engine-details/ Ring clearance in groove -- (Width) 948 cc, 1275 cc (top, second and third) .0015 to .0035 And, this from Paul Walbram on here back in 2011 in reply to me. "Rings should be easy emough to get. Be aware there are two thicknesses of compression ring - 1.5mm and 1/16". They are aproximately close but not near enough to be the same here. Original midget would have been 1/16", while the Metros by at least the mid '80's had the metric rings and high compression pistons with a shallow dish. One of the part no's is BHM1284 (plus the oversize) - I'm not sure whether 1/16" or 1.5mm but suspect 1/16". 1.5mm rings can be hard to find, if you get stuck let me know. You need to check the clearance between ring and piston down the side of the groove. It usually starts at around .003", if worn the book figure is that if you can get a .006" feeler more than 1/16" into the gap between ring and land then you need to do something about it. This could be either new pistons (preferred) or by widening the groove to take wider rings or the original rings with a spacer. If you have metric rings, then taking the approx .004" out to fit 1/16" rings can provide a neat solution to moderate groove wear. Paul Walbran" Also, set of CORDS +30 here for 25 quid inc postage. NOS. http://www.ebay.co.uk/itm/1275cc-MG-MINI-MARINA-1300-ALLEGRO-piston-ring-set-030-/272119886021?hash=item3f5b9bf0c5:g:i58AAOSwFMZWrNC7 Message the bloke and ask what depth the rings are. Set is 827, that's the same as I first used on the original 4 ring pistons in my other engine. Your TRW pistons are a high/comp version of the originals as far as I can see. These may well fit. --------------------- Edit. A reid. His choice and fault, not mine. Nice to know others following this too ;). |
| Lawrence Slater |
| Guy, I think Mahle are still based in Stuttgart. Their blurb says they've just produced their millionth diesel engined car piston. They produce a lot of stuff for old VWs so if you need a seond or third fall back plan you might want to call one of these guys to see if they're able to help/advise. Coolair http://www.coolairvw.co.uk/Category/0/Shop_by_Vehicle~Baywindow_Products.html or VW Heritage http://www.vwheritage.com/shop/bay-bus |
| Jeremy Tickle |
| CHROME rings. --- According to the BMC workshop manual, -- they used chrome faced cast rings when new. Also the BMC w/s manual gives the thickness(depth I assume) measurements of the rings. This is for the 1098, but the way the w/s manual works, is that it's is only mentioned again later, if it's different for the engine of a bigger size. I'll check this against my new unused oil control rings, and my old compression rings.  |
| Lawrence Slater |
| Ah yes - admitting fault is the first difficult step in being able to move forward and get help http://tinyurl.com/h4mmhcn ;) |
| a reid |
| Yes indeed a reid. Guy linked to that. You're a loooooooooong way behind the curve. Also, I suggest the leaver might like to read it. :). And you might like to read the posts properly, so that you understand what you are talking about ;). But if distorting facts amuses you a reid, go ahead, knock yourself out. It's all good fun. lol. I don't suppose you happen to know anything about ring groove depths do you, or anything else constructive? I'm guessing not, since you haven't mentioned it. ;). Meanwhile, any pro-engine builders who care to add their input, if they have any specific information on ring depths, won't be helping me in the least, -- they'll be helping Guy. Back to ring depths. Here's what the Grants leaflet says. (see pic). (Interesting they mention the top ring being 'moly'. But then again, they have a picture of example rings, and it doesn't include the 3 segment oil control that was in the packet. So that may simply be a general leaflet, to cover all. But it is right about the shallow depth on my oil control ring groove). As for my rings -- depths. The UNUSED compression ring that came with my set (I only needed 2, there were 3) has a depth of 2.7mm. I measured one of the used ones that I took out. 2nd compression ring. It measures 2.54mm. Quite a bit of wear there, assuming they started off at the w/s manual figures. The oil control rails (new unused) that came in the Grants set, measure 2.86mm. BUT, they sit ON TOP of the rear upright lip of expander ring (3 part oil control ring - 2 rails and one expander). Taken together the rail and expander depth is about 3.2mm. Which is why I couldn't get the piston down the bore with the new oil control rings fitted. So I re-used the existing oil controls. And that takes me at least full circle (no pun). Ideally, money no object, you'd rebore and fit new pistons, because of the hassle finding the correct ring set. But, since like me, you don't expect to drive another 100K plus on the engine, a compromise can work. I reckon new compression rings will take care of the excess blow by, and your existing oil controls will then be ok -- assuming you have shallow grooves too and can't fit the new ones.  |
| Lawrence Slater |
| wooooh wait a minute... I thought one could just put a smiley face, wink or a lol at the end of a comment and that meant they wouldn't take the hump but even with a wink i'm now slow, cant read properly, dont understand what i'm talking about and I distort facts (fact being used in the broadest sense of the word I assume, or facts according to King Slater and from my shortish time on here I feel they are both one in the same). That being said I did fully deserve a Lawrence put down there as I was genuinely having a dig at you . Much as I try and ignore your posts, due to reading quite a few of your previous rantings, sometimes its necessary to read them as part of the flow of discussion. Then on occasion i get fed up with your arrogance and attitude to others that you disagree with. Maybe its just me. No harm no foul. I wont lose any sleep over your comments as I'm sure you wont over mine. Oh and just for the record - do I know anything about ring groove depths - no I don't (hence I was reading the thread (albeit not very well according to you). Do I know anything else constructive - yes I do. PS - you really missed the reason for me re-posting the link and the comment but I wont hold that against you, you could always try reading it properly - smiley face omitted. |
| a reid |
| A R of Lanarkshire, (I presume R is short for something?) I had posted the self same link earlier on when Lawrence had a bad reaction to something Peter Burgess said. I chose that one as I thought the location might be convenient to Lawrence and also thought that he might tick the boxes for many of the clearly stated benefits offered by the course: Experience improved relationships Feel happier and calmer Enjoy better health and wellness Feel less stressed Become more creative and productive Get on better with others Be able to express anger appropriately and stay in control Prevent yourself doing things you may later regret I too added a smiley which was ignored in Lawrence's response to me! Not that I mind. I thought it was funny even if he didn't! I have absolutely no problem at all with Lawrence's views on politics or religion, or his adoration of his God - who goes by the name of David. They certainly don't fit with my views but then I am pretty tolerant of other's beliefs. What I do dislike is inappropriate or aggressive language on whatever topic. So no problem with Lawrence's views, excepting that I cannot understand what makes him think that others want to hear them so often! For all that, I like Lawrence's willingness to help and offer advice. And mostly, I appreciate his "go for it attitude" and his interest in working out by experimentation why things do, and sometimes don't, work. For these reasons I wouldn't like to see Lawrence banned. I just wish he would be a bit less paranoid when others have differing advice to offer (like Peter) and learn to live a bit more harmoniously with others! Whoops! I forgot the smiley ;-) |
| Guy W |
| Guy I can totally agree with that - I was sure I was going to get a " shouldn't there be an S after A R." The names Alan (smiley face reinstated) |
| a reid |
| I considered it! The SE that is! ;-) |
| Guy W |
| Now, back to the proper discussion. My existing rings use a 3-part oil control ring - a grooved spacer (not a spring type) and two thin blades. The thickness of the spacer which shouldn't be worn at all because it doesn't contact the cylinder wall, is 2.2mm whilst the blades - which could be a little worn - are 2.28mm The blades sit alongside the spacer and there isn't any sort of lip on the spacer. |
| Guy W |
| Guy. The link posted concerning whether to brake up the "glaze" on the cylinder walls when installing new rings into an engine was interesting for a number of reasons. Having done some professional technical writing in the military and some non-professional technical writing in the civilian world, I do not find that article particularly well done. For a number of reasons. It might, however, be correct. But, it is hard to say without testing, as a minimum, three engines that have been re-ringed without honing and three engines that have been re-ringed after honing, for a period of several years with all being operated under the exact same conditions. No one has presented any proof of such testing (except Peter), so all any of us are offering is our best guess--an opinion. As we all know, opinions are like a certain orifice--everyone has one. Regardless of what you decide, do it with the quality and craftsmanship you did your original rebuild with. Make your own decision about what is needed, then, keep records of what happens. Eventually, you will be able to offer data based experience where others are simply offering their opinions. Bill. Thank you for mentioning my posting. I have admired your posts over the years, considered you to be one of the more knowledgeable people, and have enjoyed your laid back style of writing. I will miss you and a handful of people, most of whom no longer visit this site, as I go off to join Peter. Les |
| Les Bengtson |
| Ah well. More irrelevant thread drift to liven things up. " -- I thought one could just put a smiley face, wink or a lol at the end of a comment and that meant they wouldn't take the hump --- " Well there you go then a reid. Read the last character in my post Posted 14 February 2016 at 13:45:07 UK time. -- You may recognise it. You may like to explain it to Peter Burgess, for whom the link Guy first posted, would seem far more apt, since he displayed anger and left the room. I'm still here, in the pram, playing with my toys. You may even understand that I wasn't angry at all. But probably not. What you and others fail to appreciate, is that I don't give a rats ar*e what others think of me, or say about me. Water, duck's, back. But I do enjoy responding when someone has a go at me. Esp' when it comes out of the blue, when I haven't mentioned their name or referred to them, even obliquely. I've said before, I find all this amusing (BBS), as much as interesting. Nigel used to be a great sparring partner, but for reasons unknown, he doesn't post here anymore. Apparently nothing to do with me. And nope, you can bet yer bottom dollar, if I'm kicked by an ass, I don't lose any sleep wondering why. ;). King Slater? Only in OTHER peoples minds. I only talk 'slightly' less bollocks, than many on here. lol. LOL in caps for emphasis. And my assumption was correct then about ring depths. You haven't demonstrated the 2nd part to be true, since your much longer post, is entirely devoid of anything constructive. "PS - you really missed the reason for me re-posting the link - " Nope again. You seem to have missed that it could be interpreted and responded to, in a number of ways. I chose my response, and it too ended in a 'wink'. Oh no. Not again Guy. Lol. I didn’t have a "bad reaction" to something Peter said. I reacted, as is my prerogative in the circumstance, to the implication, that I was lucky that my "do-it-yourself stuff ", botches ( because that was clearly implied, even though the word "bodging" was used in error, which is something entirely different) hadn't resulted in my having to take my engine to a 'professional' to have it put right. Condescending, patronising bollocks. Now you might call that response venomous, whereas you were wrong to describe my first response that way. But you’d still be wrong, simply because, although I responded, I really didn't care that much at all. As I just pointed out again, I enjoy the banter, and anyway, it's giving me more practice typing. Experience improved relationships. I'm perfect, hence my relationships are too. Feel happier and calmer. I'm always calm, even when ripping out someone's throat. Enjoy better health and wellness. Just had a medical. 100% fit. – for an oldie. Feel less stressed. Any more chilled, and I'd fall over backwards. Become more creative and productive. Too f*cking lazy for that. Get on better with others. Don't like most people, wouldn't want too. Be able to express anger appropriately and stay in control. Always serve my revenge COOOLD. Prevent yourself doing things you may later regret. Most frequently, regrets stem from not being angry. Being angry and taking it out on the right person, is a great way to prevent regret. LOL. " -- a bit less paranoid when others have differing advice to offer -- " Seems to me, that point is best aimed at "others". I don't care what advice others give. I'll either note it and follow it, or I'll ignore it. After all, I'm arrogant and self opinionated. But only because I'm perfect and know it all. You've got me on the God/David bit. Who the f*ck is that? Does anyone want to hear my views? On anything, or even at all? Who cares? It amuses me to let them be known. LOL. |
| Lawrence Slater |
| Prop, Les's post has reminded me that I didn't respond to your post re- glazing. They weren't my words. I found that article online last year sometime, and looking for this stuff reminded me about it. There's a logic to it, because it's claimed that it was researched by the SAE. I've always deglazed, but that did make me wonder. Les. For the record. My opinions are pretty much all based on my experience. Why are you leaving Les? |
| Lawrence Slater |
| "Now, back to the proper discussion. Yes indeed. Halleluja. :) "My existing rings use a 3-part oil control ring - a grooved spacer (not a spring type) and two thin blades. The thickness of the spacer which shouldn't be worn at all because it doesn't contact the cylinder wall, is 2.2mm whilst the blades - which could be a little worn - are 2.28mm The blades sit alongside the spacer and there isn't any sort of lip on the spacer. " Then you may have the same problem I had. The 3 part oil control in the Grants set, DOES sit on the lip. But you can do exactly what I did. Re-use your existing oil control rings. My engine's running fine, and not smoking. If it does that for 60K miles, I'll be dancing. Do you by any chance have an old OE piston? If so, measure the groove depth, and compare it to your TRW groove depth. Anyone else out there happen to have an OE 1275 piston, that they could measure the groove depth on? |
| Lawrence Slater |
| Les, In a somewhat simplistic way, I thought the purpose of cross-hatching on a bore was actually to retain a little oil on the surface, which a highly polished finish wouldn't allow. Whether this is true or not I don't know but it sounds logical. I probably read it somewhere in print at some time in the last 60 years or so. I say "in print" because I am a bit old fashioned and tend to trust things I read in a good hard backed book more than things I read online. And that probably isn't logical! For low output engines it probably isn't that critical, but I will give it a bit of a hone to create some semblance of cross hatching before I re-assemble. Thanks for your input. But please don't you go as well! |
| Guy W |
| Guy, Oil retention was my understanding as well and modern manufacturers use plateau honing or lasers to cut the cross hatch pattern into the bores. |
| David Billington |
| <<Do you by any chance have an old OE piston?>> No unfortunately not. Pity as having one to check my TRW pistons against would have in one stroke side-stepped almost all of the issues I have raised. Many of the suppliers specify their rings by which engine/ year they are suited to. That's fine if you use original, or original spec pistons. If I knew my TRW pistons were to OEM spec, then life would be simple, but I cannot just assume that. |
| Guy W |
| A quick look for "laser bore honing" turned up some interesting stuff http://www.gehring.de/en-ww/laser-honing http://www.photonics.com/Article.aspx?AID=2304 |
| David Billington |
| Very interesting David. Although I think the laser technology may be a little beyond fitting in my cheap Lidle - quality pillar drill. But it does confirm that the principle of retaining an oil film on the bores is correct. <<In the final stage of honing, the cylinder wall receives a surface texture that is designed to allow a friction-reducing oil film to form>> Also interesting in their high-tech solution, is that the honing is concentrated on the top section of the bore where the rings change direction near tdc. That, rather than half way down the bore where I would have expected |
| Guy W |
| I have a book which goes into ring operation and it says that research showed that significant amounts of oil travel up past the rings but the critical factor to whether an engine burns oil is how much oil goes back down again. It depended on the ring external profile and if the ring allowed more oil up than down then it effectively pumped oil into the chamber and it burned, the opposite where it allowed oil back down more easily resulted in a low oil consumption engine. A fair bit of technical knowledge behind rings. They're not round either even though they look it, I haven't checked, IIRC it was Hepworth and Grandage that perfected the shape so that they apply an even pressure on the cylinder walls, a true circle wouldn't so that. |
| David Billington |
| <<They're not round either even though they look it>> If that's the case, then the idea of randomly staggering the ring gaps, or indeed Peter's assertion that they rotate, doesn't stack up. It may be of course that certain high performance engines do have these special out of round rings, but then they would also need to have pegs in the slots like the 2-strokes that Peter referred to. Some of the ring sets for A series that I have been looking at use a wedge shaped or tapered ring profile which suggests to me an adaptation to creating an oil pumping action by the ring. The whole topic is obviously far more complex than at first appears. |
| Guy W |
| Most of the pressure that holds a ring face against the cylinder wall, is compressed gas exerting force from BEHIND the ring. Some compression rings have a chamfer on the top of inner face, to increase this pressure. And since that pressure exists, it also seems to go against the rings rotating that easily. But assuming they do rotate, which way do they rotate, and why? None of which helps to get to the crux of the current matter. Does anyone have an old OE 4 ring 1275 piston laying around, that they can measure the groove depths in? In particular the oil grooves. |
| Lawrence Slater |
| Guy, Why do you think the out of round ring would effect ring rotation. The idea behind it is that when the ring is bent by putting it into a circular bore the shape is such that the bending forces are even all around the ring and result in a even pressure on the bore wall all around the ring. Quite right about the ring profile. Lawrence, Quite right about the gas pressure acting behind the ring, too high revs can result in the ring mass forcing it to seal against the upper ring land and loss of pressure behind leading to ring flutter IIRC, hence the Dykes pattern rings, only ever seen one in a small high performance 2 stroke though. Ring rotation direction, is this effected by whether you're in the northern or southern hemisphere ie the Coriolis effect. |
| David Billington |
| David I was visualising an out of round ring in an out of round bore, which would prevent it rotating. But I see of course that is nonsense! I don't think Coriolis force would effect ring rotation. But whether you drive on the left or the right would because that determines which way you accelerate around a roundabout. |
| Guy W |
| Guy, Sorry, very pertinent to this thread, I should have added a smiley after the comment about the Coriolis effect as it was largely added in jest. As I understand it the Coriolis effect is very small and not dominant in which way the water run downs the plug hole, its effect on ring rotation can be left for further debate if desired. |
| David Billington |
| "Does anyone have an old OE 4 ring 1275 piston laying around, that they can measure the groove depths in? In particular the oil grooves." yes, I do :-) but I'm not sure how best to measure the depth of the grooves, any tips? |
| David Smith |
| I probably do, too. |
| Dave O'Neill 2 |
| Yes David, l think l knew that ! ;-) l expect you know what a roundabout is ? |
| Guy W |
| "l expect you know what a roundabout is ? " Yup, and inconveniently added obstruction in the road that causes you to slow down when you don't want to. lol. Dave and David. I've got a depth bar on the end of my vernier calipers. Have you got one of those?  |
| Lawrence Slater |
| Ring roatation, and ring gaps. The plot thickens, and becomes ever more interesting. "Rotation of piston rings " "The speed of rotation of piston rings has been measured experimentally. Shaw and Nussdorfer (2) examined the phenomenon on a large engine and found that, at 1000 rpm engine speed, the piston rings were “observed to rotate as rapidly as 1 rpm”. Jung and Jin reported in more detail: on the engine they used, at 4000 rpm and 2 bar bmep, the rings rotated at 0.6 rpm in opposite directions to each other, with the second ring initially oscillating between two positions before finally beginning to rotate continuously." http://www.highpowermedia.com/blog/3954/rotation-of-piston-rings ------------------- And this next piece suggests that ring gaps don't matter much and too much attention is paid to them. "Ring Gaps vs Knowledge Gaps" "Frequently I hear in court that when an engine is dismantled it is discovered that the ring gaps were not staggered when they were installed. Frequently I read workshop manuals that go into great detail on the necessity to stagger ring gaps. Frequently these manuals specify ring gap limits – which is yet another myth we can bin before we are finished." ----- --- "Even worse is the preoccupation with the size of the ring gap. Yes, there is a minimum but this varies considerably depending on the material used. Normally 0.003"/0.004" per inch of bore size is given but where, for example, low expansion SG (spheroidal graphite) iron is used, it can be considerably less. It’s no problem if the gap is too small because it can, in the final analysis, be filed bigger but what do you do if it's too big? You cannot stick a bit extra in there! Well, the answer to that was that you melted them down and started afresh – until AE research asked the question, "What is too big?" and set out to quantify that. The results were interesting – very interesting – and what you are about to read was kept quiet because it bestowed an enormous commercial advantage on AE. This is probably the first time the information has been published although the research was undertaken in the late 1970's – almost 25 years ago. " http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php |
| Lawrence Slater |
| You know what it is? Resonant frequencies and harmonics. Everybody knows about Angers and Tacoma bridges. Marching and wind, at sympathtic frequencies has interesting effects. In those cases, destructive, and lessons were learnt, -- but not fully because they had to modify the millenium bridge. In engines, apart from the up/down movement of the pistons, there are also lateral and inline thrusts. I guess at the 'goldilocks' rpms, for each circumstance, all these combine to either keep the rings stationary, or rotate them one way or the other, or oscillate them. It's really quite obvious when you think about it. LOL. |
| Lawrence Slater |
| Well that is a nicely written article. (Link returns a 405 error but cut and pasting it works) It confirms exactly whet Peter told us a couple of days ago - at least about the rotation of the rings. Interesting that adjacent rings can dance in opposite directions too! I did believe Peter, but its good to see this article as well, and especially the bit on ring gaps as that was about to be my next line of questions for my little re-ringing project! And as for telemetry that can measure gas pressure between rings on a running engine - well my little brain cannot even begin to imagine how that is done! |
| Guy W |
| Yes got a depth bar but very difficult to get a consistent reading. The base of the oil ring groove is pretty chewed up; I've measured three ways - the depth bar and the tyre depth gauge both come out at 3.5mm, However if I measure the piston diameter (70.4) and the groove base diameter (63.1) and subtract one from t'other and halve it I get 3.65 mm. |
| David Smith |
| Sorry bout that. Try this for ease. :). http://diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php --- Edit. Huh? Still doesn't work directly. Any link experts here? Maybe this? http://tinyurl.com/gp6buxt . Yup that works. Ah, pity I didn't measure mine then David, when I had the chance, when my other engine was in bits. :(. |
| Lawrence Slater |
| Well that's a good basis for comparison then David. Guy can do the same on his TRW, and see what he gets. It only needs to show if he has a shallow groove, not be exact. It was VERY obvious, that I couldn't compress the oil rails into my 19230 pistons. That should easily show in measurement. |
| Lawrence Slater |
| My TRW pistons have an oil control ring depth of 3.49 (3.5, probably) At first I though that the depth was different on my removed #4 piston than my new unused spare. It seemed shallower until I realised that there was another spring spacer in the flat bottom of the groove that I hadn't at first spotted (or remembered, since I assembled these originally!) I also discover that the lands between the grooves are of different heights. Or at least there is a 0.05 step down from the lands between rings 1,2 &3 to the land between ring 3 and the oil control ring. Thanks for those measurements David. I wonder if your pistons have different height lands as well - that could explain the discrepancy on the diameter measures - depending on where exactly you are measuring them |
| Guy W |
| Two thoughts. 1). I'll stick my neck out. If it were me, for 36 quid and albeit potential hassle of the post and return if they aren't exactly right, -- given that you have essentially the same results as David, TRW vs OE piston with respect to the oil grooves, I'd buy a set of Grants and chance it. Worst case send them back, or, do as I did and re-use the original oil controls. To back this up, I've now done over 700 miles on my rebuilt engine, in which I've got the grants compressions and my old oil controls. Just had it up to 90 on the A21. No smoke and pulling like a hooker. 2). Equal weight (from my point of view, given that I like and have used cords before) to 1). , but cheaper -- although no return -- buy the NOS cords on Ebay. CORDS +30 here for 25 quid inc postage. NOS. 827 set, which is for OE pistons, and thus should fit the TRW's too. http://www.ebay.co.uk/itm/1275cc-MG-MINI-MARINA-1300-ALLEGRO-piston-ring-set-030-/272119886021?hash=item3f5b9bf0c5:g:i58AAOSwFMZWrNC7 Total extra cost, other than time, if you then have to rebuild because it didn't work and it smokes? An engine gasket set. Or just the head gasket if you re-use the other gaskets by disassembling carefully. But then, I love a 'gamble' when it's stacked in my favour. |
| Lawrence Slater |
| Whoops. Strike No. 2. The NOS cords on ebay have been sold to some 'guy'. ;). |
| Lawrence Slater |
| Yes Lawrence, that was me. So, thanks for the link. I had been e-mailing another seller who regularly stocks NOS cords rings and he had a +30 set but they were £40, not £25! I then exchanged a couple of questions with "your" seller before deciding to take a chance with these. I am pretty sure they will fit my pistons. The thing not yet checked is the wear on the bores, or if they are out of round - I am waiting on a set of internal gauges still. Given that there is hardly any discernible wear ridge at the top of the bores I doubt if there will be too much wear down the bore sides either. Your other option that you list - of a set of Grants for £36 doesn't seem to be available. The £36 sets from PS Autospares are County rings - I rang to check. Sussex Classic cars also have the same County supplied sets at £30 which was my close run second choice to the cords. |
| Guy W |
I have taken the mains out now. Very little wear at all on those. As its apart I will replace with new, but it probably doesn't need it. The shell surface is so even in grey colour with few scratches that its hard to tell how much wear has taken place. Similarly, the STD thrust washers don't appear to have any wear on them at all. I will check the crank end float, but they will almost certainly go back in. 80,000+ miles on those - that must say something for the concentric clutch, even with the constant contact release bearing.  |
| Guy W |
| I reckon the lack of thrust bearing wear is more about good driving techniques than anything else; not riding the clutch in traffic jams, not sitting with it in gear at traffic lights etc. |
| David Smith |
| Well it is very, very many years ago that I learnt to drive and both of those habits were standard practice in those days. Hard to break old habits, which in this case and unlike many of my bad habits, these are good ones! Which reminds me of a specific gripe I have which is about people who hold their car on the foot brake at traffic lights, dazzling the driver behind, instead of using the handbrake and keeping feet off the pedals! Grr! |
| Guy W |
| Congrat's on the purchase of cords at 25 quid inc postage Guy :). True bargain. Cords will charge you 90 quid plus for the same thing these days. "Your other option that you list - of a set of Grants for £36 doesn't seem to be available. The £36 sets from PS Autospares are County rings -- " In all the excitement then, you obviously missed my earlier post. County, supply Grants and Deeves ring sets. I'll repeat my earlier post here. ---- "PS supply COUNTY pistons. Also, looking through my hard copy of the PS catalogue -- I think COUNTY, must be a Firstline/Unipart type of operation." -----  |
| Lawrence Slater |
| Yes I did see that. But when I rang PS A and asked if they were Grants rings, the bloke who answered said no, the £36 were County rings. Maybe he was confused. Not important since I went for the cords option. |
| Guy W |
| <<Which reminds me of a specific gripe I have which is about people who hold their car on the foot brake at traffic lights, dazzling the driver behind>> Me too. Having said that, I have a Passat on loan at the moment, as my car is in for repair. It has an 'auto-hold' feature, which I also have on my own car. What this means is that when you come to a stop and take your foot off the brake, the car stays where it is until you press the accelerator. I have noticed, with this latest model, that the brake lights now stay on. |
| Dave O'Neill 2 |
| "Me too" Me too on the rear dazzlers. There are times when I might need that anger management course. lol. Don't the bastards in front realise how low we sit, and how their f*cking brake lights, and their rear fogs affect us? Selfish sods. I'd like to ram them off the road. But of course, being the laid back mild mannered understanding chap I am, I've never taken revenge by driving behind on full beam, and I've never honked my horn just to annoy them. How about the people who drive behind you with the mains on then? Or even just the dipped, blinding you in your rear view? I sometimes alter my drivers wing mirror to reflect their light back at the driver. It works sometimes too. :). Guy, that's exactly what I found. I rang, was told they were County, -- even though they had a grants number -- and then arrived to find they were Grants rings. But as you say, you got a better deal anyway. :). When are you building it? Also, it may be worth giving Cords a call re bedding in. It's a long time since I last bed in a set of cords (1998). It's not exactly the same as regular rings. Cords used to be called 'rebores in a box'. They're tighter in the bores than regular rings to begin with, and you have to be careful not to overheat. Cords sell a bedding in oil, but I never used it. Here's a link to a cords brochure, in case you don't get on in the box. www.mayphil.co.uk/creo_files/upload/files/cords_brochure.pdf Or http://tinyurl.com/hmfbo9j if the above link doesn't work. |
| Lawrence Slater |
| Cord rings arrived today. Pretty good for an e-bay purchase since I only bought them yesterday dinner time! Sets checked and all seems good and complete which is a good start! Thanks for the "brochure" link Lawrence - its more than a brochure with rather more technical detail than the little leaflet on installation that came in the box. Not sure when I will get round to fitting them - possibly this weekend. It just depends when I can get an uninterrupted few hours and a break from play-dough elephant production. |
| Guy W |
| Wow, that's amazingly quick. Superb Ebayer. I'd give him 5 star ratings and AAA+++ for value and speed of service. Glad they look fine. 1st thing to check is, put an oil control on a piston and see if it compresses easily into the bore. Assuming it will, then it's all plain sailing. :). |
| Lawrence Slater |
| Just read through that Cords brochure again myself. Fig 3 tells you how to determine the ring depth clearance.  |
| Lawrence Slater |
| Yes, saw that - that sort of detail isn't on the basic leaflet that was in the box so your link was helpful. I also spotted where that flap wheel of yours, or at least one very like it, came from! |
| Guy W |
| Yup, it's the tool suggested by Cords. I don't actually remember buying it 35 or so years ago, it may even have been supplied with the 1st set of cords I used, -- on my sisters Mk1 escort perhaps, or maybe my 1st Consul Capri before that. The dim and distant past, way too far back to be accurate about my memories ;). |
| Lawrence Slater |
| Lawrence, l am intrigued. You said earlier that you had re-ringed "dozens" of engines over the years. Accepting these may have included your cars, your sister's, your mates down the road, that is still a lot unless you were doing it commercially. It suggests 3 or more a year. What's the story behind that then? |
| Guy W |
| Over the early years is what I should have said really, starting when I was a teenager. Possibly dozens was a slight exageration, but not by much I'd guess. I had a mate whose older brother was a mechanic. He used to bring 'private' work home with him on the weekends. Simple jobs, too much to do himself, so he roped in his brother, my mate Len. Len roped me in, and we used to do it for beer money. Then word got round about how cheap we were, and Alan (the 'real' mechanic), started giving us engines to chuck new rings in, if he thought they didn't need a rebore. Some we'd strip, and it was obvious they did need a rebore, so we used to cart them off to mobile engineering in Balham (South west london near to where I lived). But those we could do, we did in the basement of my mates house. I did that, amongst other things, for a couple of years when I was a complete bum. And then continued on with my own cars, and friend's, whenever it came up. Alan was a RR apprentice trained mechanic, and I learned a lot from him. His old man was an army mechanic(ww2) and he taught Alan and Len, how to fix things anyway you could, to get going again. I added my own flavour to that lot, and use stilsons to take off rear hub nuts lol. I used to fix scooter and bike engines with my mates too. We didn't have a lot of money, so rather than rebore, re-ring. Len drove his Mini back from Hatfield Polly one weekend, with a bloody great hole in one piston. When we took it apart we were amazed that it still started, let alone made from Hatfield to Streatham. We got a 2nd hand piston from somewhere, same bore size, and complete with it's rings, we 'rebuilt' his engine. It not only ran, but ran well. My brothers mates (who were also Alan's mates) probably started all this in my head, 'reboring' their siezed bike engines with wet and dry or something, outside their houses, in the road. They smoked afterwards, but they smoked anyway, and they were skint. The thing is, of course it's way better to do everything 'properly'. But if you do, you never find out, that actually, you can make something work again pretty well, by not doing it 'properly'. You remember that old saying? They were still saying it in the late 50s and mid 60's. Make do and mend. |
| Lawrence Slater |
| Over the early years is what I should have said really, starting when I was a teenager. Possibly dozens was a slight exageration, but not by much I'd guess. lets see... lawerwnce is 88 minus 14 so thats 74 years he has been reringing pistons certianly more then a few dozen id think haha prop |
| Prop and the Blackhole Midget |
| Interesting. I was intrigued because l have worked on cars since early teens (so a good deal longer than you!) But l have only experienced doing a couple of rebore engines and never, before now, bothered with re-ringing. I did cars for family and friends and regularly bought cars to 'do up' for sale. I sort of specialised on minis and heralds of all varieties, buying abandoned MOT failures for a fiver, getting them going and using them for a couple of months before selling for a quick buck (or a few 100 or so). I used to go up to Bristol and select cars from a place that sold damaged repairables and trailer them home to work on with a friend who lived next door. Good mate he was, but sadly died a year or so ago now. But if an engine was that bad that it needed a rebote or rings it was so much easier to pick up a replacement from a scrap yard for a few quid, it just wasn't worth the time spent working on a knackered engine. |
| Guy W |
| 88 Prop? I doubt I'll get there. lol. " --buying abandoned MOT failures for a fiver, getting them going and using them for a couple of months before selling for a quick buck - " You sound like you had(have) a business head Guy. Me and Len just wanted to get beer money to get pissed. Ringing engines, as in pistons, was pretty much a dead cert' on those old cars of the 60s/70's if they were smoking and using too much oil. That's why it was so easy to buy ring sets with ridge dodgers back then. The Grants set I bought doesn't have one, but my lip is small, so I took a bit of a chance there, but only a bit. Most sets don't have them these days it seems, but the cords do because they are specifically for re-ringing engines that are worn but not kaput. Or you bought an exchange short block. But just dropping the sump and pulling the head was quicker, and the people who came to us, didn't want to spend much money. Alan had accounts with loads of car parts suppliers, and we used to get great discounts. Ring and shell sets were dirt cheap, so we always made money. When weren't doing rings, we used to service and do brakes and whatever else Alan got us. Again cheap parts, quick jobs, go and get pissed. One sunny week end we wanted to go to Gt Yarmouth, but were a bit skint. Friday night in the pub, Alan turns up and said he'd got us a Transit to change track rod ends on for an mot in the morning. Then it started raining, but we thought sod it, we'll do it anyway. Blasted down to Stockwell Motors got the bits. Midnight under a Transit, in the gutter, in the rain, outside the blokes house in Streatham Vale. Then we went home, washed and drove to Gt Yarmouth in Alan's Mk2 Zephyr 6. When we got there the sun came up and we had a great time. It wasn't all plain sailing though. One of the cars we worked on caught fire. You remember those little Honda 600 or 800's like mini e-types, revved like sewing machines? We did some work on one of those one sunny day outside the house. I can't remember exactly what, but we didn't touch the engine -- honestly ;) . The owner turned up to collect it, got in, started it up, and was sitting there chatting to Alan. Smoke, and then the bonnet began to turn brown. Whoops. fire extinguisher put the fire out, and Alan coughed up for a respray on the bonnet(or maybe even replaced the bonnet?) and new fuel lines or whatever it was. Then sometime in my mid/late 20's I grew up and got a job. LOL. But I kept on farting around with neighbours, friends, relatives and my own cars. I seem to remember even working on the local Vicar's car at one time, - and a hearse. But Alan did the cream stuff at work. We used to go out and collect cars to take back to the place he worked before he set up on his own. We picked up a few rollers on trailers. But before we put them on the trailer, we 'road tested' them. lol. |
| Lawrence Slater |
| Sorry to break in on your reverie chaps. Must admit, it also back memories for me. Like lying on my back under a J4 van in the middle of a wet night at a motorway services fitting a second hand starter. We knew the old one was on the way out so we'd got another one, but it sat in the van awaiting fitting. Sods law said it would pack up in the rain and as I was the only one in the band who knew anything about cars, they all sat in the van while I fixed it. Anyway, to business. I did a comp test on my Sprite this morning because I had been feeling that my engine didn't feel as crisp as it had been. When I rebuilt it 17,500 miles ago I was getting 200psi dry across all cylinders. This morning I got 170, 155, 165, 165 dry, and 235, 220, 215, 220 wet. I can't believe the rings have worn so much at that mileage. oil changed regularly and additive used in fuel to prevent valve recession. (Non unleaded head). Any thoughts. |
| Bernie Higginson |
| Probably not the case with you, but if you do the test without a Wide Open Throttle (WOT) then you can get some pretty random results. Otherwise, it does seem a big difference between dry and wet readings, which usually points to poor piston seals. Unless maybe you are putting too much oil in? The oil is just to improve on any poor seals. If you put too much in it lies in the piston crown, reduces the combustion chamber volume and gives you incorrectly high compression readings. |
| Guy W |
| Hope they at least got you a tea and a cheese sandwich Bernie. lol. But if those compression readings are correct, at 17500 miles, and improve when wet, I'd say the rings didn't bed in properly. In all this discussion about gaps and glazing, I read the other day about what happens when the rings don't bed in properly, because too much oil keeps the rings from going toe to toe with the bores. Substances in the oil form the glaze before the rings get a chance to cut metal off the surface of the bores, and you gradually lose compression and get increased blow by. If that is what's happened, at only 17500 miles, I'd drop the sump, pull the head, pull all 4 pistons, cover the crank, bust the glaze, rebuild and start again. The suggested method of bedding rings in, is NOT to treat the engine gently. But instead to give it plenty of open throttle, whilst making sure you don't overheat. It's not high or low revs that you are concerned with, but sufficient pressure behind the rings, to force them against the cylinder walls. And that need an open throttle, just as when you compression test. I'd not really thought about it like that before. Previously, I always driven carefully on new bores for about 500 miles before opening up a bit. But it seems that could be the exact opposite of whats needed. I'll bet it's controversial though. LOL. |
| Lawrence Slater |
| I think this may be the link I was reading from. -- Although there are similar on lots of links. http://www.ntnoa.org/enginebreakin.htm. About bikes, but applies to all 4 stroke engines. |
| Lawrence Slater |
| All tests were done at WOT. But I take what you say Guy about too much oil in there. I'll do it again next week with less oil. I don't think blow by is excessive because I'm not getting crank case pressure problems and no smoking at all. Maybe just comp rings hsve worn.I wonder if the rings I used were sub standard or they didn't bed in properly. It's overbored 40 thou and the pistons are 4 ring type which were originally supplied by the then Burton engineering on Eastern Avenue London.(Now Burton Power) when they bored and balanced it. It's been rebuilt since in 2006. I think I may do as you said Lawrence at the same time as I rebuild my T9 box, but it will have to wait till next winter. |
| Bernie Higginson |
| 170, 155, 165, 165 dry, and 235, 220, 215, 220 wet 170/235 155/220 165/215 165/220 Something is a miss... esp #2...im wonderijg if you got a broken ring maybe check the quage for accuracy |
| Prop and the Blackhole Midget |
| Lawrence. That link about bike engines seem to contradict the "Careful with that hone Eugene" article, with regard to honing. The bike one is very definite about the run times and cooling off periods. The bloody Internet is a minefield with people putting articles on telling you that their way is Gospel and forget what anyone else says. I suppose you have to read and decide which has the most credence.(Good band) :) I ran my engine in with Halford's 20/50 Classic oil for about 500 miles in the old accepted way of not labouring the engine and no sustained high revs. Then changed oil and filter and used Penrite. |
| Bernie Higginson |
| Yup bernie, the truth is what you believe, until convinced to believe something else. lol. Bernie, try the tests cold vs hot too. If the oil is sealing the rings and raising the compression, then there must be more blowby when dry, else where is the gss going? If the high readings were a result of the oil 'flat topping' the piston dishes, then the gasses may be escaping via the valve seats. Maybe even though you haven't got seat recession yet, maybe you have leaky valves. Do you have a vacuum gauge? That might give you a clue. I'm not sure if the additives you are using actually protect a 'leaded' head. They boost octane, but don't give protection. As far as I know, you need the right kind of lead for that. Are you using Tetraboost? http://www.tetraboost.com/info/ I'm trying the same experiment. I've just rebuilt my engine using my 1300GT head, but it too is still leaded. But I'm not using any fuel additives. I want to see how long it takes to show signs of leaky and recessed valves. |
| Lawrence Slater |
| <<I want to see how long it takes to show signs of leaky and recessed valves.>> Its a fair long time Lawrence. Probably depends on how you drive it but I ran 20K+ on unleaded without ever a sniff of additive, expecting the valves to recess. But they didn't even show any signs of beginning to. |
| Guy W |
| Ah thanks Guy. So if I bought a box of tetraboost, tetraethyl lead, and added that at even a quater of the rate suggested, I might be able to make my head last for way longer. But at 140 quid a box, it's actually cheaper to get hardened seats. :- |
| Lawrence Slater |
| I had a good condition standard unleaded 1275 head. I didn't see the point of getting new valve seats installed until they had worn/ recessed. So the plan was to run it regardless, and keep an eye on the seat condition until they got bad enough to replace, and only then spend money on the conversion. I checked the seats after about 5K and again after 15K and both times decided it didn't warrant any work. It would have gone longer than the 20K as well, but at that time I found an MG Metro big valve head in the local scrapyard for £5 so the experiment came to an end. The only down side might possibly have been running with a little less advance; I am not sure what it may have been happy with had I done the valve conversion. |
| Guy W |
| That was about my reasoning with my 1300gt Guy. I rebuilt the engine as cheap as poss, and didn't want to spend extra on the head, if the engine was still not up to par with the new grants rings. -- Even though I was confident it would be. I've got my advance set to book standard static, and use standard grade unleaded. Can't hear any pinking, and it's going well. Next tank I'm going to fill it with Shell V power, and see how much difference I notice. |
| Lawrence Slater |
| I got about 30,000 miles out of the original head using unleaded fuel. The valves were fairly worn when the engine was rebuilt but not bad for 171,000 miles. |
| Glenn Mallory |
| " -- not bad for 171,000 miles -- " Impressive I'd say. There's a mogie that did a million miles on it's original engine isn't there? Must have had a rebuild though. |
| Lawrence Slater |
| Looking forward to your update when you re-build your engine Guy :). L. |
| bak again |
| Never fear, I will keep you informed Mr B A Kagain, one way or another. I am waiting for a break in the rain, coinciding with daylight hours, to do some internal bore measurements. In the meantime I have been cleaning the pistons as its something I can do indoors in the dry kitchen. In particular I need to get the ring groves completely clean to make sure I get that .008" ring clearance. A broken ring makes a good scraper and then a finish off with Mr Muscle seems to work best. Norfolk? - are you in NORWICH - that well known acronym city? |
| Guy W |
This thread was discussed between 12/02/2016 and 21/02/2016
MG Midget and Sprite Technical index
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