MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Broken piston ring?

Less than a year since the engine rebuild and it's making an unwelcome noise. I hoped it was a loose rocker adjuster, but I have adjusted them to death and the noise is getting louder. It doesn't sound like small end rattle, because I've had that before and these bushes are new and correctly reamed. What worries me the most is that the noise is worse as the throttle opens. I do not understand how an essentially new engine can break a piston ring, if that's what has happened. Compressions with the engine hot and throttle wide open are 155, 165, 165, and 160. I used a proper piston ring compressor on assembly and didn't have any problems with it, just as I have done for the last 50 years or so. I'm only posting this here in the vain hope that there might be another explanation.
Les Rose

Hi Les,

You can buy fairly decent and affordable endoscopes on Amazon which will allow you to look into the chambers through the spark plug holes.

https://www.amazon.co.uk/Inspection-Depstech-Waterproof-Borescope-Smartphone-Black/dp/B01NBFTAHE/ref=sr_1_13_sspa?crid=SH1Q9MU26AFJ&keywords=endoscope+inspection+camera&qid=1695800600&sprefix=Endo%2Caps%2C111&sr=8-13-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9tdGY&psc=1

I would imagine that if one of the rings had broken you’d see some scoring on the walls.

Worth a try before pulling the head or removing the engine.

I used mine to find out why it was burning oil.

Did you fit your new radiator? Could it be related to that?



James Paul

"What worries me the most is that the noise is worse as the throttle opens."

A blowing exhaust manifold can make a racket, perhaps even the head gasket?

What were your compression readings immediately after rebuild?

How many miles on it now? Is it run in? What engine?



anamnesis

Yes I have an endoscope. I'll have a look with that. I'll check the manifold gasket but the sound is more of a mechanical ticking. I didn't think it was useful to test compressions before the rings had bedded in.

The radiator is a longer story. MCCS was hopeless, they have none in stock and won't answer phone or emails now. I have one coming from SC Parts tomorrow, assuming UPS can get their finger out.
Les Rose

I'm with Anam on this. A blowing exhaust manifold can make a VERY metallic sounding clack clack noise and worse under load and when warmed up. I've had that and was absolutely convinced myself it was a little end bearing. far easier to check that before dismantling anything. They tend to blow on the underside where you cannot see!
GuyW

Head gasket leaking between cylinders can too, though compression readings indicate this is unlikely. Jet of hot stuff through the leak ignites the neighbour on compression stroke.

At the gloomy end, another explanation can be excessive piston clearance due to piston picking up on the bore as a result of inadequate clearance or being too hot. Have an MGA twincam in the workshop with exactly that after a full recond (elsewhere, whew), piston wore 10+ thou as result an gave a very harsh bearing-like knock. (bearings are all mint). Again, this would show up on compression readings so not likely here. Marking were visible in the bore.
Paul Walbran

Yep you remind me that I've got piston slap too Paul.

Started after the block was bored to 30 thou, and installed 3 ring 19320 hepolite pistons. Fantastic compression, but makes a noise. Nevertheless, that engine did over 100k miles and went very well until the ends wore, low oil pressure. Sat under my bench for years as a spare. Then I had the crank ground, and stuck another set of rings on the same old pistons a couple of years ago, and it's done another 10/15k miles. Still great compression, still slaps. But I don't 'think' it gets worse on opening throttle, and gets a little quieter when fully hot. I'll pay more attention to it next time I use it after I come bavk from holiday.
anamnesis

Thanks chaps, I am going to fit a new manifold gasket when it arrives. Just took the old one off. It didn't look too bad, but worth a try.

Meanwhile back to the radiator saga. Having sent back the Chinese one for a refund, as there was no car on the planet to which it could be fitted, I went to a reputable company for another one. It turns out the one I got from SC Parts, which they sent from Germany, is also Chinese and doesn't fit. So that's going back as well. Worse still, they charged me £125 more than the previous one. What is going on in Chinese factories? I thought that in the Far East they were good at copying things.
Les Rose

Bad luck Les

I have found SC Parts a little lacking in the past, they seem to do little checking when sourcing parts. A head for healeys has been better for me.
Bob Beaumont

Les
Is it worth trying a re-core of your existing vertical flow rad? It's worked before so maybe is just limescaled up from hard water?
Bill Bretherton

WARNING-Thread drift
Paul W
With the Twincam- Just out of interest did it have new pistons-
Did one here last year and had pistons made for it and they were forged and had to run a fair whack of clearance-.004" from memory
I'm wondering if your engine has a set of these as well and the reco mob went from the workshop book and didn't allow enough for expansion.
Crazy engine with everything spinning backwards, took me a bit to get my head around cam timing following the book, but once you sit back and think about it, it all falls into place.
Plenty of dodgey parts available for them, keep your eyes open - there are some chain guides floating about with aluminium rivets holding the pads to the brackets that are prone to shearing the rivets---the rivets need changing to steel ones if you're replacing the guides
One thing that does get missed in recoing them is if it's someone that han't done one before is the spacer for the oilpump drive shaft---I'd be checking to make sure that's there and not sitting on someone's bench.

willy
William Revit

Maybe I have found what was causing the ticking noise. A few months ago I bought a new LCB from Maniflow, and from careful measurement it appears that the flanges were very slightly thicker than on the old one. This reduced the clamping force on the inlet. I have made spacers for the inlet to get all the flanges exactly the same, according to my vernier gauge. This is all a bit fiddly because this MG Metro inlet had to be chamfered to reduce the angle and get the carb under the bonnet. Of course, from what I have found it would be air leaking into the inlet rather than exhaust gas leaking out, and I'm doubtful that would make the noise I was hearing, but we shall see.

I can't of course test this because the radiator is out of the car now. Yes Bill, of course I can get it recored but there is nobody locally who does that any more. I would very much prefer to uprate the radiator as on track days it always used to get pretty hot. There seems to be little option but to pay £500 for a British made aluminium one. I am really quite appalled that when I ask some suppliers where their radiators are made they actually don't know. Now I'm stuck with the car off the road and most likely have to put the old radiator back in for the time being.
Les Rose

Willy, the pistons were apparently in good order and re-used, with bores sleeved to match. Re-used because they were high compression and the owner had trouble finding replacements and wanted to retain 9.9:1.
Bored to 4 though clearance. Book spec is 3.5-6.5, so that was the lower end of it. Leaving the block to thermosyphon along with a large area on the piston dome results in quite a bit of expansion. Add mixture or timing not quite right and 4 thou obviously wasn't enough.
Given the knock I didn't want to run it so haven't diagnosed further at this stage. However we will be recording the static ign timing before disturbing the distributor then check the advance curve and AFR once back together.
Paul Walbran

Back to Les'radiator, we had one arrive like that a few years back, so they have been around for a while. A bit harder for us to send back.
Ultimately we did, along with a crate of other (new) crap. Freight cost was about 1kGBP but there was enough in it to make it worth it.
So many poor parts....
Paul Walbran

Hi Les,

Did you see my post about the radiator?

I've spoken to Arrow in Bristol and they said if you post it to them they'll upgrade it and post it back within the week. Shouldn't be more than £10 using a courier.

Failing that they said to try Rayson's in Yeovil who might be able to collect it and return it.

https://raysons.co.uk/#repairworkshop
James Paul

Les, I had the same problem when I put a Maniflow LCB onto the engine with a wedged Howley racing inlet manifold. My solution was to cut some suitably sized stainless steel washers in half and stick them to the large washers (1 per washer) with double sided sticky tape. That was 4 years ago and I've had the engine out about 3 times in that time (for gearbox problems) and they are still stuck down to the big washers. I thought it would be temporary but so far it's been permanent.
Rob
MG Moneypit

Thanks James. I'll try to order an ally one from MCCS tomorrow, if I can get them to communicate. Failing that, I'll have to go for a recore but having the car laid up for a week is a pain.
Les Rose

If you maniflow is like mine it is one continuous piece of kit until a join under the car. This makes everything quite rigid and I found I had to slacken the mounting under the car when I refitted the manifold to get a good seal to the head.

Jan T
J Targosz

Yes Jan, I always loosen the clamp under the car, or the manifold can't be disconnected from the head. I have started the engine and there was no ticking, but that was only for a minute or so.
Les Rose

Bad news. Went for a short run today. Ticking noise just the same. I could not see anything clearly with the endoscope. Might take rockers off tomorrow and put the spare set on, but I'm not hopeful. I have not broken a piston ring since 1968.
Les Rose

Another thought. What about a broken cam follower? As they are designed to rotate, that would explain the noise coming and going. They are good quality ones from Mini Spares, installed with cam lube of course. Today while I've got the rockers off I'll pull out the followers. Thank goodness I have an early block with side covers.
Les Rose

Les

I had cam followers fail after 2000 miles, they were not rotating. The cause was due to them being incorrectly ground which I gather from Swiftune is a common problem. They came from Mini Spares, I sent them back but never heard from them. I bought a replacement set from Swiftune and have had no further worries.
I have a set of genuine NOS BMC ones if your stuck!

Bob
Bob Beaumont

Have you tried a stethoscope? Useless for whirring noises but great for knocks and taps.

Jan
J Targosz

B series problem that makes that sort of noise is rocker shaft resonating in the posts. Factory fix well into production was 2 x 5 thou shims under the centre two posts. (it works) I haven't come across it on A series but who knows...
Paul Walbran

I initially thought about rockers, or specifically wear of the rockershaft and/or bushes but in his first post Les stipulates that the noise increases with throttle opening.
So it seemed unlikely on second thoughts.
But...
No amount of tappet adjuster twiddling will silence a worn rockershaft and it's such an easy thing to check so I'd do it anyway, just to positively eliminate it from enquiries.

(I know beyond doubt that my rockers and shaft are worn and a bit noisy but I still haven't got round to replacing them. No excuses for this - it's a dead simple job on a 1500).
Greybeard

I took the rockers off yesterday and found one had a worn tip - see photo. I had reprofiled them on the lathe, but the case hardening must be thin and this one broke through. I put the spare set back on. These are pressed steel ones with welded tops, and have good tips and bushes. The shaft is fairly new, and there is no detectable play when rockers are fitted to it. The forged rockers I just took off had newly reamed bushes anyway. So I thought I had found the problem.

But no, I warmed up the engine on a short run today and the noise was exactly the same. I will now pull out the cam followers - one thing at a time.



Les Rose

Les
When exactly do you hear this noise--what revs throttle on/off etc under load/free reving/overrun etc and does it do it at all temps.
Something that's caught my attention, -how do you reface rockers in a lathe-?

willy
William Revit

The pistons are out now. All the rings are OK. Here is what the big end shells look like. They have only done 3,000 miles. The cam followers are fine.

I only get the noise when warmed up. It is present from idle onwards.

I refaced the rockers by cobbling up a jig on the lathe carriage using an old shaft fixed vertically, and using an unworn section. The rocker was sprung so that it was held against a grinding stone in the chuck. As the carriage was moved against the chuck the rocker rotated so that the pad on the tip was always tangent to the stone.

I simply don't know what else I can do. I think I will just replace the big end shells and put it all back together. I will also consider using a different oil. I have never in the past had any problems with bog standard 20-50.



Les Rose

...and here is one of the cam followers. A bit scuffed no worse than I have seen often before.


Les Rose

My followers wore out on the mating surface between the cam and follower. There was a distinct stripe on the face of the follower caused by the camshaft
Bob Beaumont

Them bearings look like they've been to war. Either starving for oil pressure or wrong grade oil.
Do the shells in the rods look the same as that or worse-?
Does it have a mechanical petrol pump that's failed poking fuel into the oil
What oil/grade are you using--not synthetic by any chance

Thanks for the info on the rockers--I've been churning over in my head how you could spin the rocker in a lathe to get the arc correct--but yeah you were just using the lathe as a pedestal grinder-

On the bearing issue--I had a 6cyl Falcon turbo in one day that the guy said rattled when hot-it was on synthetic 0/40 - You could take it out the road for a fang and it'd be fine, but if you went again with a bit of heat soak and gave it heaps it'd get a little rattle, didn't sound like bearings but would do it in neutral with a bit of throttle off idle-more like a piston rattle-only sounded like one cylinder rattling--unhooked the injectors one at a time and tracked it to No2 cyl-----Just for a try, drained the oil while it was hot and put fresh in and the noise disappeared until the oil got hot again
When the engine came apart everything looked fine except no2 journal was .00025" smaller than the others--poked a new crank and shells in it and all was good-----synthetic--very reliant on good bearing clearances

And----Bob is correct, it would be the end surface of the follower that would make a clunking noise ,what do the ends of them look like

Just trying to remember--I used to do a bit to an old side valve v8 racer a few years back, it was a good reliable old jigger and always ran 50psi oil p. but the owner wanted to try synthetic oil in it. It used to run on 20/40 mineral oil so we went for 15/50 synthetic---All good for about 10 mins on the road till the oil got hot the 10psi.max---the clearances are just too big in these older engines for synthetic oils

willy
William Revit

Thanks Willy

The shells in the rods look the same, see photo. Oil pressure is over 50 psi hot. As I said before, I use standard 20-50 classic oil, which has always served me well over decades. I would never use synthetic oil in a classic engine. The fuel pump is electric.

The cam followers are not worn on their faces.

New bearing shells are going in, and I will spend a lot more money on oil. Options seem to be Dynolite or Penrite. What do you guys use?

Of course, without pulling out the engine I can't change the mains, but they are likely to rumble rather than rattle.



Les Rose

Another thought. I like my lightened forged rockers, so I'll reface them again and try re-doing the case hardening. There is stuff available to get the carbon into the steel. I recall my dad had a little tin of sticky greasy-looking stuff that he said was for case hardening. That was in the 1950s. I've seen lately there's a product called Cherry Red, which presumably means how hot you have to get the work piece.

I'm just rambling. Ignore me.
Les Rose

Les,

Kasenit , I have a rusty can of it that my neighbour gave me as he didn't want it any more. Various discussions and recipes for it online. Apparently the active ingredient is sodium ferrocyanide and/or potassium ferrocyanide, the latter being available on ebay. I think in order to get a good depth of case just on the pad you'd have to mask the rest of the rocker arm, is the rest of the rocker hard or just the pad. I found out not that long ago why the inside of Cox glow plug engine pistons were copper plated, it was so the case hardening process didn't effect those parts of the piston so they remained malleable.

Stellite the pads?
David Billington

I use Castrol 20/50 and have had no problems
Bob Beaumont

I think I now know what has been going on. The radiator could not cope with the hot summer, the gauge reading 95ºC at cruising speeds. The oil film broke down and caused the bearings to pick up. A better oil might have prevented that. The good news is that all this can be fixed with a set of bearing shells, some new gaskets, and a refill with some decent oil.

Yes Dave, I read about Kasenit. It also contains charcoal, as both carbon and nitrogen are needed. Hardening the rockers may be tricky, as they have new bronze bushes and I'd have to avoid damaging them with heat. I would not want to press out the bushes, as it's more work and re-using them isn't ideal. New bushes would have to be reamed and that takes ages. I wonder if a propane torch would get just the tip cherry red without the rest getting too hot? The other issue is that commercial case hardening takes hours in a furnace, in at least two stages. I suspect the rocker would cool too quickly to get much penetration. More rambling!
Les Rose

Dave, I forgot to ask, is Stellite treatment feasible for the amateur?
Les Rose

Les,

I threw that in at the end of the post as I remembered I have 1kg of Stellite 12 for TIG or OA application. Likely somewhat over the top and I've not tried it before but a quick look online shows others with the same issue of needing to reface rocker pads or similar so some more research required. The guy at Deloro Stellite in Swindon mentioned that it would be hard on ordinary wheels and that they used diamond IIRC. At Swindon they did the 4m knives for shearing the pile on Axminster and/or Wilton carpets amongst other things. The only pads I've re-profiled and hardened were on pressed steel rockers and all went well.
David Billington

New big ends fitted, and engine filled with Castrol XL. Ticking noise has gone away. Only a very short run so far, but looking hopeful. Old radiator back in, while I search for a cooling upgrade of some sort.
Les Rose

Les--just as a precaution---ignition timing
Paul Walbran touched on it earlier talking about the T/C MGA.
Overadvanced dist.timing can kill bigend bearings-
It might pay to check your distributor to make sure it isn't advancing up too quickly/far--just to be sure to be sure-----might have something like a broken advance spring that'd throw it out of spec.
willy

edit--just noticed on your overheating posts that you've had the dist. checked
But I'd trust noone and check it yourself with a timing light and see what it's doing--i'd think 10deg idle would be a good starting point and see what it does from there.
William Revit

Willy - it is 7º at idle. The curve now has less advance at high revs than it did before, so I'm told by H&H Ignition that set it up. I don't think it's a problem, but thanks.
Les Rose

The ticking noise is back. Not quite the same this time. It doesn't seem to depend on throttle opening, and it comes and goes seemingly at random. As before, it sounds like a loose tappet, but the rockers are different and I have adjusted them twice. I remember about 35 years ago we had a Mk 2 Escort with a very similar noise. I stripped the engine and found nothing wrong with it. Put it all back together and it made the same noise. An old chap who ran the garage around the corner told me to idle the engine with the rocker cover off, and put a feeler gauge between rocker and valve, one by one until the noise stopped. Suddenly I knew which one was too loose. I could not adjust it with a feeler gauge because of wear on the rocker tip. I can't remember how I got it right now. I probably just closed it up bit by bit until it seemed about right. What I don't understand is that with a different set of rockers I get the same noise. I don't think it's the small ends, because the bushes were new and freshly reamed. None of them seemed loose when I had the pistons out. I don't think I can face crawling under the sump again and getting the pistons out, and having checked everything there and renewed the bearings I can't imagine there's anything wrong. But something is.
Les Rose

Coming and going and sounding like a tappet --sort of points towards a cam follower with a wear mark, and rotating around into differently worn spots
Bit hard to tell without hearing it though really but I think that's probably the most likely
Were they new when you reco'd the engine--
William Revit

Yes Willy, of course the cam followers were new when I rebuilt the engine. As I showed in a photo earlier, they were a bit scuffed on the sides but the faces were fine. I am also wondering about an oil feed problem. I'll order a new set of followers and check the oil passages in the rocker shaft and rockers. Does anyone have recommendations for good quality followers?
Les Rose

Les

I got mine from Swiftune as I had problems with the minispares ones. They were not the cheapest but I have a 1275 so replacing followers is an engine out and strip!
Bob Beaumont

Also well worth plugging the upper oil holes in the rocker shaft to maximise feed to the lower contact regions.
This was a typical mod carried out on Minis back in the day !
I covered this aspect in Mascot a couple of years ago in May 2019.
Upgrading to an increased wall thickness shaft to enhance stiffness is also applicable but make sure it is not full of swarf like those supplied to me by Mini spares !!!
S G KEIL

Good tip about the rocker shaft holes. It was a new one not too long ago and was advertised as uprated for competition, but I can't remember where I got it.
Les Rose

New cam followers and rocker shaft fitted. Manifold taken off and checked back at Maniflow - no sign of cracks. Noise is exactly the same. Louder when throttle opened under load. My race engineer friend suggests sparking from faulty plug lead. With bonnet up and idling it still sounds like tappet noise. Will try new plugs and leads.
Les Rose

Les,

Has it always knocked or did it start some time after the rebuild. I ask as I'm reminded of someone I used to know that bought a car with a newly rebuilt engine that knocked and it was eventually traced to one piston being the wrong size, how that was resolved I don't know as the pistons were only sold in sets of 4.

Have you tried running the engine at night and so you may be able to see any HT tracking.
David Billington

Trying to think out of the box--
You don't suppose it has a crack in the fan belt-they can make some weird noises
Maybe warm it up or whatever you have to do to get it to make the noise then take the belt off for a try

willy
William Revit

Probably unlikely unless you have high lift rockers but you might check the inside of the rocker box for marks or scraping. And of course a worn timing chain or gears can rattle without a tensioner.
f pollock

New plugs are in. As usual I could not get the right ones, the nearest I could get was NGK BR9ES. The noise is less, and is more intermittent. This suggests it is ignition related. Tried idling engine in the dark, no sign of sparking. I'll try HT leads next. As usual (again) you can't buy these by the length, have to order online.

No Dave the ticking only started about 2 months ago. And I've just had the pistons out again. Can't find anything wrong mechanically.
Les Rose

You said, "This suggests it is ignition related--".

Try retarding it a tad.
anamnesis

Might running it with each plug lead disconnected (in sequence) enable you to identify if the ticking noise is related to one particular cylinder?
GuyW

Guy said "Try retarding it a tad.".

I did. Noise still there. After the rebuild a year ago I optimised the timing at idle to 7º BTDC, and it ran like that perfectly well until a couple of months ago. If it is detonation then it would depend on a hot spot. I had the head off recently as you know and could not find anything wrong with the chambers or pistons, and I now have new plugs. Interesting idea to try disconnecting plug leads one by one but I would have to drive the car on the road as the noise depends on throttle and load.
Les Rose

Still getting nowhere. To recap:

Since the noise started, I have replaced:

Big end shells
Cam followers
Rocker shaft
Plugs
Distributor cap
Plug leads

I swapped the rockers for a spare set. Checked pushrods - all perfectly straight and undamaged. When the engine was rebuilt a year ago I fitted and reamed new small end and rocker bushes. I tried using a screwdriver as a stethoscope, which might have told me if the noise was coming from something in the block, but it didn't. As I have said, it still sounds to me like a loose rocker, and others who have heard it say the same. But I don't understand how the amplitude of the noise can be related to throttle opening and engine load. It doesn't seem to me to be typical of small end rattle. I have had that before and it's not so linear in the way it sounds. Loose small ends concentrate the noise around the mid range and at part throttle, whereas what I am getting is a steady increase in loudness as the throttle opens, and as the engine gets hotter. The engine of course runs much cooler with the new aluminium radiator, so detonation is even less of a risk.

I really can't think of anything else I can eliminate from this saga. One day whatever it is will break and then I'll find out.
Les Rose

I forgot to mention a couple of recent things.

Way back, I optimised the rocker geometry by machining the pedestals and shimming appropriately. This was to get the maximum lift. It does make the rocker angled up a bit with the valve closed, the idea being to have the pad move equally up and down. With the valve closed this can make it difficult to set the clearance accurately because the rocker pad moves further back across the tip of the valve. This is a result of the pivot of the rocker being way below the line between the valve end and the push rod end. Anyway, I tested this by trying different shims, finishing up back at standard height. None of this made any difference. Actually I don't think this exercise really optimises the geometry because of the aforementioned mismatch between pivot point and the points where the loads are acting. It might be more important for very high lift cams.

Being puzzled by the noise getting louder when hot, I checked the valve clearances hot. They were all tighter, as you would expect. Something else is expanding and creating a wider gap.
Les Rose

Les,

I would question the reaming of the small end bushes as the engine machinist I used would do almost all the processes in house except the small end bushes, those were done by a local honing specialist due to the tight tolerance required.
David Billington

Interesting point Dave. I have reamed new small end bushes before, with good results. The ones in the old engine I did over 10 years ago and they are still good. Should I take the rods out of that and put them in the new engine? Possibly not, as it might change the piston heights which I had carefully set.
Les Rose

Les,

How did you guide the reamer to achieve the correct alignment of the small end bore to the big end?
David Billington

By hand Dave - it's a hand reamer. I thought it was supposed to be self aligning.
Les Rose

Les,

A hand reamer can't be relied upon to accurately follow the bush bore on its own so that may be your issue with one or more pistons crooked on the rod but it's not something I've ever come across so not sure what symptoms it causes. While you were dealing with the rods did you check the big ends for size and ovality.
David Billington

No I didn't check the rods, I've never had any problems with them before so it didn't occur to me. They are coming out again now so I can do it then. I must have been lucky with the hand reamer on the other engine.
Les Rose

I know this is getting boring but a few of you might be still interested. I'm about to get the rods out again, and had to search around for somebody to hone the new bushes. I was directed to local company Formhalls that specialises in classic and vintage cars. They advertise all types of machining work, and last year I got them to quote for the engine rebuild. They were outrageously expensive, but I thought I'd give them a try. They wanted £600 + VAT. I can buy a new rod for £60 + VAT. Somebody else directed me to a company called believe it or not Southern Gun Drilling. Yes they drill gun barrels. They are doing all 4 for £80 cash. I have made it clear they have to hone these in line, and they seem to be familiar with that sort of stuff. They can't do the job until Wednesday, so I have plenty of time to get the rods out and press in the new bushes.

If the engine still ticks after all this then I have totally run out of ideas.
Les Rose

Will you get a chance to check the camshaft bearings?
Greybeard

Leave it alone. Let it it be. Let it knock.

I've had a 'knock' in my 1275 engine, which I hear far more in the winter but also when cold in the summer, for more years than I can remember.

It was there from when I first built the engine in the 80's. It did well over 100k miles. I rebuilt it again not so long ago. Crank grind, new shells, but just bunged new rings on the same pistons. SAME small ends as from the 80's.

It's done circa 13k miles since rebuild. SAME knock. But the engine is strong, and with cooper s pistons, 1300gt head for what it is, it goes very well enough.

In short, if it goes well, forget the knock. Leave it alone.



anamnesis

I bit the bullet and pulled out the pistons again. One rod small end was a bit loose, another very slightly. The rods are at the gun driller now and I'll pick them up on Thursday.

I won't bother with checking cam bearings as they were new last year, and I have found another source of the noise.
Les Rose

Les- the gundriller sounds interesting, the machine shop i use here has a milling machine and uses a small fly cutter for machining rod bushes, bit like a boring bar I guess. I had some axles gun drilled years ago, not cheap, but it did the job.

"and I have found another source of the noise." sounds interesting.
William Revit

Willy,

The company Les mentioned Southern Gun Drilling https://www.drillandhone.co.uk/ do honing as well as gundrilling so even if the small end bushes were bored to remove the bulk of the material I would expect them to be honed to final size. I expect Les will report back soon and hopefully all is well again just the weather is not ideal at the moment with a bit of a cold snap here apparently improving early next week in these parts.
David Billington

All back together now and I just went out to warm up the engine and retighten the head nuts. When cold there is absolutely no ticking at all, and just the usual tappet noise when hot. So problem solved at last. My goodness it took a hell of a time to warm up in this weather. The finish on the honed bushes is excellent of course, and the fit perfect.

To summarise, I was misled because reaming bushes myself worked fine a few years ago, with those rods still in the spare engine and not a sound from them. I was just lucky, and didn't get away with it the second time.

Nearly forgot to say, when I started the engine up it initially ran rough. Found it was misfiring on one cylinder. After a few hours of frustrating analysis, I took out the brand new plugs and put the very old ones back in. Runs perfectly now.
Les Rose

Les,
You are not alone with issues when reaming.
As you may know I play about in my workshop and think reaming is still a rather difficult thing to get right-
Reamers seem to have a Will of their own and will dig in at the least opportunity especially when dealing with sticky metals such as brass/bronzes.
Even with my pretty accurate model/ clock type lathe I have had inaccurate results at times - often better just to bore with a sharp tool !

Free Hand reaming (spiral flutes) to high degree of accuracy is not something I would attempt these days - fortunately steam engines generally are more forgiving in tolerances !!

Glad you’ve got it sorted and very well done to keep at it - especially with the cold temperatures recently!

R.
richard b

congratulations Les!
Flip Brühl

Hi Les.

As Willy remarked earlier. You said,

" -- and I have found another source of the noise."

Was that a red herring? Or did you find an additional noise nothing to do with the small ends?


anamnesis

Persistence, Les. Well done!
GuyW

I didn't mean there was another source of noise than the small ends. I should have said I had found the real source. I was also misled by the noise itself. It didn't sound like small ends, which I have heard before. Others who heard it said it was a rocker. One is never too old to learn.
Les Rose

Ah right. Thanks.

Interesting saga, even if it was an expensive frustrating pain in the proverbial for you though.

anamnesis

This thread was discussed between 26/09/2023 and 03/12/2023

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.