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MG Midget and Sprite Technical Oil pressure feed and relief. BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - Oil pressure feed and relief.
| As a spin off, no pun, from the engine breather/oil sucking thread, I thought I'd post this. One of the factors considered in oil sucking, is high oil pressure, being a cause of over supply to the timing chain cover. Notwithstanding that a number of oil sucking engines have normal oil pressure, it's also a fact that some have high oil pressure, as do my oil sucking engines. So even though I'm sure oil pressure isn't the cause of oil sucking, I thought I'd take a closer look at exactly how the pressure is supposed to be relieved, when it is too high. I double checked my spare engine for blockages along the gallery with air, and found none. I also checked that the relief valve piston was free to move, which it is. Here's a picture of the route the oil takes from the pump, both to the feed to the oil filter, and the feed to the pressure relief valve. And here's a link to a video I took, of my pressure relief valve bobing up and down to the pressure of my breath. -------- http://tinyurl.com/q62bohg It's free to move, and the spring is the correct length. So how is my pressure so high? If the relief valve was getting stuck, it's hard to see how. Oil pushes directly on the base of the piston, not on the side. The oil pressure gauge reads pressure at the end of the oil gallery, not nearest the filter. I tested 3 different oil pressure gauges on this spare engine before I stripped it. When turning the crank by hand, all read the same. Are they ALL reading too high? It's a mystery.  |
| Lawrence Slater |
| Mmmm, Perhaps you should have drank the coke a cola and used the pepsi instead Prop |
| Prop and the Blackhole Midget |
| Nah. I should have snorted the coke. lol. Here's my spring. If anything it's a tad short, so the pressure should blow off earlier than the quoted figure. Which according to the BMC manual, is actually only 50lbft for a 1275, not the often mentioned 60/65.  |
| Lawrence Slater |
| How to relieve high oil pressures ? Well 1st id ask ... what is considard as a high oil pressure and under what conditions 10 psi per 1000 rpm is a general rule, but there exceptions like all rules Im running 80psi on tick over but once eated up.it.falls down to around 30 psi at idel, maybe a bit high, but then agian ive got a new engine so its to be expected Im sure once I get a few X000 miles it will fall off a bit more On my work truck ive got 240,000 miles on the clock, ive recently started using 20/50 oil instead of 15/30 the hand book says and that has given a nice bump to my oil pressure to optimal specs I dont think there will be a one size fits oil pressure Prop |
| Prop and the Blackhole Midget |
Whoops. Forgot picture of the spring.
 |
| Lawrence Slater |
| When I built my engine I used the adjustable thumb screw spring and ball bearing but still there was an issue and I had to modify the spring to fit properly I want to say I used the old spring with the new ball bearing and the adjustable thumb screw cap to make it work correctly Snorting is so vintage...haha Prop |
| Prop and the Blackhole Midget |
| 72mm free length is correct and I think 50 lbs/sq.in is the pressure at which the valve will begin to move off it's seat. With a typical 20/50 weight oil the gallery pressure will run between 40 - 70lbs/sq.in with a 20 lbs/sq.in hot idle. |
| Fergus Pollock |
| Hi Fergus. My spring is actually just under 72mm, and the book says 72.63mm. I doubt such a very small difference in the free spring length makes any difference to the oil pressure valve lift though. So to all intentents and purposes as you say mine is 72mm. But my oil pressure on this spare engine, and on my current Sprite engine, which also has a 72mm spring in it, reaches circa 90 on cold start, is 60+ on idle when hot, and cruises at circa 75/80 psi. Even if I had a super dooper oil pump, which I don't, I have the original factory standard types in both, the oil pressure shouldn't get to those levels. And yet it does. |
| Lawrence Slater |
| Hi Lawrence, My oil pressures are pretty much the same as yours and possibly a tad higher with no perceivable ill effects. it's a 1330 and is well and truly thrashed. |
| G Lazarus |
| Hi Garry. I agree, no ill effects. I'm just curious how it can get to those levels if the relief valve is working ok. |
| Lawrence Slater |
| The A-series engine lubrication system is designed around getting a certain VOLUME of oil through the engine across the rev range. As long as you have that oft quoted 10psi/1,000rpm you can be assured the engine has enough oil moving through the critical places to carry away the heat. It's all about the VOLUME - not the pressure. Anything over the 10psi/1,000 rpm is actually costing you horsepower through shafted friction, and generating additional heat along the way. When the 1275 midget prototype arrived down under in 1966, it was soon discovered that the oil was getting way too hot in the summer here, and a 10 row oil cooler was fitted as standard equipment when the cars went into production in late 67. The 1275 Cooper S needed a 13 row as standard equipment in Australia. Around 85% of the cooling in a a-series 1275 engine is carried out by the oil - not the water. Tony Slattery Black Mountain Australia |
| A L SLATTERY |
| Lawrence I'm sure you know this better than I, but it is not just a measure of spring length and/or number of coils, but the spring rate (inch per lbf or cm per N) that sets the relief pressure. I don't know what it should be, but someone out there surely has a figure so that it can be checked by applying a force and measuring the compression of the spring. I haven't checked my spring but oil pressure never exceeds 60psi. So, according to Tony, I shouldn't exceed 6000rpm, then! (But I still do....) |
| Peter Blockley |
| Cheers Tony. I'm not at all worried about not getting enough oil through the engine. What I am, is curious as to how the oil pressure can exceed the suppposed blow off from the pressure relief valve. Of course I can't be absolutely sure that all of my oil pressure gauges are reading correctly. But it seems unlikely that they would ALL give the SAME WRONG high reading. So assuming that they are broadly correct, how can my oil pressure be higher the than the relief valve is supposed to let it get? The spring is the correct length. It's the original in the engine, ALL 3 of them are as far as I know. (Spare engine, Sprite engine, and Midget engine, all 1275). Can the spring be the correct length and be too stiff? Can anyone suggest a means to measure it's strength, --- without having a pucker spring measurement machine? |
| Lawrence Slater |
| Cheers Peter. So how can I check the spring rate, -- with simple garage/home tools and equipment? |
| Lawrence Slater |
| I have heard it said that too high an oil pressure can rupture the oil filter cannister. |
| Graeme Williams |
| Hi graeme. It shouldn't. There's a filter bi-pass for when the filtter is blocked. This does mean though, that you get unfiltered oil pumped to the oil gallery, and hence the rest of the engine. |
| Lawrence Slater |
| Lawrence, Its the lift off pressure that is noted i.e starts to relieve at 50lbs. So the spring length/ strength/packing washers is only there to achieve that - I'm sorry if that sounds obvious ! With steam engine boilers (models in my case) we need blow off at a specific pressure and build blow off valves that can be adjusted against a known accurate gauge. So can you rig up some air/water pressure such that you can incrementally increase pressure until you reach a point of leakage - will need a bit of blocking/bodging connections etc - your existing gauge will probably give a good enough reading.Even a bike pump can be used. As to why pressure still exceeds the blow off - it has to be as Tony noted 'volume' of oil produced at pressure, that is more than can be dumped via the available waste return hole. As the oil thins the flow increases and max pressure drops back to 70 ish. I seem to also remember from my experiences that early 1275 ran slightly lower hot max pressures than from about the change to the facelifted ones - not sure if this is related to oil pump changes that occurred - not seen this noted anywhere though. My longest post ever ! |
| richard boobier |
| Maybe you've got packing washers jammed inside the nut,effectively increasing spring rate. The spring should have a fitted length of 54mm with 13 to 14lb load. |
| Fergus Pollock |
| Lawrence: if the filter isnt blocked, it would be subjected to the running oil pressure which could, from all accounts, be 90psi+ Spring rates: Quick check on a new sping gave 11 lbs causing a 15mm compression, (and 5 1/2 gave just over 7mm). Not precise but "ballcourt". If you know the area of the relief plunger and a few measurements to give the distance the plunger has to move and compress the spring... and the spring's initial compressed length, you should be able to work out the pressure needed to hit the releif gallery! |
| Graeme Williams |
| Yup it would be that high Graeme. Mine can touch just under 100 in the really cold weather (gauge accuracy dependant). But I've never seen an oil filter in a Spridget, blown apart/punctured by high oil pressure. Did you just rest the weight on the upright spring then? Ok simple enough, I should have thought of that. Doh. I'll have a go tomorrow. No definitely nothing in the nut Fergus. And I checked on my spare block today. The depth of the seat, means that when the nut is tight, the spring must the compressed length you quoted. I also pulled the spring and plunger from my Sprite engine. Came out easily, no sticking. AND the chamber had plenty of oil in it. In order for that to get there, the plunger has to have been lifting, and the oil residue that didn't drain off, was still there. Clean fresh oil. Well at least as clean and fresh as there is in the sump at the moment. Ok, got it Richard. That suggests, that inspite of what I think, I could have a high capacity/volume pump on the engine, which the relief valve can't keep up with. I don't recall ever buying one. That last time I bought an oil pump for the Sprite, was back in the 80's. They just don't seem to wear out, so I re-used it again and again. The spare engine pump should be the same as far as I know, so I'll look at that tomorrow and see if it's the standard pump that I'm sure it is. |
| Lawrence Slater |
| http://www.somerfordmini.co.uk/eshop/index.php?main_page=page&id=119 "It used to be the case, back in the 1960s, that if you wanted a high capacity oil pump you would fit the Cooper S item (note that high capacity does not mean high pressure; it simply means that more oil is pumped around the engine - oil pressure is of course controlled by the oil pressure relief valve). However from 1968 all oil pumps excluding that fitted to the MG Metro Turbo and ERA Mini Turbo, but including replacements for the earlier 1960s types, have been of Cooper S capacity. As a result, if you want a high capacity oil pump today, you can fit the GLP110 Metro/Mini Turbo item. " So according to that, I've got standard capacity, and anyway, it doesn't raise the pressure. |
| Lawrence Slater |
| And just for interest. http://www.calverst.com/articles/Eng-Lubrication-Oil_pumps.htm |
| Lawrence Slater |
| Not specific 'high capacity' - but they did change - what changed I don't know. OS&M notes change of oil pump as Nov '67 - nearly at the end of the original 'CC' engines. My engine was a light metallic green colour and it ran with slightly lower pressures (65) I seem to remember than my mates face lifted one. It was in fairly good nick so not a wear issue. Years later when I put a Gold seal in, the pressures ran as per my mates (70) hot, as have both of my later engines. As I have mentioned previously, when they came into the main dealer as new they normally hit 80 on cold start up - these were facelifted versions. |
| richard boobier |
| You can take the spring to any machine shop that builds cly heads and they can test the spring...it takes a couple of.minutes and thats mostly set up, my shop down the road that I use alot did mine for free Prop |
| Prop and the Blackhole Midget |
| You can measure spring rates at home Spring are rated at lbs/in of travel method Bathroom scales on the bed of you bench drill Squash the spring up exactly 1" and read the rate off the scales If for example your scales read 20lb at 1" compression it is a 20lb spring 2"compression=40lb 3"=60 but still a 20lb spring BUT this does not equal oil pressure unless the diameter of the relief valve is 1 square inch in area From this you can see the more as fitted compression of the spring the higher the seat pressure and resulting oil pressure will be willy Personally I think the std relief valve spring rate is too high and it would be better with a slightly softer and slightly longer spring, compressed to give the same seat pressure to blow off at say 60lb but then be soft enough to push back past the relief port and exhaust the excess oil I'm thinking the standard spring blows off at the correct pressure but because of being too stiff won't allow the piston to move right back till theoil pressure is very high I've seen a pic of this somewhere ,I'll go lookinh |
| William Revit |
| "As a result, if you want a high capacity oil pump today, you can fit the GLP110 Metro/Mini Turbo item. " This may apply to Minis, but not to in-line engines. An OE Metro Turbo pump will not fit under the tin cover, as it is deeper. Don't ask me how I know! |
| Dave O'Neill 2 |
| The oil pressure is really just means of reading how easily the oil is escaping / leaking away in the distribution system. Principally how fast it leaks past the mains and big end bearings, but also, dare l say it, the cam bearings, rocker shaft. Add to that how easily it escapes from the relief valve - this being the only 'adjustable' part of the system. A normally high pressure suggest close tolerances on the crank feeds which is generally what you would want. Although this may also be reducing the volume of flow past the bearing surfaces and reducing the cooling effect at these critical hot spots. Also of course the oil flow is 'shared' between the outlets so an excessively leaky cam bearing will mean less flow and lower pressure at the crank bearings, where it really matters, even if the gauge is still showing a healthy figure. |
| Guy W |
| Hi Guy. Your last paragraph would suggest that if the oil leakage at the camshaft endplate/front journal was reduced, the oil pressure gauge reading should increase. I agree with that, but doubt it could be seen, unless you could do it instantly, like throwing a switch on and off. I agree also that you 'can' look at oil pressure as a means of reading the escape rate from the bearings etc. But that's not really what it is. Oil cant be compresed, - assuming no air content - so it's more a measure of how successfully the oil is keeping moving metal parts away from eachother. Presumabley a figure of 50 psi as often quoted, and is the lift off figure for the relief valve, is the amount needed to do that, and any extra oil pressure is just a waste of the power used to produce it. From that link I posted above, Calver (http://www.calverst.com/ ) says. "50psi hot and flat out with 25psi at idle is all you need. I have used as little as 40psi with no problems." As often as I've said that I don't think I could have 3 oil pressure gauges all reading over by the same amount. I now wonder. My relief valve is lifting. The springs are the correct spec. They weaken with age, not stiffen. The pressure can't be amplified in the oil gallery by a blockage downstream, because this too would be sensed by the relief valve. So assuming the relief 'is' functioning correctly, all that leaves is an incorrect reading on the gauges. They're all made the same way, so maybe they all read high by the same amounts, as they age, which deceived me into thinking that they can't ALL be wrong? So my next step is to test the oil pressure gauge readings. I'm going to try and do that with an air compressor and a tyre valve. As long as I can seal the oil feed tube to the gauge, into a tyre valve, I should be able to 'inflate' the gauge to get a reading on the trye pressure gauge, and compare the oil gauge with it. |
| Lawrence Slater |
| Can't get the pic to copy over- must have copyright or something BUT just looking at it the piston would have to move back about 3/8" to start spilling oil out the relief hole So when the oil pressure blows the piston off it's seat at say 50psi there has to be more pressure to squash the spring up further to clear the hole to get proper relief resulting in high oil pressure A fix would be to replace the long piston with a ball bearing approx 1/16" smaller in diameter than the piston This would allow relief oil to escape around the ball into the relief passage as soon as oil pressure reached the set pressure what do you think willy |
| William Revit |
| Willy: if my measurements are any near right, 5lbs load compresses the spring 7mm (sorry about the mixed units) which I guess is about the diameter of the relief passage. Assuming it needs "x" psi inorder to force the piston to the edge of the passage, it would need a further equivalent of 5lbs to move the rest of the way. Of course, you can't use 5lbs directly because it needs to be calculated as a pressure (lbs/sq in) figure. Work out the area of the piston (can't help as I don't know it's diameter) and divide that in "5" to get psi. |
| Graeme Williams |
| Lawrence, re: " it's (pressure)a measure of how successfully the oil is keeping moving metal parts away from each other" I am not claiming expertise, but think this is more to do with the "film strength" characteristics of the oil than the pressure. Someone could explain knowledgeably about long chain molecules or some such. As you say, as a solid the oil won't compress anyway so, as long as there is sufficient flow over the bearing surface, then the film strength will do the rest. I am pretty convinced that the main purpose of the oil flow is to take heat away from the bearing surfaces. The pump provides the ample flow rate and the pressure is a secondary measure of the degree of resistance in all of the outlets to that flow. The pressure at the bearings must be less than that at the pump or the oil wouldn't flow in that direction? True? I am not sure of that statement! I suppose if it were measured immediately downstream of the bearing then there would certainly be a pressure drop. And theoretically one could therefore progress upstream against the flow in nano-increments noting a progressive increase in pressure all the way back to the pump. |
| Guy W |
| Lawrence Sorry for delay but I've been out and about a lot and in the meantime I think Fergus has provided the figure you need and Willy a way of checking. Here's a (very) rough sketch of what I had in mind:  |
| Peter Blockley |
| Yes the oil pressure doesn't keep the parts apart it serves to replace the oil which gets out the sides. The actual bearing support in the rotating bearings is by the shearing of the oil film creating a sort of wedge of oil the pressure in which supports the journal in the bearing, see http://en.wikipedia.org/wiki/Fluid_bearing . The shearing action does generate some heat and in some engines, high revving race Riley engines in the likes of the Healey Silverstone spring to mind, the oil is pumped through at a higher rate than required to replenish lost oil as the large journal diameters result in enough heating to damage the oil otherwise. |
| David Billington |
| Just confirming what Fergus says, My 1973 workshop manual says: Oil pressure relief valve 50 lb/sq in (5.3 kg/cm2) Relief spring : Free length: 2.86 in (72.64 mm) Fitted length: 2.156 in (54.77 mm) Load at fitted length: 13 to 14 lb (5.90 to 6.35 kg) |
| Peter Blockley |
| And we thought it was just messy black stuff under pressure eh? lol. ;). Hi Willy. I don't think it needs to lift all the way back in order to relieve the pressure. The piston isn't sealed in it's bore. As soon as it lifts, oil is squeezed past it. The higher the lift off it's seat, the grreater the flow past the piston. The drain hole back to the sump is quite a way back, and I don't think the piston is pushed back as far as to align the bullet end of the piston with that hole. Thanks Peter. I might have a stab at that sometime. Meanwhile, I don't think I need to. With an home made adapter, I plugged one of my old spare oil pressure gauges into a small tyre inflation air compressor. The gauge on the compressor agrees with my 2 separate tyre pressure gauges, and the compressor is only about 6 months old. So as best as I can figure, it's approximately accurate. I 'pumped' up the compressor to a reading of 50psi. The oil pressure gauge read 70psi.! :(. I tried a 2nd one. 50 on the compresor read 65 on the oil pressure gauge. I'll plug it in to the gauge in the either the Sprite or the Midget tomorrow. But it appears my oil pressure gauges are reading high, and the pressure relief valve is probably working just as it should. |
| Lawrence Slater |
| I almost forgot...I have a BL manual for the Marina. Under the 1275 engine specs, it has the same details for the spring lengths and load, but it states the relief valve as being 70 lb/sq in (4.92Kg/cm2) It also gives the running pressure as 70 lb/sq in and idling as 15 lb/sq in. |
| Dave O'Neill 2 |
| Maybe they changed the size of the feed hole that the relief valve sit's in? Or increased the size of the return hole? |
| Lawrence Slater |
| Lawrence Your post says "I don't think it needs to lift all the way back in order to relieve the pressure. The piston isn't sealed in it's bore. As soon as it lifts, oil is squeezed past it. The higher the lift off it's seat, the grreater the flow past the piston. The drain hole back to the sump is quite a way back, and I don't think the piston is pushed back as far as to align the bullet end of the piston with that hole." Yep I reckon I agree with that for when the engine is warm and the oil is runny maybee but I still would think that while the oil is cold/thicker the oil can't get through past the piston quick enough causing the need for the spring to be compressed further to allow more piston travel to actually clear the relief port resulting in higher oil pressure Anyway if it is a gauge problem you have it's probably quite ok like it is and not really a problem A bit of the old, if it's not broke why fix it eh We have a bit of a saying here to cover it It's a feature not a fault Cheers willy |
| William Revit |
| Finally got the pic but I suppose it doesn't matter now As you can see there is a fair distance between the sear and the drain for the relief A nice modification would be a relief valve piston which had a smaller diameter back approx. 1/4" ish of it's length from the seat end so that when the piston moved off it's seat the oil could freely pass the smaller diameter section of the piston and escape out the exhaust port BUT it's probably all good as is Too mutch free time on my hands is my problem -----  |
| William Revit |
| Great photo, Willy. The valve seat is actually replaceable.  |
| Dave O'Neill 2 |
| Interestingly, it wasn't available as a spare part, according to Minispares. Currently out of stock! http://minispares.com/search/classic/2a797.aspx |
| Dave O'Neill 2 |
| Cheers Dave Through the heaps of reading I've had time for lately Apparently that seat is different for an auto One seat has holes crosswise to connect into that other oil gallery that goes to the rear main and the other doesn't I'm a bit lost with that -- so far willy |
| William Revit |
| Great picture Willy. What are those drillings I marked with an Ellipse? It looks like a 2nd drain to the sump further back. I'll go and look at my block.  |
| Lawrence Slater |
| Here's a thought. If there was sufficient oil BEHIND the piston, then the pressure in front, would have a hard time lifting it off it's seat. Maybe that's a 2nd pressure relief to prevent that. Now I've really got to inspect my block, because I'm sure I don't have that. |
| Lawrence Slater |
| Prevent hydraulic lock.... Oops forgot the photo.. |
| Malc Gilliver |
Vizard page 400
 |
| Malc Gilliver |
| Willy The auto block is quite different with regards to oil supply. The oil is drawn out of the block by the oil pump through the usual port, but it doesn't come back in the same way as a manual. Here's a pic to show the difference. My local Mini shop built an engine for someone, using an auto block and couldn't work out why they had no oil pressure!  |
| Dave O'Neill 2 |
| Yep, here are the drillings. Looks like a great place to get blocked, and if it did, it would prevent the relief valve from working properly. I'll have to see if mine are clear, as I've only checked the main relief return hole. But back now to the main business of the day, on oil sucking. :).  |
| Lawrence Slater |
| Lawrence I'm not sure how easy it will be to check without removing some plugs. I think the horizontal drilling is to re-route the oil to the main drain hole.  |
| Dave O'Neill 2 |
| Well at least Peter's spring data confirms my measurements of 11 lbs and 15mm compression. THat equates to just over 13 lbs for the fitted length quoted which is a good match for the 13 to 14 lbs pre-load from the same table. Can someone tell me the diameter of the plunger? |
| Graeme Williams |
| Hi Guys Lawrence I know you are happy with your relief valve as manufactured and as they say - If it ain't broke why fix it But as I have heaps of time on my hands I sit and think a bit too much This is a pic. -not to scale - of what I think a modified piston could look like to allow easy oil flow to the exhaust port as soon as the piston starts lifting off it's seat - OR a ball bearing at the reduced diameter to let oil flow around it would operate the same way. I guess at worst we all learn a little extra new stuff to forget willy  |
| William Revit |
| Hi Willy. Nah. No mod's of the relief valve for me, I'm tied up with oil sucking. :). Anyway, I think it works well as designed, as long as the bullet is free to move without binding. Your pic, even though not to scale, does pretty well represent an accurate depiction though. The piston can't travel so far back as to completely uncover the main excess oil return hole. Even with the spring fully compressed to 31 mm or thereabouts, the combined length of the piston and the spring is simply too long for the piston to be pushed back that far. Fully compressed it takes 32lbs, and is 31mm long. So where does the 50lbs come in. I'm not sure if that matches the figures quoted earlier for compression rate, but since it returns to 72mm when not compressed, I'm happy with it. Hi Dave. No need to remove plugs to confirm clear passages. I blocked the main return hole from inside where the piston sits, using a rubber bung on the end of a probe. Then I blew from the flange end on the relief drain to the sump. I was able to easily blow air through the secondary hydraulic lock prevention hole. Completely clear. Meanwhile, I did a quick check on the oil presure gauge in the Sprite. It too is reading high, with a progressive error rate. It appears to be high by about 20psi, at circa 85/90psi on the Sprite gauge, when compared to the compressor gauge. I doubt my compressor gauge is that accurate, but I think it confirms that all my oil pressure gauges are reading high, which is NOT what I'd previously thought. This confirms for my engines definitely, that overly high oil pressure --- 'in the main gallery' --- is not the cause of too much oil in the timing chain cover, and so not the cause of oil sucking. But see that thread for an update. |
| Lawrence Slater |
| Bugger, forgot the picture. So I'll repeat the post. Hi Willy. Nah. No mod's of the relief valve for me, I'm tied up with oil sucking. :). Anyway, I think it works well as designed, as long as the bullet is free to move without binding. Your pic, even though not to scale, does pretty well represent an accurate depiction though. The piston can't travel so far back as to completely uncover the main excess oil return hole. Even with the spring fully compressed to 31 mm or thereabouts, the combined length of the piston and the spring is simply too long for the piston to be pushed back that far. Fully compressed it takes 32lbs, and is 31mm long. So where does the 50lbs come in? I'm not sure if that matches the figures quoted earlier for compression rate, but since it returns to 72mm when not compressed, I'm happy with it. Hi Dave. No need to remove plugs to confirm clear passages. I blocked the main return hole from inside where the piston sits, using a rubber bung on the end of a probe. Then I blew from the flange end on the relief drain to the sump. I was able to easily blow air through the secondary hydraulic lock prevention hole. Completely clear. Meanwhile, I did a quick check on the oil presure gauge in the Sprite. It too is reading high, with a progressive error rate. It appears to be high by about 20psi, at circa 85/90psi on the Sprite gauge, when compared to the compressor gauge. I doubt my compressor gauge is that accurate, but I think it confirms that all my oil pressure gauges are reading high, which is NOT what I'd previously thought. This confirms for my engines definitely, that overly high oil pressure --- 'in the main gallery' --- is not the cause of too much oil in the timing chain cover, and so not the cause of oil sucking. But see that thread for an update.  |
| Lawrence Slater |
| What happens to the oil pumped to the front mains? Does it drain back into the sump directly? I presume it doesn't connect with the front bearing oil drain holes? |
| Guy W |
| It pumps to the big ends, the front camshaft bearing, and out of the front to the TCC, where is drains back to the sump, --- after flooding the TCC that is. lol. |
| Lawrence Slater |
| If the replaceable 'seat' was a poor fit, can high pressure oil get past the seat and go straight into the main oil gallery??? In the pic posted by Willy on 22nd Jan, it looks as if a loose replaceable seat could move instead of the relief piston and that would allow oil to go to that drilling that runs to the rear main, and presumably the front main too.  |
| r thomas |
| Good point rt But I'm led to believe from a local mini guru that it is almost impossible to get the seat out and never come out on there own But I guess there's always a first time for everything willy |
| William Revit |
| That photo's getting a lot of use ;o) Apparently, the best way to remove the seat is to tap a thread into it and wind it out with a bolt. |
| Dave O'Neill 2 |
This thread was discussed between 20/01/2015 and 24/01/2015
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