Ian Vincent Posted November 22, 2018 Report Share Posted November 22, 2018 Regular readers may recall that I raised a concern about slightly low oil pressure a couple of months ago. I think it was Mick who suggested it could be down to excessive end float on the crank. I have the gearbox out at the moment so I put a dial gauge on the end of the crank and levered it back and forth to get a repeatable figure of 0.18mm or 7.1 thou. This is outside the recommended workshop manual range of 4 to 6 thou. Is it significant and should I be thinking about replacing the thrust washers? Rgds Ian Quote Link to post Share on other sites
Motorsport Mickey Posted November 22, 2018 Report Share Posted November 22, 2018 Yes. Mick Richards Quote Link to post Share on other sites
DaveN Posted November 22, 2018 Report Share Posted November 22, 2018 +1 because it will only get worse. I recommend Scott Helms at custom thrust washers. Customthrustwashers.com plus a simple job to do giving you the opportunity to get an idea of how good the main bearing shells are as you have to remove the no.4 bearing cap and also clean the sump out! Quote Link to post Share on other sites
Ian Vincent Posted November 22, 2018 Author Report Share Posted November 22, 2018 Thanks guys. That’s what I like, nice unequivocal answers. Rgds Ian Quote Link to post Share on other sites
Motorsport Mickey Posted November 23, 2018 Report Share Posted November 23, 2018 " how good the main bearing shells are as you have to remove the no.4 bearing cap and also clean the sump out!" Dave, There ain't no number 4 main bearing on a 4 cylinder crank ! I know...I've looked Mick Richards Quote Link to post Share on other sites
DaveN Posted November 23, 2018 Report Share Posted November 23, 2018 Haha sorry I’ve got a six pot!..... didn’t know there were engines made with less than six cylinders Quote Link to post Share on other sites
Tonyloz Posted November 23, 2018 Report Share Posted November 23, 2018 +1 for scott helms Quality product with good delivery time If your in there change the b end shells..can only help to get your pressure back and will give u a heads up on the mains...cant remember if you can change the mains in situ Good luck Quote Link to post Share on other sites
Motorsport Mickey Posted November 23, 2018 Report Share Posted November 23, 2018 (edited) Just remember guys, don't go chasing pressure, it's flow that counts. As long as the loss of oil from sides of bearings etc is balanced by the incoming flow. Mick Richards Edited November 23, 2018 by Motorsport Mickey Quote Link to post Share on other sites
RogerH Posted November 23, 2018 Report Share Posted November 23, 2018 .........and it is the flow that helps remove the heat................ Roger Quote Link to post Share on other sites
stuart Posted November 23, 2018 Report Share Posted November 23, 2018 37 minutes ago, Motorsport Mickey said: Just remember guys, don't go chasing pressure, it's flow that counts. As long as the loss of oil from sides of bearings etc is balanced by the incoming flow. Mick Richards 1920`s LeMans Bentleys only ran 8PSI oil pressure but had several gallons of it sloshing round the engine Stuart. Quote Link to post Share on other sites
Waldi Posted November 23, 2018 Report Share Posted November 23, 2018 I’m eager to learn: Why would the thust washers impact oil pressure when worn? On a 6-pot the other 3 main bearings are of a similar design with no TW at all, so why would it matter? Additionally. the TW is only on 180 degrees of the circumference. Or is the 4 pot of a different design? Thanks, Waldi Quote Link to post Share on other sites
j-eichert Posted November 23, 2018 Report Share Posted November 23, 2018 Just my 2 Cents: - Thrust washer in a 4-pot consist of 2 half-circles each - Impact on oil pressure - why? - there is just one set of thrust washers as this bearing is designed as the one taking the load. If there would be more than one , there would always be only one "working": So keep it simple (and cheap) and skip the others….. - pressure is necessary to make a fluid flow. So without pressure: No flow at all. - The pressure is measured in the oil gallery - this pressure is dependant from the oil pump, setting of pressure restrictor AND the flow resistance of the oil channels after the measuring point. - first (and main?) factor is the main bearings. Worn bearings loose as t lot of oil -> thus the oil pressure is reduced. - The flow through the big end bearings depends on the flow through the main bearings: So worn main bearings reduce flow in the big end bearings - the oil flow into the head depends (4-pot) on the rear main bearing: Worn bearing -> less oil in the head Rebuilding my engine gave me much higher oil pressure with much more oil in the head - so (TR3 with "open" oil cap) so I lost oil by dripping out of the oil cap Regards, Johannes (Sorry for my english …) Quote Link to post Share on other sites
RobH Posted November 23, 2018 Report Share Posted November 23, 2018 "pressure is necessary to make a fluid flow. So without pressure: No flow at all." Well I know what you mean Johannes but that is not really true - it's actually the other way around. Pressure results from a restriction of flow. If you ran the pump with nothing attached to its output there would be plenty of flow but no pressure. Its the restriction due to tight clearances in the bearings which produces the pressure at the pump by reducing the flow. Quote Link to post Share on other sites
j-eichert Posted November 23, 2018 Report Share Posted November 23, 2018 Rob: even then you need some pressure (even a milli-psi is pressure). And just lifting the oil from sump to head needs some pressure too You are right: 1 hour ago, RobH said: Pressure results from a restriction of flow. But keep in mind that any kind of pipe or passage is a restriction of flow - and high flow until the main bearing with direct exit into the sump doesn't help you with lubricating the big ends or the rockers Regards, Johannes Quote Link to post Share on other sites
Spit_2.5PI Posted November 24, 2018 Report Share Posted November 24, 2018 Of course it's not pressure, but a difference in pressure that's needed for fluid to flow. Cheers, Richard Quote Link to post Share on other sites
Steves_TR6 Posted January 19, 2019 Report Share Posted January 19, 2019 Morning all too cold to do much in the garage so thought i’d check the end float on my 6 i had a lot of difficulty finding somewhere suitable to mount the dti, eventually the magnetic base was attached to the block and i got a reading of 14 its a metric dti so this equates to 5.5thou so ‘acceptable’ however i’m not confident in the reading, as i’m new to using the dti and wasnt happy it was mounted stably enough does anyone have a picture of how they mounted a dti to a 6pot in the car successfully? steve Quote Link to post Share on other sites
Ian Vincent Posted January 19, 2019 Author Report Share Posted January 19, 2019 I can't help with where to mount the DTI Steve but all I was concerned about was getting a repeatable reading. So I moved my DTI around a couple of times and confirmed that I was getting the same reading each time. If I were you I would be looking to do the same sort of thing. Rgds Ian Quote Link to post Share on other sites
Waldi Posted January 19, 2019 Report Share Posted January 19, 2019 Hi Steve, the DTI should be on the block, not on the frame, but this is Obvious. I messured mine when the engine was on an engine stand with camshaft chain cover off so had no issue then. You could check if it is firmly mounted by adding a feeler gave between the point of the DTI and your pulley, then check if the reading changes the same rate. Regards, Waldi Quote Link to post Share on other sites
RogerH Posted January 19, 2019 Report Share Posted January 19, 2019 Hi Steve, I know this is silly but to interpret your reading of '14' without conversion tables. Place the DTI on a flat surface and slide feelers under the tip to get near your reading. As for stability. When attached to the engine block can you get ANY movement on the pillar of the DTI. You should not. Roger Quote Link to post Share on other sites
Ian Vincent Posted January 19, 2019 Author Report Share Posted January 19, 2019 (edited) 4 hours ago, RogerH said: I know this is silly but to interpret your reading of '14' without conversion tables. Place the DTI on a flat surface and slide feelers under the tip to get near your reading. Alternatively divide 0.14 by 25.4 to get the exact figure of 0.0055, (to 4 significant places) Rgds Ian Edited January 19, 2019 by Ian Vincent Quote Link to post Share on other sites
RogerH Posted January 19, 2019 Report Share Posted January 19, 2019 Hi Ian, indeed the conversionn works very well. But I read it as if the reading of '14' was just that = 14 what !!! It is often nice to see what you are actually playing with. Roger Quote Link to post Share on other sites
Steves_TR6 Posted January 19, 2019 Report Share Posted January 19, 2019 1 minute ago, Ian Vincent said: Alternatively divide 0.14 by 25.4 to get the exact figure of 0.0055, (to 4 significant places) Rgds Ian Yes, maths is your friend! i’m planning to measure a few more times and see what results i get. if the endfloat is within limits i’ll leave well alone, otherwise it’s off with the sump, fit std washers, retest, order the correct size. thanks for the input ! Quote Link to post Share on other sites
Waldi Posted January 19, 2019 Report Share Posted January 19, 2019 With metric DTI’s “we on the mainland” normally work in hundreds of mm. 25,4 units on the scale equals 25,4/100 mm which is 0.254 mm which is 10 thou (or 1 thou equals 0.0254 mm) I had to get used to thou’s too. Waldi Quote Link to post Share on other sites
Steves_TR6 Posted January 20, 2019 Report Share Posted January 20, 2019 (edited) After much trial i found a solid location for the dti and obtained repeatable end float readings of 16-17=6.2-6.6 thou so i guess i’ll be having the sump off ! wonder what i’ll find, as the engine is ‘bespoke’ ie i dint know whats been done exactly...... steve Edited January 20, 2019 by Steves_TR6 Quote Link to post Share on other sites
aardvark Posted January 20, 2019 Report Share Posted January 20, 2019 Where did you put the dti in the end Steve? cheers dave Quote Link to post Share on other sites
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