hello,
for a number of months i have been driving my 1100 around with low oil pressure, ruffly 5psi at idle of 1350 revs (40w-70 oil with 2 bottles of stop smoke:s) and drive at 60km/h pressure of 15-20ish psi depending on outside temp. engine has now been stripped and looked at and is baffeling.

oil pump was quite scored and cratered but mechanic has seen worse with much better oil pressure

bearings main and big end were about 90% so donno there...

crank doesnt look at all worn 010 oversize

bore has no lip at all 020 over size

rubber o ring was not missing between gearbox and block

i dont really no what else to look for so any suggestions on this topic would be helpful

cheerz,
matt

have you checked it with a mechanical oil guage to make sure that the real reading. It could just be a faulty guage or clagged capilary.

well my guage was mechanical but it was tried also tired with another smiths oil guage

Did you check the oil pressurue relief valve was working properly?

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yep also changed it to a cv ball, was getting better cold oil pressure 70psi but when the warm approached low low low again.

What about the running clearance on the crankshaft thrust washers?

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1964 998 Cooper , 1968 Morris 1100

ok that one i have no idea about how badly can thsi affect oil pressure?? should i replace the thrust washers??

Thrust washer clearance won't affect pressure- my 1310 had .014" crank end float when I pulled it down due to a piston problem, oil pressure was still 70psi when hot, 25W/50 oil.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Is it possible the block is cracked, and when it gets hot the oil goes through the crack? Just an out there possibility

thats somthing i havnt thought of i shall inspect everything that i can see and if nothing come arcoss my eye i shall rebuild it as per normal and hope for the best i guess.

cheers

Did you put a bit of steel rod (5/16"/8mm dia x 40mm long) inside the spring? If not, the spring can flick the ball out of the seat so it doesn't seal properly, pressure then drops to 10-20psi.
The bit of rod prevents this happening, I've done about 12 motors with this mod and it works.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.