oil pressure vs rod clearance?

[Mike Bartlett]

not sure yet but my loss of about 15-psi in oil pressure may have to do with my new rod bearings. I may have made a mistake in my measuring still checking other things that may explain the loss in pressure. IF.....my mistake was in measuring the crank rod journals so I have maybe a .010" turrned down crank but stock new rod bearings what would acceptable oil pressure be to not having to go back into the engine. I am currently running about 40-45-psi at cruise speed and 10-psi at idle. Is this pressure “ok” even though I may have a larger gap between the rod bearings and journals? I am using 15/40 oil with about 3-qts of the 10-qts total being 5/30. Obviously thicker oil, maybe 20/50, will increase the oil pressure some? Is pressure the only concern or even with "acceptable" pressure is the rod bearing gap unacceptable no matter what the oil pressure is??

Thank you,

Mike

[Woodz428]

If you had such a mismatch, you'd probably have NO oil pressure and some knocking rods. You may have .001 or .002 polished undersize that could create a drop in pressure, but not a .010. The cruise rpm doesn't seem too bad but I would not want only 10 psi at idle. Loose clearances are aided by a high volume pump, but I'd probably yank the pan and re-do it.

[CobraV8]

Originally Posted by Mike Bartlett

Is pressure the only concern or even with "acceptable" pressure is the rod bearing gap unacceptable no matter what the oil pressure is??

Absolutely, there's a good reason for checking play (i.e. with plastigage) before assembling the rotating assembly. An undersized crank wiht standart bearings will result in wearing out the crank journals quickly.

Simon