Re: 1939 super 8 oil pressure

Posted by Owen_Dyneto On 2009/6/1 12:18:58

My engine seems to run with a low oil pressure at speed and when cold, it never indicates much over 40 psi which I think is just over half way up the guage. At idle it doesnt drop much under 30 either. I dont know what oil is in it and may change it so that I know it has a suitable classic grade 20 - 50.

My 320 engine, reasonably fresh rebuild with babbitt mains and rods, idles hot at 20 lbs +/-, runs at hot road speed at 45-50, and I've set the pressure relief valve to cut off the maximum at about 55 - seen too many ruptured oil filter canisters from higher cold pressures. I run straight SAE 30 detergent, daylight temps in the summer here rarely into the 90s.

If yours never get above 40, I'd think perhaps you'll want to adjust your pressure relief valve. If in fact the cold idle pressure does increase above the 40 you now see with more tension on the plunger spring, I'd set to max to about 55-60 but no more. You might also want to check the accuracy of your gauge.

If you can't get above 40 psi with a cold engine and you've checked the accuracy of the gauge, I'd guess something internal isn't entirely up to snuff but I'd also speculate that you have enough pressure for safe engine performance.