Correct oil pressure for a 69 L88

[Jon S.]

The responses to a recent post asking about the proper oil for use in a 396 have gotten me to thinking. I've always felt like my L88 was not holding enough oil pressure at idle, however Joe's response to the other thread was:

"If the engine is set up so loose that it actually needs this heavy of an oil to maintain proper oil pressure, that's the more serious problem. Engines set up with loose clearances are fine for racing purposes."

I've been told that the L88s were built loose since they were intended for racing, so would that imply that it should carry a lower oil pressure than other motors? What kind of oil pressure should a fully warmed up L88 carry at idle in it? How about at a normal highway speed? I'm running straight 40W oil now, would I be better off switching to the 20w50 racing oil?

I'm trying to prep my car for a PV, and oil pressure is one of the things that I'm worried about passing since the PV manual states (I think, I don't have it in front of me right now) that all engines should have about 30 psi of pressure at idle. Mine is a bit below that figure.

Thanks,
Jon #10673

[Joe L.]

Re: Correct oil pressure for a 69 L88

John-----

The key words in the previous post of mine which you described were "...ACTUALLY NEEDS...". In other words, if an engine is set up so loose that it "ACTUALLY NEEDS" 15W-40 oil to maintain proper oil pressure, that could mean that it's set up too loose for dependable, long-term street service.

All 1969 Corvettes, including L-88s, should operate with normal oil pressure using 10W-30 weight oil. However, for ambient temps above 20 degrees F, 10W-40 or 20W-40 were approved engine oil viscosities. In my opinion, the latter 2 viscosities would be the preferable ones for use in an L-88. But, the L-88 engine should maintain normal oil pressure with 10W-30.

L-88s used a standard volume, high pressure oil pump. The high pressure pump was designed to "overcome" or compensate for some of the "looseness" in the engine set-up. Idle oil pressure shoud be about 20-25 psi. Keep in mind, however, that the original in-car oil pressure gauges are rather notoriously inaccurate. Usually, they read 5 to 10 psi LOW. To determine what actual oil pressure that your engine is running at, you need to temporarily install an accurate, high quality test gauge.