Here we go again; oil pressure for the S/B C2's

[Larry E.]

Have a friend (Not NCRS member) that has a nice 66 Base engine coupe. Upon cold start-up the
oil pressure gauge(60#) needle "pegs" the 60# reading. It stays pegged for long time until the
engine(L75) gets some heat in it. It does not come down very much; always close to 60#. Is this
normal for this C2? Seems like a lot of old threads on this discussion board brings this subject up often.
Not sure but it looks like the oil pan has never been dropped so someone putting in a heavier spring
in the oil pump is remote. (That's my guess) The only thing I see that is different from stock is that
someone put in an oil filter adapter that uses the spin on filter. (PF25) Would this change the oil
pressure in any way?? Thanks in advance. Larry

[Terry D.]

Re: Here we go again; oil pressure for the S/B C2's

First I don't know how after 50+ years you could tell if oil pan was ever removed. If it was done early on how would you tell?
Second, change the oil filter adapter and see if it makes a difference, I doubt it but stranger things have happened. When was the last time he changed oil and what kind of oil is he using? Was the engine ever rebuilt? Was the gauge ever out? I think we need a little more info.

[Timothy B.]

Re: Here we go again; oil pressure for the S/B C2's

Larry,

Regardless if the gauge is in question or the oil pump has been changed the fact remains that the oil pressure is not normal, the factory spec for max pressure is 45psi.

My GUESS and $$$ is on the oil pump but be careful what you install if he drops the pan because these aftermarket pumps come with a high pressure spring.

[Duke W.]

Re: Here we go again; oil pressure for the S/B C2's

The OE spec for all small blocks oil pressure is 40-45 psi, engine fully warmed up, at 2000 RPM, EXCEPT late '63 and up mechanical lifter engines, which is 55-60 psi at 2000. The former should have a 60 psi gage and the latter an 80 psi gage.

It is all too common for rebuilders to replace OE pumps with a high volume/high pressure pump. This is totally unnecessary, but it happens all the time. The solution is to replace it with a standard volume/standard pressure pump, however, none of these that I am aware of have a proper OE equivalent spring, and they will usually still read somewhat high.

Another solution is to remove the pan and pump and install an OE spring, even if it is a high volume pump that has longer gears than a standard volume pump, but why not just replace it with a standard volume pump. They aren't expensive. Both OE springs are available from GM and Joe L. has posted the part numbers multiple times. So even if you buy a new standard volume/pressure pump, replace the spring with the GM original or oil pressure might still be too high.

Excess oil pressure is primarily a judging issue. It could be noted during ops check and will likely not pass a PV. Functionally it will do no harm, but a high volume/high pressure pump will take a bit more power to drive and may result is slightly higher oil temperatures.

Duke

[Larry E.]

Re: Here we go again; oil pressure for the S/B C2's

Thanks to all the response. Yes it is true that nobody really knows the history of this particular L75. It just seems to me(something fishy)
that with all the past threads on this discussion board with similar issues that "ALL PROBLEMS ARE DUE TO WITH A BIGGER SPRING
IN THE OIL PUMP or DIFFERENT TYPE OF PUMP(HIGH VOLUME)". Could it be possible that some small blocks where off various tolerance when machined that would
cause this? At any event I will tell him to just leave it alone as like Duke says it will cause no harm. Thanks again-Larry

[Duke W.]

Re: Here we go again; oil pressure for the S/B C2's

Thanks to all the response.

Could it be possible that some small blocks where off various tolerance when machined that would
cause this?

No, that would be essentially impossible. I can't tell you how many guys have told me that such and such was all original from the plant never disassembled, rebuilt, etc. when there is clear evidence that the claim is false.

My favorite is the guys who say my small block has never been apart from the plant and then I measure head gasket thickness at something around .035". All small blocks from at least '57 to the early seventies were built with a .018" steel shim gasket, but it was not available through service parts since at least the mid sixties. At that point the service part gasket was a few thou thicker and had a different part number - probably to compensate for the typical surface cut taken if the heads were removed for a valve job.

Duke

[Loren L.]

Re: Here we go again; oil pressure for the S/B C2's

Be aware that this car when delivered would have come with 30W or a 10W-30W NON-synthethic oil, considerably different from what MAY be in the crankcase today. And perhaps some of the 40ish PV judges crusading against high volume oil pumps should be aware of this item on page 6 of the July 1965 Chevrolet Service News:

"HIGH ENGINE OIL PRESSURE!
Corvette 327 cu. in. - 365-375 HP
The above 327 cu. in. high performance Corvette
engine oil pressures in the area of 80-95 psi (at
2000 RPM) CAN BE EXPECTED AND ARE PERFECTLY
NORMAL. However, damage may occur to this if the
283 cu. in. engine oil pump is used which delivers oil
pressure of 65 psi at 2000 RPM." (Caps added.)