427 CBB oil pressure

[70RS/SS396]

Hi

I have a 427 cbb motor, 80s stocker built. L88 with stock L88 camshaft.

The motor have a stock GM modified oil pump (anti-cavitation grooves).

The oil pressure is very stable, about 18-20 psi at idle and then it goes up to about 42 psi when I hit the throttle. but then even If a run the motor in 7000 rpm I never have more then 42 psi oil pressure.

I run quaker state 20w50 mineral oil. Have also tried 15w40 mineral, but with no difference.

The motor ran straight 40 quaker state oil when it was raced in the 80s.

Is it safe to run this motor with the low pressure? with the 20w50 oil.

Thank You

[Alan Roehrich]

I'd want to look at the oil pump and find out about the clearances, as well as the condition of the bearings.

The idle oil pressure is fine, for a hot idle at 750-1000 RPM, but the high RPM oil pressure is a bit low for 20W50.

You may well get by with it, but it is not what I'd call ideal.

[70RS/SS396]

Originally Posted by Alan Roehrich

I'd want to look at the oil pump and find out about the clearances, as well as the condition of the bearings.

The idle oil pressure is fine, for a hot idle at 750-1000 RPM, but the high RPM oil pressure is a bit low for 20W50.

You may well get by with it, but it is not what I'd call ideal.

Is it better to run 15w40 ?

[Alan Roehrich]

Originally Posted by 70RS/SS396

Is it better to run 15w40 ?

I don't know that 15W40 will be any better.

I'd suggest you try 20W50 Racing Valvoline, or Brad Penn, if you want to run mineral base oil.

[tj310]

Try it with 10- 30 if it's the same I say your OK---Trevor

[SSGN]

Bad oil pressure gauge???Been their done that,just a thought

Kevin

[pmrphil]

if the gauge is OK you might want to consider changing the bypass spring in the pump - as Alan said, not ideal pressure at RPM

[Alan Roehrich]

That is why I suggested a look at the pump. In an engine that old, it is possible that the oil pump bypass spring is bad.

Yes, the gauge too is a possibility. I did not mention it and should have. I always check my gauge right after I check my oil and filter if I have an oil pressure problem. I need to remember not everyone does.

Speaking of oil filters, I suggest using either a long Wix racing filter, or a long K&N filter. By long, I mean the 1 quart filter. Oil filters have been known to cause that problem. I've even seen it with what used to be good filters, the AC PF1218 included. The only AC that may still be good is a PF2232 Duramax filter, but I'd check to see before I used it, and it will be the same price as a K&N or Wix Racing, and you'll know what you have then.

[70RS/SS396]

The motor is modified like this, I know that the oilpump is modified to give this pressure. And they rew this motor 7400 rpm when it was raced in the 80s. But I dont want to risk anything now, ......so there isnt any problem with the pump or oilfilter but is it safe to run a cbb with this oil pressure?
But What oil should I run 40 or 50 ?

Thanks

[james schaechter]

Originally Posted by 70RS/SS396

The motor is modified like this, I know that the oilpump is modified to give this pressure. And they rew this motor 7400 rpm when it was raced in the 80s. But I dont want to risk anything now, ......so there isnt any problem with the pump or oilfilter but is it safe to run a cbb with this oil pressure?
But What oil should I run 40 or 50 ?

Thanks

If this hasn't seen daylight since the 80's it sure would be a good idea to pull the pan and look it over if you can. Much cheaper to do that than to wait for trouble.