nascar57

I just had my 350 in my 72 rebuilt by a reputable engine shop. We did go with a roller cam, lifters but its pretty much stock. Fired it up and had 70 psi idling. Came down to 55-60 once warmed up but still saw 90+ psi at 3000 rpm. Much too high for going down the road! The engine has 10w40 oil. Engine builder says try a lighter weight oil but I dont buy that. Is it possible the oil pump pressure relief valve is stuck?
One question I have is If I need to try a new pump or check the relief valve, can the oil pan be removed without removing the engine in a corvette? Certainly dont want to pull the engine again!!

bjankuski

Try a 5/20 oil, very easy to do.

7t9l82

I wouldn't worry about it, it sounds like the builder put a good pump in and hour clearances aren't sloppy. I don't see a problem. It will keep the engine well lubed. After break in use a synthetic oil.

ctmccloskey

When I had my 427 rebuilt they put the High pressure spring into the pump. It was too much oil pressure for an older Big Block engine. I took the car to a Corvette Specialist who (had a Lift) put the standard spring back into my oil pump for me. It was able to be done with the engine in the Corvette. My C3 is a 1968 and has enough room for them to remove the oil pan and oil Pump from below the Corvette.

The Engine Builder should know the clearances used for the main bearings and that is used to determine the oil weight used. I use a 5w30 in my 427 and it works great. Today's cars have tighter tolerances than cars used to. This is why they use the newer lighter weights of oils. My BB was rebuilt using tighter tolerances and the thicker oil is not the best for it.

REELAV8R

Yes, the oil pan can be removed without removing the engine. My gauge only goes up to 70 psi, you got one that goes to 90? I guess I'd want to verify that reading before I started changing things.

MelWff

Disconnect the idler arm from the frame to drop the pan.

nascar57

i hooked up an external oil pressure gauge to the fitting above the timing cover and verified the pressures. Same as the in car gauge. going to try 5/20 oil.It has a new high volume pump so if the oil doesnt work I might have to check the relief valve in the pump.

Gunfighter13

Close tolerance built engine with high volume/pressure pump. Just run some 5-20 or 10-30 mobile one and it should be fine....Will also add that continuing to run that engine with extreme high oil pressure will cause bearing failure.

Gunfighter13

Do you know what pump was used? Make and model?

Engage

That's not too bad.... my 383 runs the same pressures with 15/40..... if it still makes you nervous try a good synthetic 5/30 after break in

nascar57

changed the oil to 5w20 seemed to help a little but still have 80+ psi at 3000+ rpm. Engine builder was just here and he says drive it for awhile to see if anything changes. He was a little concerned about the high oil pressure but didnt think the relief valve was stuck because the pressure varies with engine rpm. He said if the valve was stuck it would probably blow the filter off as he has seen it happen a couple times.

nascar57

New high volume pump, not sure which brand.

nascar57

that is what worries me. Going down the road with 70+ psi oil pressure. I'm worried that the plastic line or the gauge will fail or the filter will blow apart also.

Buccaneer

OK, I don't see how high oil pressure causes "bearing failure", please explain this, I'm all ears.

I have a somewhat tight tolerance motor. The pressure cold using 10W40 Dino oil as directed by the lifter manufacturer - Morel, is 75-80psi, warm is around 60-65psi. I personally like high oil pressure since your rotating assembly rides on the thin film of oil, not on the bearings. If they did, you will have bearing failure along with parts failure which is what happens with low oil pressure.

To the OP, I really wouldn't worry about it unless the pressure drops way down. It may be possible the relief valve is stuck. You could test that real quick and blast it a couple times WOT and then see if the pressure comes down a bit. If not, I wouldn't worry, you do have a high volume pump probably like mine installed which is a Melling M55HV pump.

bjankuski

It won't.

Haggisbash

I suggest doing a read up on high volume oil pumps in small block engines, I have seen more than one write up that suggested they are not necessary and can cause issues.

jackson

the more oil your pump is pushing and/or the harder it's pushing it ... the more horsepower it's using ... and (on wet sump sbc-BBC) putting that much more stress on cam-dist drive gears

REELAV8R

The spring on the pump bypass can be changed to lower oil pressure.

I would agree that a high volume pump is overkill, wears on the distributor drive and uses excess HP.

7t9l82

The only time I have seen a high volume oil pump cause a problem is when the car was running 2 quarts low on oil and the dimwit was hot ******* the car.
The horsepower loss is not significant. And if you have a flat tappet cam it darn sure won't hurt to have a little more oil. I had an oil filter burst at 160 m.p.h about 35 years ago. And it was a fram filter after that I switched to Hastings filters because the steel was much thicker. Since then lots of filters have gotten better. I. Doubt 70 lbs will cause an issue with a quality filter. So much misinformation about oil pressure. I have a melling select pump with an 8 quart milodon pan and holds about 70 pounds hot with 20w50 synthetic..

jackson

Not saying don't run hi-po pump ... just be aware nothing's free.
OE / stock rebuild sbc-BBC don't NEED more than OE pump.

That said, for many non-OE & endurance builds, I like M 10552 + 10% volume.