[69chevyLWB]

Fired up my rebuilt 388 chevy (350 bored .060 over and 3.75 crank) and it ran prefect but the oil pressure at 2500 was at 80 psi and would keep climbing the higher the rpms went. Got up to 4000 and she was close to 100lbs! we shut the motor down after this and had no leaks or other problems. Oil pump is in a package from summit which came with a 7 quart pan and a pickup. oil is straight 30w. no oil leaks or gaskets blowing out. just wondering if the relief spring isnt working or whats going on. bearing clearances are around .02-.03

[vinniekq2]

I have similar oil pressure and my engine is 9 years old

[Greg T]

Mine is like that. also. I am changing to 5W-30 oil this summer.

[Richiehd]

Put some 10-40 in. Whats the pressure hot? Probably 40psi at idle?

[cobalt327]

Originally Posted by 69chevyLWB

Fired up my rebuilt 388 chevy (350 bored .060 over and 3.75 crank) and it ran prefect but the oil pressure at 2500 was at 80 psi and would keep climbing the higher the rpms went. Got up to 4000 and she was close to 100lbs! we shut the motor down after this and had no leaks or other problems. Oil pump is in a package from summit which came with a 7 quart pan and a pickup. oil is straight 30w. no oil leaks or gaskets blowing out. just wondering if the relief spring isnt working or whats going on. bearing clearances are around .02-.03

Straight 30w oil is thicker when cold than multigrade motor oil (like 10 or 15w-30 or 40, like you'll presumably be using after it's broken in).

And the engine is spanking fresh. Likely once the cam's broken in and you are running the oil you'll normally be using, you'll see a reduction in the hot oil pressure.

If not, then I'd be looking into the pump bypass spring being too stiff or piston sticking shut. Also be sure the gauge is accurate.

[steeny]

If it is a true reading of oil pressure check the bypass. I blew a BBC oil filter off and made a big mess. Same scenario, high oil pressure that just kept rising.

[69chevyLWB]

Never checked oil pressure at idle because the engine was on break in so i tried not to let it idle. oil was never up to operating temp because we only ran it til water temp went to around 160 or so. Hoping that when we change to 10w-30 it will decrease some of the oil pressure.

[cobalt327]

You did right by not idling it before the cam is broken in. Keep us posted.

[69chevyLWB]

Okay so do you think i should continue with break in procedure? The oil pressure is around 80 when rpms are around 2500.

[painted jester]

Yes continue your break in!!! Your ok unless your running a cheep chinese knock off filter that can burst

Jester

[cobalt327]

Originally Posted by 69chevyLWB

Okay so do you think i should continue with break in procedure? The oil pressure is around 80 when rpms are around 2500.

Yes, as long as you're using break in oil or an additive that has ZDDP in it. And the cam should have had break in lube applied to it, too unless it's a roller.

[painted jester]

Originally Posted by cobalt327

Yes, as long as you're using break in oil or an additive that has ZDDP in it. And the cam should have had break in lube applied to it, too unless it's a roller.

Thanks cobalt for adding that: I took for granted he did that because he already started his break in LOL

Jester

[69chevyLWB]

Yes it is break in oil and the filter is a moroso unit. break in lube has been applied. isky's rev lube. i will continue with break in and let you know how it goes.

[oldbogie]

Originally Posted by 69chevyLWB

Fired up my rebuilt 388 chevy (350 bored .060 over and 3.75 crank) and it ran prefect but the oil pressure at 2500 was at 80 psi and would keep climbing the higher the rpms went. Got up to 4000 and she was close to 100lbs! we shut the motor down after this and had no leaks or other problems. Oil pump is in a package from summit which came with a 7 quart pan and a pickup. oil is straight 30w. no oil leaks or gaskets blowing out. just wondering if the relief spring isnt working or whats going on. bearing clearances are around .02-.03

I suppose one big thing to ask is what is the temperature around engine? If it's extremely cold, by that I mean freezing and lower, the oil will be very thick. It could be so thick that even with the bypass open the amount that can pass thorugh the bypass hole is not sufficient to lower pressure inside the engine. If this is in a very cold place I recommend dropping the oil from straight 30 to 5W20. Surprisingly most oils straight, multi, mineral, synthetic all tend to congregate in a fairly tight viscosity range at 200 degrees F, but at freezing and below the viscosity differences are very large. So frozen 30 weight is a lot stiffer than frozen 5W20. But and maybe surprising is that 30 weight and 10W40 follow a pretty similar curve so the heavier multi-weights don't really improve on the very cold viscosity situation over the straight 30.

The other possibility is that the bypass valve is hung up. This could be a spring problem or the valve is physically restricted from opening the bypass hole, this is usually caused by a burr left when the bypass hole was drilled that catches the valve shuttle.

Bogie

[69chevyLWB]

Temp was in a heated shop kept constantly at 55F. never inspected relief spring in oil pump just looked at the roll pin that was installed so that the spring couldnt be tampered with. screw on filter also is stock style that has bypass in it. should i pull the pan and look at the pump and inspect or continue with break in?