I got a new GM crate ZZ383 engine. I got a bent pushrod, so I replaced new pushrods & rocker arms. Installed a 770 Holley and RPM Airgap. Turned it ON and this is what I see.

Well, when I first turn ON the cool engine, I see an oil pressure of about 60psi at idle. I drive the car and it initially stays at about 55-60psi. Once the car warms up while I'm driving for about 5 mins, the oil pressure drops to about 40-50psi while driving. When I'm at a stop light, it drops to about 20psi. I rev the car at the stop light, and it goes to about 40psi then back down to 20 psi. Street light turns green, I drive and the oil pressure goes back to 40-50psi during driving. Is this normal? When I let the engine cool, it does this all over again. Should the oil pressure fluctuate this much? I ask the experts.

Do I have some sort of leak (oil or vacuum)? Can someone please advise? Thank.

what weight oil ya running, sounds about right just would like to see a bit more at warm idle.

I'm running 10W-30 and get pretty much the exact same behavior as the original poster -- I was about to ask the exact same question! :)

- John...

you will drop a bit as the oil gets hot, ive always ran a single viscosity, like a straight 40, this isnt a winter driver right?

You are well within the specs for GM. 20 psi at idle hot is fine. I 'believe' GM wants a minimum of 10 at idle and then 10 for each 1k rpms after that. So 20 at 2000 rpm is within spec.

gm also specs that burning 1 qt. per thousand is ok but i wouldnt want that either

I too was a bit freaked when my oil preassure dropped to 15-20 psi during idle, only to be told by my mechanic that is normal for a 600-800 rpm idle run on a 350. (I most always shift to neutral during stops to keep it up). Another factor involves oil technology - the newer lighter weight multi vescosity oils in stores todays are mostly designed for smaller and higher revving, tight tolerance engines. Small size import engines are perfect examples. The older design, larger displacement engines like we involve ourselves with (oh yea!) are better off with single viscosity, 30 or 40. If you are mind set on multiweights, go with 20/50.

I have same engine waiting to put it. How did you get a bent pushrod and how does it run?

I agree with az, go with a thicker oil at least 10-40!!! i use valvoline 20-50 racing oil in my 383 i have had it for 6 years and still get 60lbs at running speed and 30 at idle corse it idles at about 1000 rpm big meaty cam and all!!i use 10-30 valvoline in it in winter just for start ups and keep fluids moving dont acctually drive it in winter! just my 2cents

15/40 Diesel oil is perfect for a old Big Block engine.It has zinc and a few other goodies still in it that have been taken out of passenger engine grade oils dew to the use of cat converters.

Thanks guys, I feel allot better about my oil pressure. I was getting scared for a second. To answer some questions, I'm running 10W-30. The GM spec sheets says to run 10W-30 when you break in the engine, so I did. I'm sticking with 10W-30 for about 10,000 miles, then I'm changing to synthetic oil.

How did I get a bent push rod on a brand new engine, you ask? I don't know!!! That's what I said. I followed exactly what the GM spec sheet said to break in an engine. My #2 intake pushrod was bent and my #2 exhaust/#1 intake pushrod where off the lifter. Went to a GM dealer for warranty work and they said that I had to allocate $2000. They said that they had to open the engine up to see what causes the bent pushrod or if anything else is damaged. Then they call GM and tell them their analysis. GM will determine if what caused the bent pushrod is under warranty. So if GM says its under warranty, they pay for the service. If GM says that it was something I did that caused the bent pushrod (which they most likey will since I installed it myself), I have to pay for the engine work that has been done, fixed, then installed back into the car. Therefore, the $2000. I said "Screw That!!". I fixed it myself. I decided not to go with the warranty work because what stops GM from saying that I didn't break in the engine right, then get stuck paying $2000 for them to fix + the price I paid for a brand new crate engine. Now way!!!

did you set the adjustment on the valves or did it come that way? Im not sure what cam or who installed it but im guessing that all came installed and the clearances and cam timing should have been right, plus youd have more problems than a bend pushrod if they were off. But maybe when ya adjusted the valves ya ran em down too tight?

You let GMPP off the hook. They will all try to get you to pay for the repairs GM, Ford, Dodge, and Toyota all of them. Once they look at it and see you didn't do anything to it they would of fixed it at no cost to you. Now that you did work on it your out of luck if something big happens to it. And it does not matter if you install the motor in the car most people that buy crate motors do and it doesn't void warranty.