My girlfriend got her motor rebuilt apparently by some backyard mechanics. It's an LT1 with a 1-year warranty. It only has maybe 20psi at idle and 30psi at 5000 rpm. I haven't dared to take it over 5000 rpm.

Anyway, what would cause the oil pressure not to build up with rpm's? How much oil pressure should a freshly built lt1 have at idle?

I know everybody is different. My friend Dave still has 40psi at warm idle and his lt1 has like 130,000 miles on it.

 

The 20 psi at idle doesn't really concern me.

Not building oil pressure as the RPMs increase could be caused by an oil pressure bleed down somewhere in the block. Possibly the press in lifter gallery plugs behind the cam gear.

When you're at 3000 RPM, and you tip in the throttle does the oil pressure drop? (pickup too close to bottom of pan, sucking the pan up).

Does the oil pressure just build to 30 psi and stay there? Sounds like the wrong pump and pickup.

I had an LT1 built which had the wrong pump and pickup. I had great oil pressure, but it would cavitate down to 20 psi at 4000+ RPM when I hammered it in 1st and 2nd, yet any other gear was fine.

Because the idle oil pressure seems to be fine, yet it just won't build pressure, I think there is an issue with the pump OR the pickup is literally hanging onto the pump by a thread.

 

Try a 20-50 oil. A 10-30 may be to thin for the clearances.

 

No doubt that is a good idea. It sure helped in my case.

However, not actually building oil pressure normally with thinner oil, indicates a larger problem.

 

Now my trans am is doing the same thing as my girlfriend's car. well, at least, i just noticed it is.

When I slam the gas from a dead stop or a slow roll, the pressure goes no higher than 30psi at 6000rpm.

When I just tap the gas when it's out of gear, it jumps up to 40-50psi at 5000rpm.

when it's cold, it will climb to 70psi at 6000rpm.

And sometimes, even when it's warm, it will hold 40psi while crusing at 2300rpm.

Also, sometimes when I am in gear and I slip the clutch a little to make it bark, the pressure jumps dramatically up.


Btw, does synthetic oil build pressure better than regular oil?

Also, this motor was built loose for a 300-shot of nitrous. would this explain the relatively low oil pressure? Then again, wouldn't it be a bad idea to have 40psi while spraying a 300-shot? Then again, would spraying nitrous increase the oil pressure?

 

Get some decent oil in those cars.

 

The guy I bought the motor from requested that I use 15-50 synthetic. But it was about the same with that.

What do the numbers mean? I also that the number with the w beside stood for winter weight. and the number to the right stood for summer weight.

 

The 15 is the cold oil weight and the 50 is the hot oil weight.
That is what it's supposed to flow like cold/hot.I'm old school and never did like synthetic even though I use it on some.
I use Kendall GT1 50W in all my circle track engines and never lost a brg or had any failures in 30+ years
it's a personal preference from that.

 

It sounds like a few people have the wrong pump/pickup and possibly the wrong height of the pickup, and/or no stock windage tray.

Time to drop those oil pans and check. It is not fun, but it solved it COMPLETELY for me.

 

I do know for a fact that I"m running a stock oil pan.

 

Does GM have a factory rated WOT minimum pressure(or a 5k rpm minimum I guess)? I've seen the 6psi idle, 18 @2k, and 24 or whatever at 3k minimum ratings but what about WOT?

I've also only got around 35ish psi at WOT when fully warmed up (15-18ish idle, 10w30 dino oil) however I have none of the other inconsistent psi readings as the thread starter... Mine is definitely the original everything as far as the engine is concerned, 138k miles...