I have a P1sc w/8psi on a 383 with 8.5 to 1 Compression. It has around 20 psi oil pressure at idle with 10w30 mobil 1 and comes up to 60psi at around 3000rpm. I have a canton pan.
If I am not under boost (disconnect belt) it will stay over 60 psi over 6500rpm and not drop at all. If I am under boost the oil pressure drops bad at around 4000rpm from 60psi down to 20psi. I have total seal (crap @ss) rings and I think I am getting blowby that is causing this but I am not sure. It is smoking under boost now and I am about ready to pull it and rering it.
Has anyone had this happen?
Lemme know please,
Botch

 

Hmmmm, your problem sounds almost exactly like my friends. His car was smoking underboost and he was getting blow-by. He has since then re-finged the pistons with some new ones and so far so good. This could be very well be your problem, what kin dof oil pump are you running?

 

That's what I was thinking/fearing

Oh well, I was wanting to get some more head work done anyhow.

I am running a melling h/v pump, I forget the p/n.

Thanks for the help,
Botch

 

How many miles are on your motor? What brand of rings would be suitable on a boosted motor?

 

I have the same problem, 5,000 rpm steady is no problem(65psi). But while under boost the oil pressure goes down. I have Speed pro moly rings. I think the problem might be more of oil not returning to the pan fast enough. Mine goes down to 30 psi under boost around 5,000 rpm. I broke in the motor for 5k then I was making about 6lbs of boost. I know the rings are good, my compresion check yielded 180psi. I have heard of NA guys with the same problem, could it be the oil not returning from the heads fast enough. I also use the MV55 pump if that helps.

 

Have you tested for the oil pressure loss in every gear? Is it the same. Trying to rule out the effects of acceleration.

What pickup are you running?

 

Does your canton pan have anything in it to keep oil from climbing back of pan when under acceleration? If not it may not be boost but the rate of acceleration under boost and no boost. Miloden or Moroso sells a plate that you bolt between the pump and block and then trim to fit your pan. Thats what I have on my car with the stock pan.

 

I have the stock pan, but I seen others on here that have the same problem, I am not sure if the machine shop shop reinstalled the factory baffel or not. I dont know if the oil is climbing the back of the pan or if its just all ending up in the back of the heads and valvecovers. I have been told that as long as I dont get below 30psi its not too bad especially if it goes right back up when I let off.

 

The pan is baffled, has a windage tray, and scraper. It loses pressure under boost even if you are spinning the tires. It still smokes under boost too. The motor has 7,000 miles on it.
Thanks for the replies everyone,
Botch

 

Hey I missed the smoking part the first time, sounds like we have different problems. Have you done a compression test on it lately?

 

Did you ever fix this prob? Im having the SAME PROB N/A though... Don't even wanna think about spraying on it...

Look at my topic HERE tell me if your having the same problems.

BTW: Does yours do this at a DEAD STOP? Or in idle for that matter... Cause if Im moving, or sitting still, as long as I put it in neutral, I can rev the motor as high as I want and hold it, and the pressure will NEVER drop

 

I posted about this in the LT1 forum, I think the melling sucks the pan dry under accerlation. I may think about getting another pan.

 

I have the same problem, but am Not blown, yet - D1 on the way.
I found the oil is foaming at high rpm under acceleration. Lower your oil level 1/2 to 1 quart, and your problems will go away.

 

I had a chance to work on it some today and found out some interesting things. I have good compression(175-180) and leakdown is very good as it should be with total seal rings (less than 5%)on all cylinders. The spark plugs showed something interesting though. The #3 and #6 plugs look to be running very lean and the rest are running rich. I am running a evacuation system on the motor and am wondering if I have an intake manifold gasket blown out on the lifter valley side. That would cause the oil to get trapped in the valve covers, which would starve the pump and send oil into my evacuation system and make it smoke under boost.
I guess I'll pull the intake and see if I find anything. I'll keep you posted on the results. Any input is always welcome.
Later,
Botch

 

WOW that's an intresting theory... Ill have to give it a try and see if that works...