Black01M6SS

iTrader: (3)

I've put around 200miles on my new 402 over the weekend. The oil pressure is concerning me a bit. On a cold start I have around 45psi and it seems fairly responsive to RPM changes. If I tap the throttle just a little it will jump up to 50-55psi. Sounds ok to me but the thing is as the car heats up the pressure drops off a pretty good bit. After driving 30 minutes or so I will have around 25psi at idle and it will only climp to 40-45psi at 5000rpms. Fairly unresponsive to rpm change

It has an SLP high volume oil pump in it. The pump only has around 1500miles on it. I put the oil pump, pick up tube, and oil pan on while the engine was on an engine stand so I'm sure the O-ring isn't pinched. I did reuse the old one though...it looked fine so I didn't think it would be a problem.

So do you guys think this is normal? If not do you think it is a sending unit problem or should I have not reused that O-ring on the pick up tube?

Tony Mamo @ AFR

iTrader: (13)

Your bearing clearances are likely on the generous side....I would do some data logging with it and see if it maintains around 10 PSI per thousand RPM's. Honestly WOT at say 50 PSI is probably adequate but if the engine was built to normal spec it would see at least 10 per thousand, especially with a larger pump. I doubt its the O-Ring because everything sounds like its working the way it should. Some engine builders prefer larger tolerances on the bearings....I would get with who built it and see what they have to say. In the event you have a problem speaking up now is probably a good thing.

Good luck,
Tony

Black01M6SS

iTrader: (3)

Hmm...the shortblock was built by TSP. I quickly reved it to around 5500 today after it was hot and it was only at ~45psi. I think I'll replace the sending unit and change the oil then do some logs. I want to make sure that the readings I'm getting are good before I start questioning the engine builder on his work.

If replacing the sending unit doesn't change anything and I find out the clearances are on the generous side...could I just add another shim to the oil pump to up the pressure a bit?

Black01M6SS

iTrader: (3)

I bought a new oil pressure sending unit today. Probably won't change anything but I want to make sure the readings I'm getting are correct before I start going over everything else.

Any chance the GM Engine Oil Suppliment thinned out the oil? Someone mentioned it in a post I read when I searched the topic. I used Valvoline VR-1 SAE30 because no one had the 10w-30. I'm just wondering if any of this could effect it.

The oil pressure doesn't seem dangerously low or anything. I would just feel more comfortable with it higher. When I left the house this morning it was 45psi at idle and 60psi by 3500rpm...but after my 15 minute drive home in the 5PM heat it was around 30psi at idle. I'm not brave enough to rev it to 6k but I don't think it would climb up to 60psi after its good and hot.

OUTLAWZ RACING

iTrader: (9)

The thicker oil will show a higher psi because it takes more pressure to push it. I wont sweat it i used differnt oil in my strocker and the psi always change. i use to use Q 20 50 and hot i will see 45 psi cold its at 65, wot 80 psi. I now use 0 w 40 mobile and hot its 40 psi and cold its 55 and wot its 75 to 80 depending on how hot the turbo is. Oil will play a good part in psi I wont sweat it unless your losing psi everytime you dive your car then I would be concern.