Thread: 402 oil pressure

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We just completed a rebuild on a 402 Chevy. Comp roller cam and rocker arms, ported heads and 10.5 pistons. We had the engine on a dyno producing 483 hp and 482 torgue. The oil pressure was at 75psi. We have driven the truck about 10 miles and did not exceed 3000rpm. The oil pressure has dropped to 30 psi and has a squealing noise. Any suggestions?

Find the squealing noise, as long as you have oil pressure should be ok, things are getting lubed, oil pressure will fluctuate when motor comes to temp and as oil ages.

take the belts off to make sure that the squealing isn't in the accessories--they probably weren't on the dyno

Originally Posted by angrystroker

Find the squealing noise, as long as you have oil pressure should be ok, things are getting lubed, oil pressure will fluctuate when motor comes to temp and as oil ages.

I agree, other than the squealing noise you're OK. My SBF stroker did much the same thing - pre-lube pressure of 65 to 70psig, but after it ran a while I get just below 50psig on a cold start, dropping to around 35psig hot, idling down to about 15psig. The guy who built the engine says not to worry about it.

Edit - One thing I'd do is verify your timing. Retarded spark will drop your pressure.

Oil over full?

The squeak is the single V belt driving the alternator. After the truck set for an hour, I started it up and had 60 psi oil pressure and after warming up it has 40 psi. Every thing must be ok, just nervous on start up.
Thank you for your replies and Merry Christmas.