Originally Posted by 075turbo
What should the oil pressure be on a SBC 350?
I didn't have a gauge during cam break-in (I know, this was dumb).
After changing oil and filter last night after the break-in from Saturday, I installed an oil pressure gauge right behind the distributor.
After startup, it pumped up to about 35 psi and stayed there for our 10 minute ride that included periods of hard acceleration. Should it fluctuate with acceleration and/or idle or is a constant pressure normal?
A little background. It was purchased from a guy that had it in a street rod and said it wasn't fast enough for him so it only had a few hundred miles on it. A friend that has built several motors looked at the crank and cam bearings, cylinders, etc. and agreed. We replaced the heads after having a valve job and checking for cracks (smogger 882's), new cam, lifters and pushrods, salvaged Performer RPM manifold and new Holley 670 Street Avenger carb. Has the dish pistons with valve reliefs so I used the fel-pro 1094 0.015 head gaskets to get the squish down since the pistons were down in the block about 0.025. Compression is only probably about 8.25 to maybe 8.5:1
As always, I appreciate the help.
Unless your oil has the weight of water, even a stock Chevy oil pump should take cold idle oil pressure to the relief valve pop off which is 50-60 psi for regular production engines and 60-70 for production performance engines. This should drop to 25-35 psi at idle when the sump gets up to about coolant temp, that usually takes 10-15 minutes without a coolant warmed to oil heat exchanger. It should, with hot oil, still hit 50-60 for a production pump and 60-70 for a production performance pump as used in the 302 and original LT1 by 2 maybe 3 thousand RPM.
I'd suspect the gauge, or if electric the sender or system voltage to the sender, before I peel parts off the engine. Of course the other reasons for low oil pressure are to be found internally from excessive leakage on the pressure side from wide bearing clearances; or leaking galley plugs; or the distributor not installed correctly to where it opens the right side lifter galley to the sump. The other side of the coin on the pickup would be too much or too little distance between the pickup and pan allowing air to be sucked in with the oil, or the pickup so close to the pan bottom it can't feed; or the pickup tube leaking air at the pressed fit to the pump. Last would be with the relief valve itself having a weak control spring or the valve stuck open in the bypass configuration. And there's other things but these are the ones you usually find.
Too bad about the pistons, chambers and compression, or rather lack there of. This is a long way from an efficient and effective set up that's costing power not developed for the excessive fuel burned.