Oil Pressure

I have a 350 chevy in a pacer/crusader configuration. I rebuilt it and at low rpm's have little to no oil pressure. At 2000 to 2500 I run at 40 to 45 lb's. I am running 40 wieght oil as some one had suggested. I plan to yarn it out of the boat in the next week or so. Any and all ideas are welcome. Thanks guys.

Have you tried a mechanical guage at the engine? What is the warm, 1000rpm pressure?

Dave, I have both a mechanical and electric gauge, both read the same. I don't remember exactly what the reading is at 1000 but it is way way down. Sorry about the double post everyone, did not think the first one went through.

If the pressure is low enough at idle to trip a 7psi sensor, I'd say definately too low. If its still at least 10psi, I'd let it go, if that is the only symptom. Yes, a fix is likely either a main bearing job, or could be the pump. You might get some clues about the pump. What do you suppose the relief setting SHOULD be? BBC are normally 40, your SBC could have a higher set pressure. If the relief spring/plunger is stuck, you might expect too low psi at low rpm and too high at high rpm, plus likely a large change from cold to hot.
You rebuilt it. Did you measure the main bearing clearance with Plastigage? What was done at the rebuild?

ps; if a worn pump is in there, I'd expect a low pressure at all rpms, but building at higher rpms. Also, priming at starts might be slow.

We don't often see SBC total oil pump failure.
These are "Positive Displacement" type gear pumps.
Many are capable of producing 200/300 and up, psi.
The pump's internal relief valve is what controls the actual engine oil pressure. We can shim or change spring values, and come up with different pressures.

Agree with Dave...... if the relief is fouled up, this could be part of your issue.
If not, then you may have crankshaft/con-rod bearing clearance concerns..... even cam follower and/or camshaft bearing clearance issues.

While I hate to steer us away from the Marine forum format, some of the SBC Hot Rod forums are a good place to pose these types of questions!
These guys play with, and tweak these pump systems.

Ok guy's, help me out it's early. Define SBC. The pump is new and yes we did plastigauge the bearings. I would love to think it is the relief valve but until I get it pulled.....

missnancy said:

Ok guy's, help me out it's early. Define SBC. .............

Click to expand...

Small Block Chevy........as is your 350CID

As a last resort, before you pull it out you could try adding a couple of cans of STP engine treatment...STP is an oil thickener and if the relief valve is causing the problem, this could result in enough oil pressure to dis-lodge a stuck relief and maybe cure the problem...it's a long shot but there is nothing to lose.

Thanks Don, I guess this is where I say Duh! (-: Bobby, Thanks for the suggestion.