The Stovebolt Site Forums The Shop Area Engine Shop OIl Pressure Problem Chev 350

I have just rebuilt a Chev 350 that ran on propane. It is now on Gas. I have had problems setting the lifters and have discouvered that once the engine warns up, I lose the oil pressure. I have replaced the oil pump and still have the same problem. i have pulled the intake and looked at the lifters and they look good.
Any ideas what could be causing it?

What is the oil preassure running cold vs hot? Did you make sure new cam bearings were installed?
Have you put a manual guage on to make sure the preassure is dropping?

OIl pressure cold was 18 or so at idle and once warm dropped to little or none. There was flow but no pressure when we disconnected the oil electronic sender unit. We then put on an oil sender unit where the oil goes up the tube and we can see the pressure from 0 to 60.
New cam bearings were installed.

Waggy,

Welcome to the Stovebolt. I'm not sure I understand your last post. You need to put a known good mechanical gauge on the system to get a bullet proof reading of your oil pressure...you want to bypass any questions with a sending unit or electrical gauge.

If your mechanical gauge verifies the cold pressure at 18lbs, you have a problem. It should be much much more than this, and with a new engine, should drop very little when warm.

If all your rebuild clearances were proper then the assumptions would be; the pump isn't picking the oil up or there is a massive internal leak somewhere. I don't think this much pressure/volume would be lost in the lifter area without some other telltale rattling or banging. You said you changed oil pumps...did you remove a new one and reinstall another new one. Do they come with the pickup tube installed? I don't know if a loose pickup could draw air and result in diminished oil flow.

Oil that has been thinned by fuel from a leaking fuel pump won't develop as much pressure as good oil...does your oil smell of gas or seem extremely thin?

Stuart

I agree it would have to be a very massive internal leak to cause that low of pressure on start up. Or could the pickup tube for the pump be partially clogged or too close to the pan bottom?

If bearing clearances were too great, looks like something would be making noise. Does this engine have an external oil cooler? If not, look at the adapter for the spin on oil filter and make sure the relief valve and spring are still in place.

Check the main bearings to see if perhaps a bearing half might be missing. It still looks to me like it would make noise without one shell in place, but it might not. But with one shell missing it wouldn't pressure up very well.

Good luck in your hunting and let us know what you find.

Did you simply pull a valve cover and see if its oiling good and oil going down the returns? Did you put in a "beefed up" oil pump that may be sucking the pan dry. Pumping oil faster than it can return??
Keep us posted.

I had a problem on mine, the oil pickup was too high(you could move it by hand) was sucking air with the pan full.

sounds like it is either drawin too fast or the pickup is too high as Gazim said .

I have replaced the lifters and the poblem appears to be gone. I had tightened the rockets to tight and the lifters no longer lift!

Thanks for everyones help. I did test most of the ideas, and have stored them away for next time!