Mechanics

CHEVY NEW ENGINE DEVELOPED LOW OIL PRESSURE

1984 Chevrolet Blazer

Drive Train Axles Bearings problem
1984 Chevy Blazer V8 Four Wheel Drive Automatic 7000 miles

I replaced my engine with a crate small block 350 about 5 months ago. 194 heads, flat top pistons, rv cam, dual chain timing. It ran fine up until about 3 weeks ago when the oil pressure started fluctuating. It dropped way low at rpms lower than 2000 after engine gets to normal operating temperature. I had used the old oil pump on the new engine and figured that was it. I replaced the oil pump, used the old pickup screen and tube but noticed some cork and silicone debris in the screen area. Now it's better but the same problem except it's below 1400 rpm.
I have 2 sending units. One behind the distrbutor which I replaced at engine swap, and one above oil filter that came from old engine.
I HAVE had a small oil leak I can't find. I'm thinking the front or rear of the intake as the rubber gaskets were squeezing out.
There was no o-ring to replace on the new oil pump (should there have been)?
I haven't heard any ticking noises indicating bearings, valves etc although my exhaust is a bit loud.
I bought a new guage so I can read exactly what the pressure is instead of relying on a 26 year old stock guage and I'm replacing the one used sender. I'm thinking maybe an o-ring between the oil pump and block got misplaced as well?
...any other ideas?


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Robhill1965
September 11, 2010.



What do you consider low oil pressure? Did you prime the old pump before you fire it up? At 2K rpm oil pressure should be around 40psi and at idle 10-12 psi.

Use a mechanical gauge and actually check the oil pressure and get rid of the old gauge

Rasmataz
Sep 11, 2010.
As I stated before, I got a new guage.

It's hydraulic and tapped in right behind the distributor. At hot idle (900 rpm), I have 12 to 13 psi and over 2000 rpm around 50 psi.

Cold idle I have around 50 psi and over 2000 rpm around 70 psi.

I am going to replace the oil pump again with a high flow pump, and while the pan is off, check my bearing clearances and look for any debri or scoring.

Tiny
Robhill1965
Sep 14, 2010.