Mechanics

WEIRD OIL PRESSURE IN A 400 SMALL BLOCK CHE

1976 GMC Sierra

Engine Mechanical problem
1976 GMC Sierra V8 Four Wheel Drive Automatic 00000 miles

I have a 400 ci small block chevy in my car and the oil pressure is acting strange, I installed a cam (used correct breakin lube and primed the oil system) and broke it in for the sugested time and rpm, and when the time was up I had very low oil pressure (15-20psi at about 2250rpm) I turned the idle down and the psi was lower yet so I shut it down. I repulled the engine and replaced the rod/main bearings and crank. After I got it all back together I started it up and it had good oil pressure, around 50 or so cold, but when it gets warm and your at a cruise and speed up to around 3000 rpm the oil pressure drops off, from about 40 to 15-20. If you are low a quart this will happen at a lower rpm. It seems like the oil is not gettin back to the pickup somehow, or would bad cam bearings cause this, or is there something wrong with the oil pump? Why would have this happened in the first place, I have never had a problem breaking in a cam before or since.
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Justin1965
April 16, 2008.




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