I have a 1988 TransAm that me and my friend just put a 305 TPI that has approx. 30k miles on a rebuild in it. It has a flat tappet cam.

When I first start it when cold, it has great oil psi, up around 40-45 psi. However, after driving it around, when stopped at a light, it will drop down to near 5psi and it even showed zero psi tonight. I know that when the oil gets warmer it gets thinner and a drop in oil psi is normal, but zero psi is not.

The car has a new sending unit, it was converted to speed density so it has the sending unit above the oil filter. I always was told that on those cars, if the oil psi dips too low the ECM kills the engine, it isn't doing that now.

Car has the factory digital dash that works flawlessy as far as lighting up and all indicators working, but could the oil psi guage be taking a poop on me? The next step for me is an oil change to a thicker wieght, possibly 10w-40 to see if that helps. I'll get to look at the oil for any metal/water too. If it doesn't, then I guess the next step is a mechanical guage to see if the oil psi is really that low.

Anyone have any more input I can use to help solve this? We just put the engine in this car and I don't want to pull it again. It was a pain to get in. Just FYI, the engine was in my 88 camaro i parted out, and it never dipped that low when in that car.

 

Hook up a mechanical guage and run the tube through the firewall... see what that guage reads compared to the one on the dash.