Just out of curiousity, what is the oil pressure reading supposed to be at idle on a 1991 Z28 with a 350cid?

 

Well, I have an 89 GTA with the 350 TPI motor and (when warmed up) the oil pressure sits at about 18 to 20 psi I believe. Obviously, when cold it is higher (about 38-40) and drops as the oil warms up. Basically you'll be ok as long as it is over 12 or 15 when warm.

BTW, this is just observation, if anyone thinks I don't know what I am talking about feel free to say so.

 

They say an engine needs about 10psi per 1000rpm.....but I wouldn't trust anything that idled at less than 15psi warm. Mine keeps about 20psi on the not-so-accurate stock gauge.

 

After installing a autometer mechanical gauge on my 91 formula 350, I found the factory gauge to be somewhat optimistic in its reading, and at idle I actually had about 20lbs when hot, as compared to the factory gauge reading about 30lbs. Thats with 10w40 mineral oil.

 

Currently my ambient temp is around 60 and my pressure according to the gauge is about 30 psi