Hello,
I have a low oil pressure problem on my 1993 K1500 Silverado, ext cab. with 350cid engine, 4L60E trans. I did a full rebuild on the motor 3 years or about 30000 miles ago. The oil pressure is low when engine is fully warmed up and at idle, trans in gear. If not in gear the slightly higher revs keeps the oil pressure more or less ok. With engine anything above idle the oil pressure is fine. Now this was my first time doing a complete rebuild so when the machine shop told me that the main journals were a couple thousands too big I did not ask enough Questions. Anyway when I plastigauged the mains they were at 3 to 3.5 thousands clearance which was at about max for clearance and just had to go with it. I run full synthetic 10w40 oil with half a bottle of Lucas Oil zinc. The synthetic does better then convention oil. I guess because it flows better. My Question is what can I do about this? Will other oil additives help? Could/Can I order main bearings that are 8 under instead of 10 under (the crank was ground 10 under). I guess I could run heavier oil in the summer?? Any thoughts would be much appreciated!
Chris Erhard.

 

oil pressure on these engine can drop after some miles have been on, what do you consider to be "low"
The rule of thumb is that you need to maintain 10 PSI of oil pressure per 1000 rpm on the engine. So idle oil pressure of 10-15 is fine

 

I have not put an external gauge on it. But low enough for the light to come on.