Oil Pressure question
 

The crate engine in my '79has about 800miles on it, and about 200 ago, it got its first oil change. I drove it to Bowling Green the day after the change. Everything seemed fine going up, but on the way back I noticed that the oil pressure gauge was fluctuating. The pressure never really dropped substantially, but the gauge went from about 50psi to 35psi about every 3 sec. or so. Any ideas?

BTW the first oil I used was Castrol GTX 10-W30 and the stuff I replaced it with was Mobil-1 10-W30 Synthetic Blend.

TIA,

Re: Oil Pressure question (e3pres)
 

ttt

Re: Oil Pressure question (e3pres)
 

Maybe the pick-up fell off the oil pump ?

It may not be that, however, the symptoms are the same.
I assumed you checked the oil.

Another thought, is the dipstick correct for that oil pan ?

Barry

Re: Oil Pressure question (e3pres)
 

Is the oil pressure gauge needle moving slowing up and down from 50 lbs. to 35 lbs. ? Or is moving very quickly between 50 and 35? If slowly, you may have some sort of mechaical problem. If quickly, suggest you may have a problem with your electrical/mechanical oil pressure gauge system.

Temporary installation of a mechanical oil pressure gauge will help tell you what you're dealing with. My oil pressure gauge needle 'bounces' some when idling, but maintains a constant reading when cruising.

Re: Oil Pressure question (e3pres)
 

This is probably not your problem, but I had a high volume oil pump in my 350/350 with a stock oil pan, and when I would cruise at about 80-85 mph my oil pressure would fluctuate like you were describing. I was told to replace my oil pump with a stock one or replace the oil pan with a bigger one to hold more oil. What was happening was at high rpm's the oil pump was pumping the oil faster than it would drain.