I noticed latly that my in dash oil pressure gauge is lower than my brothers is ( has a new 305 in a 85 Firebird ). Usually when I am driving it reads about 30( in the middle ) maybe a little more but sometimes At Idle it drops down to top of red and even a ways into red. I now this cant be good. I have 100k on the motor- think its finally time for a rebuild or do you guys think its something else. Also it runs very strong still.

 

Even new ones. Rod side clearance has a lot to do with it. If it comes up as soon as you touch the gas I would not worry about it.

10psi at idle is sufficent in most cases. You might get some rockers making noise but thats about it.

 

cool- thanks

 

Stock guages are prone to not being very accurate. If you are concerned, check it with a mechanical guage. I agree with what he said above 10 psi at idle and 10 psi for every 1000 rpm after that is plenty.

 

Oil pressure started to drop in mine like that just before the bearings went out on cylinder six. If you start hearing a slight knocking noise at idle and the oil pressure drops with every knock, you know your bearings have had it; clearance is getting too large from excessive wear. I owned mine for a little over a week before this happened. And I made the previous owner help me rebuild the dam thing...

 

if you want to be sure put a mechanical gauge on and check it. 10 psi for every 1000 rpm is accepted as "normal".

 

I had the same problem unitl recently; I suspected it wasn't my pressure when it started dropping down to about 0 at idle in gear. I changed the oil pressure sending unit and now my pressure looks where it should. Didn't get to double check it with a mechanical which I really want to do to see how the stock gauge fairs in the accuracy department.