I want to start off saying that I have done anything and everything to build up more oil pressure in my 1997 3800 Firebird. I have changed the oil pump and the timing cover. I have also changed the pressure relief spring, and I have also change the sending unit. When the car starts up it runs a good solid 60 lb and then driving around for 15 minutes it will run about 25 lb around town and then at a stoplight or at idle it gets all the way down into the red. I have hooked up a manual gauge and at hot idle it runs about 4 to 5 lb. Does anyone has a clue of what it could be?

 

How many miles are on the engine?
It may be that it's just worn out and needs a rebuild,main bearings may be about gone.

 

I do not know how many miles are on this engine, I found remanufactured heat tags on the back of the block, and when I bought it the kid said his dad put in a new crankshaft and then it was locked up, so I took the engine out and found out that they put in oversized bearings in the connecting rods, so I changed that but I didn't look at the main bearings

 

To track this down you would need to check all clearances in the motor. Sorry no tricks or shortcuts on this one. Mains and cam bearings are the most likely. How much clearance was in the rod bearings?(I am guessing Zero) How much do you have with the new bearings? I assume if he put in oversize bearings he did have the the rods resized he just got the wrong bearings? Are the mains the right size? While the engine was tight was it tuned over at all?

Is there any metal in the motor or inside the filter? Have you run the car without a valve cover on? Are you getting any flow to the rockers? At that low of an oil pressure the valves should be having a clapping party. What is the oil pressure hot at 1000 RPMs? I have seen 3800 that idle really low, so low the oil pump and alternator don't work right.

Next based on mileage and history how much time and money do you want to put in this motor? You can buy a very low miles 3800 out of a newer FWD car for under $500. If the issue is Main bearing or Cam bearing it will cost you more than that to fix correctly.

 

The guy before me had put in oversized bearings in the rods because the engine wouldn't even roll over. He put .10 size in and I checked to see what the size of the crankshaft was and all I found was a marking that was "ss", which I assume is standard size. I unfortunately didn't check the main bearings to see what size they were. I was just trying to get the thing to turn over. I do hear chattering at idle, assuming that there is not enough oil pressure to get up to the rockers. I think I'm going to try to change the main bearings, because when I bought it the kid acted like that's all his dad messed with was putting in a new crank, so I think that's the problem with the motor. if that doesn't work I have a other engine I can pull from a camaro. I just really don't want to give up on the engine just yet, it look very clean on the the inside and out.