Big Problem! Help!!!

ALright I got a 95 firebird 3.4l with a 5 spd and when cold at idle the pressure reads a healthy 38lbs, when it gets hot...around 200 deg F at idle the OP reads a whopping 10 lbs. After dealing with this for awhile I changed the oil and filter...nothing...then I put a manual gauge on it and it read 10 lbs..then I flushed the motor, changed the oil and filter...10 lbs. So now I was thinking the oil pump...now GM oil pumps usually dont go bad but the check ball has been know to stick open....so I pull the exhaust, starter, motor mounts, and pan and changed the oil pump...nothing was clogged in the screen but the check ball seemed a little weak. after swapping that I noticed that my thrust bearing was worn badley, so now im thinking bad bearings=bad oil pressure sooo I changed all the rod, main, and thrust bearings and put all the stuff back together. NOW heres were it gets weird, I started the engine up and the oil filter seal immediatly pops. I replaced it and tightened it more...tried again...pops. So now I thought maybe im using too heavy oil for these new bearings so I put 5-20wt oil in and unplugged the coils. I turned it over for awhile to get everything primed, plugged in the coils n thried it again......80 psi!!! Woa somthings wrong, I waited for awhile till it got hot and the pressure steadily dropped to...you guessed it....10 psi. What is goin on here!? Maybe the cam bearings are bad? If so why the high oil pressure when the engine was cold!!??? Maybe I got another bad oil pump? PLease help! I cant get to work I live 45 min away from my job! Any thoughts!!??

You have done so many things that I would have done . I think the only thing left would be the rod pins in the piston and the lifters . Sounds like either the oil is getting too thin or getting thru a gap after metal expansion from heat . I have a blazer with the 4.3 that does the same thing , just not down to ten PSI .Mine ranges from 60 to 30 . If you had alot of play in the thrust bearing , that motion would wear the pins out . My TA w/LS1 holds 70 to 80 all the time . Rob

you need to check the bearing clearance. if the crank is worn you wont get any pressure when it heats up. get some plastigauge put in your new, used whatever bearings and torque them down pull the caps off and use the gauge to determine you clearance. if its out of spec, you need to pull the motor and get a crank kit, if its in spec, don't ask me im out of ideas.

Another thing to look at. There's a little check valve uunder the filter. It can get clogged and hang up, or it can get weak and spew pressure. It's pressed into the block, and has a fibre plunger. You can push on the plunger. It shold offer SOME resistance, but not a whole lot. I have no spec on the spring tension.

The general description you offer SOUNDS like the relief valve (60 degree V6s use a spool valve like a Chevy V8, not a check ball like the Pontiac and Olds) is hung up. I would have insisted that to be the problem, had you not replaced the pump.

I agree with Light gray's assessment of checking the bearing clearances. Using PlastiGage works, but is not as accurate as a mic and bore guage.
Cam bearing can also cause this symptom. You must disassemble the engine to properly check them,.

Avoid crank kits unless your crank is damaged beyond reasonable repair. Regrinding your crank will maintain balance, and not subject you to the last guy's problems. Crank kit companies (such as Standard Crankshsafts in Charlotte) do their best, but as mass-production shops, they can and do miss things. We use kits ONLY when the original is not usable. A good crank guy will make yours better than when GM ground it.
If you DO get a "kit", make sure it's either 10/10 or 20/20 or any variation of those two. DO NOT accept one that's "standard/standard". That one has been welded on all journals. Cast crankshafts don't respond well to any welding.

Jim