My oil pressure is real low, about 15 psi when cruising, 30-35 full throttle, and barely existant at idle. The only time the oil pressure is at a cofortable level is after sitting about 7-8 hours.

The engine is knocking at idle, so I know its not just my gauge.
I was just wanting your guy's opinion on the possible problems.
And I've decided to stop driving it until the problem is fixed, to prevent further damage.

And if I am to keep the car and need a engine rebuild how much would it cost? Its a 350 tpi in a 1987 firebird.

 

i just went through the same problem with my car all said and done ive got 1200 into the job including a new clutch, machine work, shop supplies, misc bolts..etc took maybe 50 hours including the port work, painting etc.

the engines been rebuilt on a small budget, hotter cam, heads ported, rebuilt carb. reused as much as possible. Just finished it tonight

I could of saved money if i bought a rebuild kit, but i bought parts a piece at a time when i had money so it cost me maybe 2-300 more, plus with shipping from the US they would rape me. Summit charged me 40 dollars to ship my cam, its free in the states

figure 700 if you do the work yourself and plan a little better than me

 

What oil are you using? If you're still using 5W30 just because that's what the filler cap reads, you need to ignore that and read the owner's manual. You can use much better oil than that at higher temperatures. I don't even use 5W-anything in -35° temperatures, let alone summer weather.

If you verify the oil pressure with a mechanical gauge, it may provide some more information - Even if you already "know" that the pressure is low.

There are a lot of possible reasons, from a bad oil filter to trashed crank and bearings. A pressure check might help discern between some of the possible problems.

 

The oil Im using is 10w30 Castrol Synthetic. And my oil filter was just replaced.

Im going to try to locate the knocking today using a hose or screwdriver, like sugested in other posts.

 

im having the same problem. funny thing is, is that im using the same oil as you and that caught my attention. not only due i have a deep knocking noise (during start-up and when i downshift) i also have a slight clicking noise while its idling. Thankfully my g/f's dad is the service manager at a local chevy/pontiac dealership so i took it up there on friday and found out that i blew out a main bearing and the deep knocking noise is my crank/rod and the clicking noise is a loose rocker. I'll admit that i brought it on myself by trying to show a nicely restored 68 camaro that it wasnt the only one that could spin its tires but now i screwed myself. im looking around at a lower rebuild kit or i might just get a LBC and re-use my cam and TPI. That is just to get me reliable again i still have "LS1" bouncing around my head but id rather get my car done in 2 months instead of like 5 or 6. Hopefully next year ill actually be able to sell the TPI/T-5 and get the LS1/T-56. If anyone knows some good places for a LBC 305 then id greatly appreciate it.