1989 corvette with 150,000 miles oil pressure?

[Anthony B]

I have an intake manifold gasket leak and valve cover gasket leak... running 10w40 the car at crank up will read 45 psi oil pressure and after warming up and driving for a few minutes it will drop down to 19-24 at about 700 rpms at about 200 degrees the cars timing is slightly off and I need to adjust that it will cause somewhat of a miss no weird loud noises just a lag for a second doesnt burn oil or anything what so ever I am going to adjust the timing in a week and fix the two leaks my questions are is the oil pressure bad????? down to 20 psi at idle? also with this car get 200,000 miles maybe before I have to do a rebuild? It has power and like I said it isnt burning oil or smoking out of the tail pipes at all?? If I put some money into it can I get 250,000 miles?
What I am wondering is 20 what the car should be running at ?? How can I find out I have tried googling the specs but cant seem to come up with anything... When I replace the valve cover gasket and intake manifold gasket with it raise it to about 25? Also I ordered a flame thrower exhaust kit what is the bad things about this?

 

[jumbobret]

20 psi is great after it warms up. The small block can run as little as 7 psi and be fine.

 

[steveg]

best way to check your engine is do what is known as a leak down test you'll need some special equip. but is a good way to check another way to to do a compression test which is easily done with with equip. from local auto store be sure to remove all spark plugs, pedal to the floor while turning eng. over also keep wires away from cylinder ex. to keep from a fire hazard