what is a good oil pressure for a 1985 305 engine?

 

10 PSI per 1000 RPM

 

I second that!

 

10 psi / 1000 RPM is the rule of thumb for "acceptable" performance usage. It is considered adequate for survival.

Stock, fully up to temp, with normal oil (10W-30), these cars make about 20-25 idling and 50ish cruising. A replacement oil pump may only go to 40ish cruising, which is still fine.

 

mine only gets to 30 cruising. Is that bad?

 

Not necessarily.

 

Right...

What is it idling, hot?

If it's 20ish, then it's fine; your oil pump's regulator spring just happens to be a little on the weak side of tolerance. Or perhaps, your motor has been rebuilt and they just used one of the "standard" pressure pumps.

If it's lower than that but stable and well-behaved, then your gauge might be wrong; in which case, most likely you might just need an oil pressure sending unit.

 

Well its never been rebuilt. And, when the motor is cold, it will idle at about 35 and if you rev the motor it will peg the guage above 60. But completely warm at like 220, it will idle below 30 and then hit 30 while stretching out the gears.

 

If this is with the factory dash oil pressure gage, it would be a good idea to hook up a mechanical gage and verify what you've got.