First off, I've got a 1985 L69 305 Carburated. Engine has 185,000 miles, still runs smooth, just burning a little oil through the valve seals on startup. Ever since I've had the car, the oil pressure will read about 30 psi on initial startup in the morning. Once the engine reaches full operating temperature, the pressure drops to about 10 psi. The pressure does not seem to increase with the idle speed. Should I be concerned with this(its been doing this for about 2 years) or does it just sound like a faulty guage/sending unit?

 

Start by verifying the pressure with a mechanical gage. You may just have a bad sending unit, or you may have a bad oil pump or engine.

 

It is normal for oil pressure at idle to drop as the engine warms up, because the oil also warms up and thins out, but verify whats going on with a mechanical guage, as Five7 pointed out.

 

Sorry if I sound ignorant, but where can i get a mechanical guage and how do I hook it up to my car? Thanks guys

 

Go to just about any parts store, they have them usually for pretty cheap ($10 or so). They just have a copper or nylon hose coming out the back of the guage, and a fitting on the other end that will thread into an oil passage in your engine. The best place to hook it up is where the oil pressure sender already is. That is either on the top/back of the block, below the distributor (look for a long copper T-fitting) or just above the oil filter on the block. Hook it up, use teflon tape on the threads so it doesn't leak, and then start it up and it should read your oil pressure right away.

 

It looks like my pressure sender is next to my dizzy. So I just take out the sender and screw in the fitting from the new guage?

 

On the back of the motor just to the right of the distributer there is a little brass bottle-looking part with one wire coming out of it. This is the pressure sender.

I'm not sure if anyone sells an oil pressure tester, but this is how you can build one.

You will need a pipe nipple and a gage that can read at least 60 psi, your local hardware store or plumbing supply should have these. The nipple should be 1/8th pipe thread, 3 or 4 inches long, gages are typically 1/4" you will need an adaptor coupling.

Unscrew the sender, screw in the nipple and gage and start the motor. The oil pressure will be displayed on the gage



(edit) Adam beat me to the punch, well hope this helps anyway.

 

Yes, just like that