I had my 69 idleing while checking for a vac leak and walked around the bad and noticed the oil light was on. I cut it off and checked the oil and it was full. The engine sounded normal before I cut it off so I cranked it back up and the light stayed on again. So if a sending unit goes bad would it light up all the time or not at all? Or possibly either way?

Could be sending unit. Could be that the pump is losing pressure which would be really bad. If you're getting oil up to your rockers, it's likely the sending unit.

first thing i would do is put in an oil pressure gauge.by the time that light comes on,the damage is already done.that is assuming the sender is ok.

I bought a sending unit but didn't have a socket to change it. I cranked it and the light came on. When I rev it the light goes out but comes back on when the Rpms fall. That doesn't sound like a sending unit to me. But I would think it would be clacking or makeing some kind of different sound. This stock L48 350 has about 40k miles on it over the last 20 years since it was rebuilt.

Take the sender out and put an ohm meter between the terminal and the body. It should read nearly zero ohms. Then apply pressure to the port with regulated air pressure. Start at a low pressure and have a helper turn up the regulator while you monitor the meter. When the ohm meter reads O.L. or high resistance, you'll know what pressure the sender is tripping at.

Beyond this, you need an oil pressure gauge to test it before you risk damaging the motor.

Testing with a mech op gauge is what I would suggest.

Sending unit was bad. Thanks guys

Good to hear :thumbsup: