I just completed a valve stem oil seal replacement job on my 1977 350 SBC. I was very careful during the job to guard against letting any debris from getting into the motor. I had all the oil drain holes plugged and completely cleaned the top of the heads. I also performed the rework according to the “book”, and the motor sounds and runs very nice following the work. However, during the initial test drive I found that the oil pressure gauge holds steady at 40psi (which was the norm before the work) until the motor reaches 1500rpm, then it immediately pegs out at or beyond 80 psi. When I back the rpm’s down to 1500rpm or below the gauge comes back to 40 psi. I also see that when the car is turned off the gauge stays at 40psi (does not return to "0") as it should until the ignition switch is put into the on position (not running just switch on) at which time the gauge returns to normal “0”. This leads me to think it’s an electrical issue rather than a true oil pressure issue? Possibly I hit a wire or connector during the work that has led to a bad ground or something?

 

Welcome to the forum. If you have a mechanical oil pressure gauge, then you need to put a gauge on the engine itself and see what the pressure is doing. If you have an electrical oil pressure gauge, then you need to check the sensor and make sure that the wiring and grounding is good.