I just installed an autometer c2 electric oil pressure guage and was wondering what a 302's oil pressure usually is at idle. And Also when I shut the car off the needle on the guage goes to 100psi and when I turn the car on the cage goes back down to the oil pressure while the motor is on which reads abou 50psi? I was thinking that I had a wire hooked up backwards but I'm not sure, any help would be appreciated.