I have a 1995 mustang gt. Just put all new gaskets on the block and got it in. It runs okay but my oil pressure gauge is maxed out. Theres a L and an H for high and low on the cluster and it goes past the H all the way. My battery in the picture is reading low volts bc it hasn't had a belt on it just been getting it in time and taking it apart again. Any ideas why is so high?
Also the car idles at 1k to 2k. and when you rev it and it goes to idle back down it stops 1.5k
The oil pressure gauge on our car is a glorified idiot-light, it show L if you have <~6psi oil pressure, and somewhere midrange if you have >~6psi oil pressure. Your sending unit (near the oil filter) might be shorted to ground internally, you may have a wiring problem (make sure all of those grounds are reconnected), or you may have a gauge problem. If I had to guess, it's a wiring issue after an engine installation. As you're running with no alternator and low voltage, you'll want to get that remedied before worrying about the gauges. They're prone to acting up when voltages aren't what they're supposed to be.
I will go check for all my grounds again and see if I find anything. I am getting my battery recharged today. Hopefully it solves its self it's been sitting for 3 months. And I had the battery recharged once