Am just putting the finishing touches on the new engine/tranny transplant on my 95 Z (forged 355 / built 4L60E). First fireup went smooth w/ 2 exceptions:

1) Oil pressure guage is permanently pegged at top of range, way above 80 psi, regardless of ignition on/off, engine running/not, battery connected/not. Any advice? Please don't tell me I have to replace the whole damn cluster...

2) Temp guage doesn't work. Maybe I forgot to connect the harness to the sensor? Is it the one next to the spark plugs on the LH cylinder head?

Thanks guys

 

Both issues sound like you didn't plug everything back in. The oil pressure sensor is on the top back of the block on the driver's side. Temp gauge plugs into the driver's side head between #1 and #3 spark plugs.

 

Sounds like you either broke (most likely) or left the oil pressure sensor disconnected. It's on the back of the intake, connector towards the driver side. Very easy to break especially while doing an engine swap. It may be disconnected too. Same goes for the coolant sensor. Yes, the one that goes to the cluster is in the head.

 

BTW oil pressure sensor definitely is plugged in, and usually if not connected the guages will drop to zero, not max out.

 

Mine maxed out when it was broken.

 

A buddy of mine used a block out of a buick for his 355 build and it had a different oil pressure sensor.. slightly longer I believe. He experienced the same problem you are having so maybe you just have the wrong sensor!

 

On a 4th gen, the oil pressure gauge will peg if there is no connection to the sensor.

 

Another possibility is that you bent the pin inside the connector on the sensor. Take it out and look inside it.