I just swapped out a 2.8 out of my 89 firebird and replaced it with a 350 out of an 88 formula. I swapped the wiring harness and all components as well. I didn't disconnect any connectors off of the engine during the swap I just left the harness on the engine. Everything works fine after the swap except for the oil pressure gauge. When the key is off and at auxilliary the gauge reads "0". As soon as the car is started tyhe gauge goes to "80" and sometimes when driving will drop back to maybe "70" but usually stays at "80". Could the sending unit be bad or is it likely a wiring problem. The gauge worked with the old engine but I'm not sure about the old car. Like an idiot I didn't look before I ripped out the engine. Is the sending unit the same in a 5.7 and a 2.8 so I could swap to check that?

 

Heh the sending units are NOt the same nor are the guages. On the V8 cars the pressure guage read a max of 60 psi. try getting the right guage. Also it is possible that the pump in that engine was changed at some point and a high pressure/volume pump was installed.

 

Just install the sending unit from your 2.8L