oil pressure guage reading too high

[4v8s]

Hi all,

on my '77 firebird with the olds 403, the oil pressure seems too high but Im thinking it could be the guage not calibrated?

WHen I put the ignition on, it seems to reset to something like 20-30psi rather than at zero. When cold at idle its off the scale at 80psi, once warmed up at idle it sits about 45-50psi.

Is there a way of me checking this or adjusting the guage?

What I also notice is a similar thing on the coolant temp - seems to read too low and never gets to the middle of the guage.

Is there some sort of voltage regulator or bit of the wiring that could cause these guages to be off centre?

Thanks

[bhm1712]

Easiest thing to do first is to buy a new oil pressure sender which fits Above the oil filter, this might fix the issue and in any case will eliminate it from the fault finding either way.

They are cheap to buy and easy to fit. The gauge sounds like its receiving a voltage from the sender when there is no oil pressure

[SUPERCHARGEDGTA]

if you disconnect the wire from the sender it should go to zero with ignition on
if not gauge could be faulty (someone may have played with it or could just have gone off with age)
it is 35 years old after all

[bhm1712]

The plug at the oil pressure switch is easy to pull off, and if I remember rightly the oil filter adapter on a 403 is at the front so should be accessible from under the bonnet?