65 GTO: 5654782 oil pressure sender and rally gauges; oil pressure often pegs
 

I swapped out the sender on my engine with the correct 5654782 NOS sending unit, and I have rally gauges. My oil pressure will sit at/above 60 upon startup and even after getting up to temp, its idling more in the 30-45 range. Is it really likely that the oil pressure is that high, or is there some wiring/connection that could be incorrect?

thanks!

What are you using for oil? If 20W-50, I would say yes.

After 57 years those gauges old GM can very easily go bad.


Either they read too high or not high enough. Once those loose their frame of reference the problem will only get worse.

First you should test the gauge separate from the sender to make sure it's reading true. I have seen old GM senders (after sitting for years) never on an engine nor pressurized be way off on calibration simply from internal corrosion. (Lack of use.)

There is no way that I know of to open one of those old senders up to clean and calibrate the electrics and then put the dome back to where it looks original.

Try an external gauge to see what it does

What Steve says.

Thanks all. I swapped another sender with this correct one to try to be “sure” my gauge would be correct, but I think the old sender was more accurate. I’ll try another modern sender to see if I get significantly different readings. Engine runs fine and plenty of lube on top end so I don’t believe I have any issues.

I'd do a temporary install of a mechanical oil pressure gauge for testing purposes. If there is room, put a T in the oil pressure port on the engine and hook both the mechanical gauge and the electric sender up at the same time.

I think I have a spare mechanical, I’ll rig up a splitter to check it out.

Has your engine been rebuilt? If so do you know what oil pump it has? All my cars have more than 60 psig when started cold.

It was rebuilt when it was refurbed in the 90's, but unknown specs and mileage since then.