Freddie Two Bs

I have a stock '74 911. Today the oil pressure gauge started behaving funny. With the engine warm (190 degrees), at 3k RPM the gauge reads 60, with a very slight oscillation. Between 3k and 4k, the needle instead of rising steadily and smoothly it bounces back and forth in the range between 60 and 100, with fast oscillations. When I slow down to idle, the needle drops all the way to the bottom of the scale.

Can it be that the issue is just the gauge, or is there likely to be a problem with the oil pump?

Uwon

I don't know whether the '74 is like later cars which also has a low oil pressure idiot light. I presume that the idiot light, if present, turns off once the motor starts, in which case you do have at least some oil pressure. The oil pressure gauge connection to the sensor at the motor is likely loose, or the sensor is malfunctioning. I think that your sensor is located just below the fan to the right of the crank. It looks like a small round can with the connection on top.
Good luck.
Johan

no.radar

On a later model 911, I had exactly those symptoms, and it turned out the electrical grounding strap was badly corroded. Simple cleaning immediately fixed the problem.

Good luck.