The oil pressure guage in my 78 decided to stop working. It just sits way up past the "80" in about the 3 oclock position. Could it be the gauge? the sender unit thingy? or something between them? It started acting up after I changed the oil or at least that's when I noticed it. Oil level is good and car runs fine. Any ideas on what to check out first before I spend money on a part that I may not need.
Thanks, Jeff

Make sure the wire didn't unhook from the sender. If it's grounding out  you might get a false reading.  Otherwise, the sending unit is the cheapest and easiest to replace first....

Is the sender that little thing on top behind the carb? Looks like it has a little rubber tube coming out one side.  Or should I be looking elsewhere for something with a wire?

It's the thing sticking out right above the oil filter. Kinda bell shaped.

Yep, that should be the pressure sender and the temp. sensor should be on the Passenger side with a wire going up to it from the starter area. aceinthehole2007-05-29 14:12:41

Found it and checked the wire, looks like a good connection. Is the sender a local friendly Chevy dealer, or Napa item?

If you disconnect the sender, does the gauge go down?
If you ground the wire to the sensor, does the gauge peg out?
If both of these "tests" make the gauge peg in both directions, then the gauge and wiring itself is probably OK, and you need a sender...and yes, you can get one at yer local NAPA, or Chebby dealer.