I have a 74 1.8lt and I did a tune up today because my oil pressure light keep coming on after five minutes of driving. So we change the oil and filter, spark plugs,valve cover gaskets. We put a 10-40 oil. today was a cool day so the oil pressure light came on after about 15-20 minutes of driving. what could it be? Should I go with a heavier oil or change the oil pump.

lets see could be three things off the top of my head, oil pump worn, oil pressure piston thingy, or main bearing. all three could cause it as it heats up and clearances open from expansion, i am sorry to mention the bearings

Thanks for the response! well I guest I am going to just have to drop the engine and get drity. I will check all three of those things out and see what happens. I will post results.

I would get a mechanical oil pressure gauge and make sure that you don't have a problem with the sender before I dropped the motor.