I just put new heads with new rockers, pushrods, springs, exhaust, and carb on my car and it makes an annoying hum at all rpms, in park and seems to be worse under load in drive. Its real loud. I thought I remember reading once that it could be faulty lifters? Only 4 of my lifters had any sponginess to them when I preloaded them, I really had to wrench down on them to get em to move, but I made sure that they were adjusted right. Could this be the problem, or a problem? Could they not be filling with oil and just half-seizing? I ran the car with open headers at first and the hum is the same with mufflers on. Here's another thing, my oil pressure gauge burys itself when I havent ran the car for a while, and now it seems stuck at 30 with the key off, yet when I rev it, it does fluctuate and sometimes drops below the "stuck" 30. ???? Any help is greatly appreciated, I never wouldve gotten this motor together if it wasnt for this board!

 

Sounds like you got two problems..first one ..did you remove the belt and start the engine and notice if it hummed again.If it does then yes it could be in the motor itself(I have never heard a lifter hum,tick.. yes,but never hum)if it doesnt hum then you have a water pump bearing/alt.bearing/power steering etc going out.
As far as the oil gauge this is an electrical circuit ...I would make sure you have good oil pressure and install a manual gauge and see what the reading is(better to be safe).Maybe replace the sending unit and go from there.If the sending unit doesnt help it might be in the gauge itself.good luck