Classic/Antique Car Repair: no oil pressure, oil pressure gauge, plymouth barracuda

Question
Mr. Benjamin;  thanks for the quick response to my question.  I think that I'll pull the oil pan off and just replace the pump, since it's got a lot of miles on it anyway. The noise I hear is not like a rod knocking, but sounds like lifter rattle; you know, the sound you hear from a high mileage engine before it picks up the oil.  I'm a grade B mechanic that hasn't worked professionally in the field for over ten years, so I appreciate the help that I sometimes need.-------------------------
Followup To
Question -
My '74 Plymouth Barracuda has been sitting for several years.  Though it hasn't been driven, I've started it from time to time.  Now when I start it, there is no oil pressure reading on the gauge and the engine is noisy, so I think that the pump is not working.  I slightly overfilled the engine with oil and restarted, but that didn't help.  If possible, how can I reestablish oil pressure.  
Answer -
This is a very serious problem - most likely the oil pump drive has failed.  The engine will be severly damaged with only a few minutes of running without oil pressure.  You'll need to have the car towed to a mechanic, and the mechanic will have to investigate the oil pump. If you ran it long enough that you heard noise, chances are very good that you are in for a major engine rebuild at this point.  

I'm sorry to be the bearer of bad news, but I think this is the situation.

If you had not heard noise, I would have said that your oil pressure gauge might have failed, but the noise symptom is pretty definite evidence of metal to metal contact - bad news!

Sorry,

Dick

Answer
Yes, I assumed what you were hearing was lifters clacking.  Those are the first things to sound off when the oil pressure drops so low that the oil doesn't make its way up to the gallery that feeds oil to the lifters.

Your pump might be OK, but the drive shaft that runs down to the pump from the bottom of the distributor might be sheared off - that is the more likely failure, especially if you have heavy oil or STP in the engine, and the weather was cold when you tried to start it.  If the oil is really thick, the shaft will shear off so the pump doesn't turn with the distributor.

Dick