OP Mike
Do you retain an OE gage; one that might be rebuildable ?

 

What is that is failing with these gauges? Have you taken them apart to troubleshoot the issue?
You could probably buy a rebuilt original through an NCRS-type restorer.

 

Do you have a stock direct-reading oil pressure gauge (with oil pressure line feeding the mechanical gauge)? Or do you have and electric gauge, oil pressure sending unit on the engine block, and wiring between?
For a stock, mechanical gauge, they are VERY reliable and should last 50 years, if not damaged or over-pressured. The issues with this 'system' are related to the plastic (or metal) oil pressure line having a blockage and the fittings at each end sealing well.
For an electric gauge, they are also reliable. Although they can be damaged with power spikes or accidental electrical shorts. The issues with the electrical gauge system are the poor quality of aftermarket sending units and the potential for wiring/connector corrosion and/or wiring failures.

If you have the stock mechanical gauge, I would guess that you have a blockage/plug in your pressure line. There is no way to prove that or resolve that without opening up the center gauge bezel far enough to remove the line from the gauge. If you do that, you can also remove the other end of the line from its fitting, then blow thru the line to determine if there is a blockage problem. If it is resistant to allow air flow, then you need to clear the line by using some pressurized air (10-30 psi) to clear the line completely. I suggest that you blow FROM the gauge end of the line and TO the engine end to prevent splatter in your interior. This issue could have been your problem all along.

 

After losing some 5 -6 op gages over course of a few years / few thousand miles; perhaps the root cause isn't in either line or gage ?

Over-pressure was mentioned; perhaps the Bypass Valve inside Oil Pump is sticking open and permitting oil pressure spikes ?

Which, in turn and in & of itself, can cause gage failure.

 

The oem oil gauge was taken out probably 20 years ago and I did not think to save it,my bad

 

I'd suggest that if you are getting to this point, replacing the line is a prudent step unless you know for sure it is a relatively new replacement already. The plastic used in the oil line gets brittle with age and the last thing you want is to have it unknowingly snap when you're putting everything back together! Replacement line is cheap and pretty easy to route if you tie the new to the old and pull it through the firewall.

 

Hey Blue, some bad luck for sure. Sounds like you still have a mechanical type gauge and, if so, I would look in the FS parts section of the forum, or post a WTB, and purchase a OEM gauge from a forum member. The mechanical gauges are very reliable and (hopefully) you can trust a forum member - especially one who has been around for a while - to sell you a working gauge. You can get a new line/fittings from the forum vendors - I don't recommend reusing the old compression sleeves but that's just me.

The ammeter wasn't working on our '68 when we bought it. I didn't know what the problem was but purchased a used ammeter from a forum member several months ago. Finally got around to taking the gauges out a few weeks back and followed Ernie's instructions on how to check it. The one in the car checked bad, the one I bought from a forum member checked good - installed and and it works perfectly.

Your luck will change!

 

Thank you for your responses,I'll try answer your questions as to why I think it's just the gauges.One would read low when I had the engine built so after talking to the engine builder he suggested changing the gauge,that worked out perfectly giving me an acceptable pressure at idle(30 to 35 at idle,depending on hot or cold) and good at higher rpm,around 55 to 60 (stock oil pump) then (maybe a couple yrs,you lose track of time after awhile) the next one a couple years,the one after then it would stop at 35lbs no matter the rpms.the next one about a 1/2 to 3/4 mile then just stopped going up. I put an after market gauge in and it has worked perfectly for 2 or 3 years till I decided to put in another repro in dash ,which lasted 6 months and goes low at an idle(about 20psi) and only goes to 35psi at about 3000rpm's.Since it so easy to put the after market one under the dash I;ll do that this week to make sure it's the gauge.Thanks for the tip about blowing out the line but I've changed that but I'll do it again. It's a mechanical gauge. If I still have an issue I'll check the bypass valve.It just seems to me that a $20.00 aftermarket gauge could work so perfectly for so long without an issue and the repos fail so often. Once again ,thanks for you ideas. Mike

 

thanks that is one of my options,maybe I should do that anyway even if I go another route,can't hurt to have an extra gauge or two.Mike

 

One more thing,how do you tell a oem gauge from a repro?