[i82much]

I have the repop Rally gauges in my 65. My oil pressure gauge just kind of sits in in the middle of the range and doesn't move. I seem to recall that it started doing that after a cold start with 15w40 and really high (like 90 psi) oil pressure.

Can too much pressure kill the reproduction oil pressure gauges? If so, do you just have to run a thinner oil or avoid cold starts, or is there a workaround?

[Peter Serio]

Modern overseas copies of GM gauges are not made to the same quality standards as the original USA made parts.

They use cheaper plastics and/or nylon and thinner wire to wind the electromagnet. Those new gauges can be off by at much as 15 to 20%. You have to keep in mind that all of these parts have come 1/2 way around the globe just to get here. So anything heavy is a no no. Lighter, faster, cheaper, thinner and simpler are the watchwords. The best thing to do is have that gauge tested using the sender, jumper wires and a 12 volt battery. I use air pressure with the sender to test. Wire it up the same way it would be in a car. Thread on the sender and feed in compressed air with an accurate gauge on the air pressure and compare readings. The photos below are from the year 2003. Here I am testing an original DELCO 1970 Buick GS oil pressure sender using an ohmmeter and my compressor. But I prefer a direct wire test using a 12 volt battery if the dash gauge is in question.

[i82much]

Originally Posted by Peter Serio

Modern overseas copies of GM gauges are not made to the same quality standards as the original USA made parts.

They use cheaper plastics and/or nylon and thinner wire to wind the electromagnet. Those new gauges can be off by at much as 15 to 20%. You have to keep in mind that all of these parts have come 1/2 way around the globe just to get here. So anything heavy is a no no. Lighter, faster, cheaper, thinner and simpler are the watchwords. The best thing to do is have that gauge tested using the sender, jumper wires and a 12 volt battery. I use air pressure with the sender to test. Wire it up the same way it would be in a car. Thread on the sender and feed in compressed air with an accurate gauge on the air pressure and compare readings. The photos below are from the year 2003. Here I am testing an original DELCO 1970 Buick GS oil pressure sender using an ohmmeter and my compressor. But I prefer a direct wire test using a 12 volt battery if the dash gauge is in question.

Thanks Pete. Have you seen a repop gauge get hurt by an overpressure situation?

[Peter Serio]

Running any one of those gauges past their numerical markings over 60 PSI on the dial is probably not good.

Impossible to say without first seeing the gauge in-person and testing it. I built a decade resistor box that has fixed ohms values in it for all of the various gauges that I work on.

I have tested those reproduction oil pressure gauges & found that they read, in most cases higher on the dial than true. It can be fixed, there is a comparison resister in series with one of the coils. That resistor is soldered in place so the gauge has to come all the way apart to get to it. Another thing to consider is the oil pressure sender. Where did it come from? Is it new or old. Is it a made in the USA part or an imported part? Every year that goes by they figure out a way to cost costs and make service parts (especially for a car that is 50+ years old) cheaper & cheaper.
They surely can make a Front strut tower for a 2002 Honda Accord but when it comes to cars that are no longer in daily use they seem to not put in the quality the same way that these kinds of parts used to be made.

[Rich-Tripower]

Originally Posted by Peter Serio

Running any one of those gauges past their numerical markings over 60 PSI on the dial is probably not good.

Impossible to say without first seeing the gauge in-person and testing it. I built a decade resistor box that has fixed ohms values in it for all of the various gauges that I work on.

I have tested those reproduction oil pressure gauges & found that they read, in most cases higher on the dial than true. It can be fixed, there is a comparison resister in series with one of the coils. That resistor is soldered in place so the gauge has to come all the way apart to get to it. Another thing to consider is the oil pressure sender. Where did it come from? Is it new or old. Is it a made in the USA part or an imported part? Every year that goes by they figure out a way to cost costs and make service parts (especially for a car that is 50+ years old) cheaper & cheaper.
They surely can make a Front strut tower for a 2002 Honda Accord but when it comes to cars that are no longer in daily use they seem to not put in the quality the same way that these kinds of parts used to be made.

Or they make parts in a "one size fits all" situation. They make parts that will FIT, but might not be specifically tuned to that particular year, etc. For example, it is nearly impossible to find a vacuum advance can for the L79 that is actually correctly calibrated to the L79 (it pulls much lower vacuum at idle than other small blocks) but every parts store in the country will get you one that fits, so what if it doesn't actually WORK correct.y.

[Peter Serio]

I see that all the time, after cars get way past the point of big numbers registered and tagged to drive as a daily car that people need to drive to get to work. The aftermarket will start to make parts for them of lesser quality. The one thing they love to do is take 10 or 15 years worth of part numbers and combine those all into one. Then they simply make one replacement # that they sell for all of those cars. Sometimes those part(s) fit, sometimes they don't. Often they will bolt on however the way they work may be close to original but in some examples it does not match the original GM part on specifications. Best to go with original however in many cases you can't find NOS GM parts that are still good; that fit a very desirable 50+ year old GM muscle-car.