POA Valve Doesn't "pop"

[rrowe52]

I have a couple of POA valves for my '67 Corvette. One was rebuilt several years ago and on the car until recently. The other is a recently-purchased NOS part. I've had them both on the bench recently to test. The rebuilt valve was showing about 26lbs, but I was able to adjust it to 30lbs (I'm still running R12). The NOS valve was spot on at 30lbs.

Most accounts I have read for bench testing POA valves describe a "pop" that should be audible as the input pressure is slowly increased. Neither of these valves "pop", although there is a slight wobble in the gauge needle as the low side pressure reaches 30lbs. I'm running 60lbs on the inlet.

Both valves register pressure on the low side port as soon as any pressure is applied at the input. Opening the gauge valve on the input increases the low side pressure proportionately until it reaches 30lbs, after which it holds steady.

Seems like both are operating properly, but I'm concerned about the absence of the "pop". Any thoughts on this? Are these OK to use?

[JohnHere]

Most accounts I have read for bench testing POA valves describe a "pop" that should be audible as the input pressure is slowly increased. Neither of these valves "pop", although there is a slight wobble in the gauge needle as the low side pressure reaches 30lbs. I'm running 60lbs on the inlet.

You might or might not hear a distinct "pop" as the POA valve approaches its set-point at your 60-PSI input pressure. At slightly higher test pressures of 65 or 70 PSI (I wouldn't exceed the latter), you might hear a "pop." But in any event, you should notice an increase in the sound of the air flowing through the valve. The pressure and airflow should then level off right at the POA set-point.

Both valves register pressure on the low side port as soon as any pressure is applied at the input. Opening the gauge valve on the input increases the low side pressure proportionately until it reaches 30lbs, after which it holds steady.

Right. That behavior is perfectly normal for a healthy POA valve. Based on your test procedure, test pressure, and results, I would say that both of your POA valves are good.

[rrowe52]

Thanks!