I'm getting ready for a valve spring swap.

I threaded an adapter into the #1 spark plug hole, attached an air hose, and rotated the engine until both valves were closed (not sure if it's TDC or BDC). I turn on my air compressor and it builds a max of about 35 psi. When I shut off the compressor I can hear the air leak out.

I have even backed off the rocker arms to make sure the valves are closed. The car has been sitting for a couple of months. Could it be that the rings are dry and that they are not sealing? Could it be that my valves or valve seats are damaged and not sealing.

Any help would be appreciated.

 

You need to listen and check a couple places to figure out where the air is going. Intake (carb), Exhaust (tailpipe) or crankcase (breather). It's also possible the air is leaking through a BADLY blown head gasket into the next cylinder over or into the cooling system.

 

I don't think it's a blown head gasket because I just tried a cylinder on the pass. side of the engine and it's the same story. The engine has always run fairly well so I'm not sure what to think.

Again, I wonder if the fact that it had been sitting so long could have caused the rings to lose their coating of oil. I cranked the motor with my remote starter for several second to try to oil up the engine but it didn't make any difference. Hmmm.

 

If thats the case get a oil squirt can and put 3 squirts in the spark plug hole

and crank it over(after reinstalling plugs) with flood clear mode, Either way.. it cant hurt

 

That seems like a good idea. Too bad I can't find my oil can.

I suppose I could put it back together and run it for a minute or two to oil up the rings. Maybee that would make a difference.

 

Try listening first though, you can eliminate the others that way.

 

I hear the air rushing our of the cylinder. I listened at the carb and that didn't seem to be it. I can't tell if it's going out through the header or past the rings.

The air hold adapter seems to be air tight. I don't want to torque it too hard because the last thing I want is to strip the spark plug threads.

Tomorow I'm going to put it back together and run it for a while to make sure the rings are lubed and then I'll try again.

I read that when doing a compression test you are supposed to remove all 8 plugs. In my case I'm only removing the one plug I'm working with. Would that have any effect?

 

It sounds like you're not performing a cranking compression test, but simply trying to pressurize a cylinder. For a cranking compression test, it is best to remove all the spark plugs and block the throttle open. That doesn't seem to apply in this instance. Your compressor must have adequate displacement to fill the cylinder. If you're using one of those 12V emergency compressors designed to inflate tires, it may not have that capacity.