Compression Check

[Jerry McConnell]

I did a compression check and vacuum check on my 31 Tudoor this weekend. I removed one sparkplug at a time and did the check. I was getting mid 35 psi per cylinder. The readings were higher at number 1 cylinder and seamed to get a little lower as I went through the rest of the cylinders. I saw a video on YouTube that said to remove all plugs when doing this check; should I do it over? My vacuum reading was 18 pounds with very little needle flux. I do hear a slight knocking noise from the number 4 cylinder that goes away after I remove the plug wire. The motor does not smoke bad and has a lot of pep. What do you think, is the engine worn out?

 

[Jim/GA]

You should repeat the compression test with all plugs out. Better to do it on a warm/hot engine, if you can.

Also leave the fuel valve turned off and open the throttle all the way using the lever on the right side of the steering column.

 

[Mike V. Florida]

Was there a problem that caused you to do the checks?

The vacuum check shows all is good.

 

[tbirdtbird]

he has a slight knock at #4. prolly time to do a babbit check and hope it is not a shrunk piston

 

[billwill]

Hold throthle open all way when taking this test good luck

 

[Jerry McConnell]

The car had been setting for years, I am working my way through the car.

 

[Will N]

Good plan to go through the car before running it. I'd make sure to drop the pan and take off the valve cover to clean the gunk out before firing it up for any period of time. But as mentioned by the fellas above, a proper compression check is done on a warm engine with all the plugs out and with the trottle held wide open. But I wouldn't get hung up on the compression just yet. I'd get myself comfortable that the car is running dependably, then take it out and drive it! There are hundreds of As out there with below spec compression and slight knocks that run servicably for years. And that slight knock may be a sticking valve which may be cured by running the engine.