Farmall Cub

Can anyone tell me if it makes any difference when running a compression test on the cylinders if all other spark plugs are removed, left in place, or no difference at all.
Thanks

It should be done with the plugs out and the throttle open. In a practical sense, I haven't seen it make a notable difference.

Jeff,

The starter turns the engine faster without the spark plugs. Chances are you'll get lower readings with plugs in place, reduced speed gives more time for compression to leak. Also, compression should be checked with engine at operating temperature.

Lurker Carl