Yes I have done many compression checks and figured compression ratio on this method. You take 1 plug out and put a fitting into the plug hole. The fitting has a vacuum hose that runs to the compression gauge itself. This procedure is in every automotive manual that I have and have been told by many mechanics to do this. Haynes, ford thunderbird, mercury cougar, 1989 -1997 haynes repair manual, chapter 2 part C section 3, cylinder compression check is what I am refering to. Get any manual and look it up, or ask any full time mechanic, not a weekend backyard mechanic.