All you really need is an air hose and an old spark plug. File, grind, or hacksaw the crimp on the plug shell to release the porcelain and use a 1/4" pipe tap to thread the plug shell for an air line quick-connector. I've got a couple of those adapters stashed away somewhere, one for 14MM plug threads and another for the old Ford 18MM plugs. One of these days, I'll have to make one for the 10MM threads on some of the old 216's.

If you have a compression tester with screw-in adapters for the plug holes, just take the Schrader valve out of the tester hose and adapt the air pressure to it. A lot of compression testers use the same quick-connect fittings that air hose couplers have.
Jerry


"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!