Was the distributor rotor pointing toward the low cylinder's spark plug wire during the air pressure test? If so, and you were getting air from both intake and exhaust, something's WAY wrong- - - -bite the bullet and pull the cylinder head. Back both rocker arm adjustments off so there's a BIG gap between the rocker tip and the valve stem- - - -like 1/4" or more, and repeat the air test. If you get intake or exhaust leaks that way, pull the cylinder head and do a visual inspection.
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!