If you can block off any kind of crankcase vent system and figure out a way to adapt a vacuum gauge to a valve cover or an oil filler cap you'd probably be able to see at least some vacuum on the crankcase. One of the "smoke generators" used to find leaks in closed loop ventilating systems on newer emission controlled cars might be useful if a test procedure could be developed. If your buddy is dealing with a milled head and a poorly-fitting intake, installing new gaskets might only be a temporary fix until the vacuum distorts the new side gasket. If it was just a gasket installation mistake previously, he might have made a permanent fix this time.
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!