Pressure test at, or slightly above the rating of the cap you intend to run. It would be difficult to convince me to use water heat on an intake, since when the heat is needed most the coolant is cold. Of course, it would be even more difficult to get me to run a dual carb system that the cylinder head can't use efficiently. "It looks cool" isn't a good enough reason to go to all the effort and expense!
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!