Your leakdown test procedure with the rocker arms removed is seriously flawed, unless you're also locking the crankshaft with each cylinder at the top of its stroke. That's where the maximum wear (and leakage) is present. The air pressure will push the piston to the bottom of its travel otherwise, where wear and leakage will beat a minimum.
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!