There must be an acceptable safe limit to changing the gap. Wonder how much?
Based on several years of dyno testing, half the clearance ramp height is about the maximum variation I'd recommend. Beyond that there's a danger of holding the valve open when hot if the clearance is reduced further, and a real risk of battering parts if it's increased too far. It's still a "race only" modification, or something a really stupid street engine builder would try. Doing race engine stuff on the street is a surefire indicator that somebody shouldn't be tinkering with anything more complex than a hand-cranked can opener!
Jerry
