Can it happen? Sure. Did it happen? I dunno, if Your porting greatly enhanced chamber/cyl. swirl, it would be more resistant to detonation. But a whole bunch of other things could have been affected, signal at the carb's mains at a given RPM etc., running vac adv.? Is that the only change that was made? Quantify what You were/are running base/mech/vac for Us if You would.......
