proptop.thanks for backing me here I have run the 12-4 and the 12.25-3.75 and I get 13500 and 13100 on them. I have a mini tuned pipe on the mvvs and the tower muffler won`t fit, so my next option here is a portjob to squeese out even more power although as Dar Zeelon pointed out my engine will wake up more after some more runtime. I wrote that I never had ruined an engine before..well thats not entirely true. I modded a Dynamite mach 26 car engine this way and added a 9mm carb as opposed to the 7mm stocker.that engine ran like a scalded cat and the rod snapped after a gallon of fuel.way more rpm than it could handle, so I call that modding successful