make sure your not hitting the bottom side of the piston to crank counter weigths .oilpan screen or wind tray.oil pan hitting crank counter weigths check that the crank counter s are not rubbing on block casting .check bottoms of pistons bores that rods are not hitting . rods side at 008 is abit thin .built them with much more .i would say thats not it or floaters .less one of the pistons pin s is working its way in to the piston bore . you have the rigth firing order ? for your cam