ok thanks so you would say if the motor i have came with a 2 mill and 1 mill shim i can use the one mill and not worry about pitting unless it was to lean as long as i had glow plug clearenace corret. So early cumbustion does not pit the motor which is what i read on another. and if i wanted a later one i can go too a two mill shim which would be better for fuel cause im still tying to find a race motor for my d8t i have a 427 and a mach2 .28 which are good but if they dont hack my large track i think of the b5 or os .25 but the price is high for os but i would like that power since it what im used too from my maxx.