the cam profile that i use will fit onto a 31mm bucket .my pistons are forged with a higher bump to give the 13.5 to 1 comp and uses longer rods as well ,i have both heads here as i dont use the std valves on any of these motors .only use the head with new valves and bigger plus different valve springs for the 13 mm of lift ,.head is ported and flowed and valve sizes are upped to the max