ok boys and girls,I have built several 440 and 460 motors,with 1.3 rockers,.310 cam,flat top piston,and 0.080 shaved off the head the intake valve will hit the piston on the down stroke of the engine,this will give you a C.R of 12.5 to 1,now this all depends on what valve you are useing,the valves we use in our motors are custom made titaniam with very small margins this helps with valve to piston clearance,we also use a custom domed and valve relevied piston that I had desighed,we run big valves,small stems,and our last set of heads flowed 170cfm on the intake and 150 cfm on the exhaust,we can spin our engines to 9500 rpm all day we are making 60 HP at the crank our bigest problem to date has been chains,I can snap the best #35 chain at will at 80mph,we have just had bulley clutches,make us some #428 sprockets for the 1 inch turbo clutch this should fix the problem,feel free to ask me any thing about these engines