y is it that je 12.5 compression pistons for a b20 with a b16 head come out to be 11.7 when u calculate it on c-speedracing

 

cuz the heads are different

 

no it said 12.5 for a b20 with a bd which i have

 

i would trust the piston maker over c-speed racing, they probably are using the formula to calculate compression for the motor, which takes into acount stuff like bore stroke cylinder volume and other stuff to calculate