Difference between b16a, b16b, b18c and b18cr head...?

[zamrioo2]

how do i know the difference...? is it true b18c has bigger combustion chamber than b16a...? mine is b16a which has circle shape from bottom view, but somehow, i've seen some heads look like kacang shape(not in circle)... what kind of that head...? which one is better in flow...

 

[BtLeJuiCe]

From what I know, the B16A block is shorter (263mm) than the B16B and B18C (both 270mm), so I suppose the head for B16A is shorter than B16B and B18C.