Even though the Blacktop head contains a additional open up combustion chamber (see “Head combustion- chambers”) it even now has a higher static compression ratio (see “compression ratio”), this is purely due to the piston style. The Silvertop piston features a quite tiny dome with two deeply angled exhaust flycuts, https://bookmarkdistrict.com/story18271255/little-known-facts-about-4age-20v-itb