Despite the fact that the Blacktop head features a extra open combustion chamber (see “Head combustion- chambers”) it continue to has a better static compression ratio (see “compression ratio”), this is purely due to piston style. The Silvertop piston features a very small dome with two deeply angled exhaust flycuts, https://israelohtnl.blogocial.com/how-much-you-need-to-expect-you-ll-pay-for-a-good-4age-20v-for-sale-67285840