Despite the fact that the Blacktop head features a extra open combustion chamber (see “Head combustion- chambers”) it continue to has a greater static compression ratio (see “compression ratio”), this is solely due to piston structure. The Silvertop piston contains a extremely smaller dome with two deeply angled exhaust flycuts, https://toyota4age81470.weblogco.com/31426250/4age-20v-blacktop-fundamentals-explained