While the Blacktop head contains a a lot more open up combustion chamber (see “Head combustion- chambers”) it still has a higher static compression ratio (see “compression ratio”), this is purely due to the piston style. The Silvertop piston contains a very tiny dome with two deeply angled exhaust flycuts, https://toyota4ageengineforsale00187.bloggazzo.com/30652408/details-fiction-and-toyota-4age-blacktop-engine-for-sale