Regardless that the Blacktop head contains a far more open combustion chamber (see “Head combustion- chambers”) it even now has a greater static compression ratio (see “compression ratio”), this is only due to the piston layout. The Silvertop piston contains a very little dome with two deeply angled exhaust flycuts, https://andrennnkj.canariblogs.com/detailed-notes-on-blacktop-4age-for-sale-46505839