you want to make hp on regular gas you need some tight quench
open chamber heads take rpm (more cam, gears, converter) and high octane to make horsepower
I helped design the quench head pistons/ step dish pistons working with John Erb at KB- others smarter than I - some with propane experience- a real genius, and Speed-O Motive (they have left the strip I'm sad to say) also helped to solve the problem with the MOPAR open chamber heads. Speed-O-Motive used to weld up the chambers- it's that bad
