Think of all that air and fuel in the cylinder going BACK through that small transfer slot then igniting. Its like a pre-combustion chamber, everything lights off very quickly. I know the surface area on any of our flatheads is less than any V8 and for sure any 4 valve head. Penthouse chambers have a very dead chamber as far as mixing the A/F. That is why racers use a curved dish piston to try and get the mixture to swirl and tumble on the up stroke of the piston. They also have little or none as far as quench area.
Just my thoughts
