wow. a blanket endorsement without any care as to whether or not the exhaust and intake durations overlap. wow.
Absolutely a blanket endorsement of Philip Smith's books!
A lot more "heady" and harder to read than Gordon Jennings.
I suspect he might have been some of Jennings source material.
I have "hot-rodded" most engines I have ever owned, including my lawn mowers and rototillers.
A 12"-18" piece of straight pipe generally increased the torque of any of them.
The rototiller got an even longer pipe (24"-30"???) which helped its torque considerably.
No math theory went into this, I just kept adding iron pipe and couplers until it worked the best.
With the pipe aimed at the ground no muffler was needed. Reasonably quiet (as a muffled Briggs&Stratton).
The Briggs definitely has overlap, it is only the rare blower or turbo 4 stroke that doesn't.
Port momentum (any pipe length +6") helps any 4 stroke engine with overlap.
Longer lengths help to provide a suction as it opens, usually on a harmonic because we cannot make the pipe long enough for the low rpm of the Briggs.