I have no idea how you figure that. The 1 and only advantage the 273 has is a lighter piston. (The potential to rev up quicker.) There is absolutely no reason ether engine would haves problem matching rpm for rpm.
273-2 had a helluva piston pin. So much as to make it the same weight as a poly 318's bobweight. 273-4 had a thinner wall pin to offset the taller pistons weight.
