[pdxmotorhead]

The M42 has better valve control than the M44. Plus a forged crank and a tick less rotating mass, I would strongly suspect the M42 will out-rev the M44 by 500 rpm.. given equal builds. Longer stroke usually means less ultimate top end rpm. If anything was going to let loose on a M44/M47 build I would guess Pistons. That build has a lot of stroke, so very high inertia on the top of the piston.