The first most important thing for making good power in a reciprocating engine is a straight round hole and good ring seal
It all starts there - If ya don’t have that to begin with yer screwed
You can have the best rod length to stroke ratio, cam specs, cam timing, valve size, port cfm, valve job, ignition timing, a/f ratio, the best exhaust system in the world, and anything else you can think of (light parts, coated parts etc)...
It’s gonna be down on power if it’s not sealed up