yup.
What else are you doing to your engine? Unless you're running a cam and other mods the heads are not likely to be the bottleneck.
I use the small chamber heads on my pullers and cut off the ridge around the combustion chamber to raise the compression-we're
not allowed to run cams so this helps them out at the lower rpm levels we run (4000 or so under load).
I only do porting, head works and tweaking/ tuning the carb. Ah, sorry, and 'oil mods' of course!
I do not plan to install a racing cam, billet rods or forged pistons.
These components shall stay stock to keep (a) costs down since this engine will only race in 'farmer's fun races' and not competing in a national championship, (b) it is very hard (impossible) to come by such high-performance components here in Germany which means ordering them from the USA -> leading to very high costs, (c) max. RPMs will be kept under 4000 revs; I am looking for more grunt from below (to better get out of turns on muddy soil) rather than high-flying horses , yeah, that's it I guess.
The stock flywheel should be changed to a selfmade steel or (heavy, i.e. thick) aluminium one with bolted-on platic fins - this is the ultimate plan. I have some fear spinning the stock flywheel near and constantly about 4000 RPMs...
By the way, does anyone have dimensions as a drawing of the stock flywheel? This would save me a lot of work measuring everthing myself ;-)