Not looking for a debate here, just wondering with the stock GX390 head what is the biggest intake and exhaust valves that can be put in the head without using larger seats. (keeping factory seats). Also if Stock piston was to be milled to be a flat top, is there a billet rod out there and what length to bring the piston further up the cylinder closer to deck using stock stroke crank?
Thanks,
Matt
Thanks,
Matt