Something else to keep in mind when changing rocker ratios... It isn't only valve to piston clearance thats an issue... There is also pushrod to cylinder head & block interferance that can be a problem... To change the ratio the effective leverage (ratio) is changed.. Your not changing the distance of the valve stem to the center of the rocker fulcrum so therefore you must be changing the distance from the center of the rocker fulcrum to the pushrod.. To increase the valve lift you need to shorten the distance from the center of the rocker fulcrum to the pushrod... So that potentially brings the pushrod into contact with the block or head...