Leaderboard

Most of the more inexpensive lawnmowers are "flat head". Their valves are in the block and the motors are less efficient because of it , but they are cheaper to produce. I haven't pulled any of the newer utility overhead valve motors apart to see if they are push rod or overhead cam. They are more efficient and develop more power , but at greater expense to manufacture. ATVs have mostly overhead cams because they are more efficient and can easily be made to rev much higher because the push rods and rocker arms are eliminated. There is less mass to keep in reciprocal motion with overhead cam actuated valves. Less mass - easier to move - and less chance of valve float at higher RPMs. The motors can easily produce more power per cc in an overhead cam motor than in a push rod engine.