Quote:
Originally Posted by nhgunnut
For anyone who needs me to clarify my opinion. I believe that an OHC at the same displacement and degree of tune will always outperform a Pushrod engine. This is in part due to less reciprocating mass and as always fewer moving parts equals less to go wrong. I also recognize that an OHC is more expensive to manufacture and requires a different skill set to tune and maintain. ( A good illustration of the impact of economic on engine performance is that as far back as the late teens racing engines routinely used overhead valve conversions but it wasn’t until the late 30s early 40s that overhead valves were available on affordable cars)
In terms of motorcycles the best comparison I can come up with is the 2 Air cooled American cruisers on the market today HD using its Pushrod engine producing HD big bore producing 66 -71 RW HP (some one help me with the torque ) and My Wife’s 03 Victory big bore 92 RW HP with 94 ft lbs of torque. (my Victory doesn’t count cause I have tweaked the shit out of it) The numbers are at the rear wheel not the lovely “at the crank” fairy tales that every manufacturer seems to have. The major difference in the engine are 100 CI Victory OHC 103 CI HD pushrod, HD 45 degree V twin inline cylinders requiring “Knife and fork” connecting rods ,Victory 50 degree V Twin off set cylinders using standard connecting rods.
Just for the sake of clarity Star (Yamaha’s Cruiser line ) Upper models us a push rod air cooled monster.
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The big HD engines I saw in IA on the dyno were putting down mid 80's hp and around 100 ft/lbs torque at the rear wheel.
mostly stock, but many had an exhaust on 'em.