I know from racing OHH engines, that imcreasing the exhaust valve size did result in lower bottom end, especially on tighter tracks. I had a couple of heads that were ported, had good valves and springs, and even one with a welded up chamber for more compression, that I used on smaller tracks.
These engines are drastically under square with the big bore and short 1.938 stroke, which by itself hinders low end torque.
I agree with Delray that building a stock or even slightly warmed over engine, the small valves might even be a good thing, especially for a heavier bike/rider.
Here is one of the stock valve ported heads I used to run. That head still made great power even having the small valves. In fact, I patterned the chamber the OVRM head on my 356 build after it.
These engines are drastically under square with the big bore and short 1.938 stroke, which by itself hinders low end torque.
I agree with Delray that building a stock or even slightly warmed over engine, the small valves might even be a good thing, especially for a heavier bike/rider.
Here is one of the stock valve ported heads I used to run. That head still made great power even having the small valves. In fact, I patterned the chamber the OVRM head on my 356 build after it.
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