>This reduction in friction is good for around 10 hp? I've read it's more 10-
20 hp...
Are you thinking of roller lifters? A cam designed to take advantage of
the reduced friction of a roller lifter can have somewhat more
aggressive valve-opening acceleration, and hence, a longer effective
duration, resulting in measurable horsepower increases, but the bulk of
the energy used at the rocker end is from compressing the valve springs
and overcoming inertia. Conceivably, however, roller rockers might
allow a slightly higher maximum valve operation speed, or greater lift
without excessive valve-stem side loads, resulting in overall power
increases.
Stuart Steele
1969 TR6
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