Harley engines run more spring pressure than your typical car engines, and aftermarket springs for HDs are about 50+ lbs heavier seat pressure than aftermarket springs for car engine hydraulic rollers (aftermarket car hyd rlr cams typically run 125# on the seat.) Since all cams have had computer designed lobes for about the last 30+ years, I haven't run into lifter pump up in anything since the 1980s.
IMHO you should be using forged pistons with any large cam installation anyway, and the Weiscos that we use have HUGE valve notches. My Screamin' Eagle 257 (252/260@.053 at .569 lift and is a nice upper mid range street cam) has over .200" valve/ piston clearance with the deck set at .003 height. If my lifters pumped up solid they might hit, but they never have been close even when I was trying to hurt something even at 6700 rpm with the rev limiter disabled. The power is over by 5900 rpm with this cam in my 110 anyway, so how much more would I have to rev it over the 6700 rpm that I tried to hurt it at? My philosophy is breaking something gives me an excuse to build it bigger and faster next time. I do my "acid testing" on the dyno before I drive it hard. Just some random thoughts from the TIMINATOR
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Topic: Woods directional lifters (Read 7663 times)