pee vee

Hi all,
Just a quick question

when setting cam timing with vernier pulleys and hydraulic lifters,
Do you guys make any allowance for 'lifter pump' at higher RPMs?
As what you set at, say 1.25mm lift at TDC, might become 1.3 or more
at say 6500+ rpm.. throwing the settings out a little bit.

do the lifters pump up enough at high RPM to make it worth even worrying about?


thanks!

tabetha

The cam timing is nothing to do with jacked up followers, just set to what it should be timing wise and if the lifters pump up they hold open the valves so limiting further revs and damage anyway.
tabetha

pee vee

hmmm. dont really follow. if you set the valve to be open as my example of 1.25mm at TDC, then you get lifter pump at higher RPM, surely its gonna have the valve open more than 1.25mm at TDC... so throwing the settings out?


or am I looking at this the wrong way? i spose weak valve springs would be more of a problem than this.. lol

tabetha

The lifters will not go over thier prescribed design length if they are the corect ones for the cam's rev range, but yes if they pump, you may get a tad more lift, not so much as to cause a problem though as by then the lack of fuel air compressing and burning correctly will cause a natural limit to the revs anyway.
tabetha