Setting pre load
Posted: Wed Sep 30, 2009 10:56 am
The method specified on the RPI web site for setting cam follower pre load looks a little hit and miss and can't be done on a built up engine, my proposal is therefore following am I missing something?
1. Put spacers between the rocker posts and followers until there is clearance on all valves (when valves closed), in my case this was 2mm.
2. measure the valve clarance turning the engine as you would to set the clearances with solid lifters.
3. calculate the pre load using a rocker ratio of 1.6,
preload = (Gap/1.6) - (shim thickness*1.6)
Do this for all 8 per side, in my case preloads were :(in mm)
-3.20,-2.45,-3.11,-2.70,-3.11,-2.67,-2.61,-2.51
Aiming for a target of between .5 and 1.3 mm gives a shim of around 1.2 mm (1.6 x the shim = prelead change) just about brings them all in range.
Any thoughts?
Kevin
1. Put spacers between the rocker posts and followers until there is clearance on all valves (when valves closed), in my case this was 2mm.
2. measure the valve clarance turning the engine as you would to set the clearances with solid lifters.
3. calculate the pre load using a rocker ratio of 1.6,
preload = (Gap/1.6) - (shim thickness*1.6)
Do this for all 8 per side, in my case preloads were :(in mm)
-3.20,-2.45,-3.11,-2.70,-3.11,-2.67,-2.61,-2.51
Aiming for a target of between .5 and 1.3 mm gives a shim of around 1.2 mm (1.6 x the shim = prelead change) just about brings them all in range.
Any thoughts?
Kevin