Lifter preload cross reference
Instructor
Joined: Dec 2001
Posts: 113
Likes: 0
From: Grand Rapids MI
I realize this is an old thread, but it comes up in searches, so I wanted to address a common misconception that I have seen here on at least 3 occasions. When measuring preload, you can't simply use the amount of turns on the bolt past zero lash and then multiply that by the thread pitch. Because the valve side of the rocker remains at the same height, and the pushrod tip is moving on a wider radius than the trunion, you would need to use a ratio to calculate the resulting preload at the lifter. In the case of a 1.7 to 1 rocker arm, if the valve tip to the trunion has 1.7 units of measure, then the trunion to pushrod would have 1 unit. Since tightening down the rocker with the tip contacting the valve works in a different manner, you would need to take 2.7 units for the total length of the rocker and divide it by 1.7 units for the valve to trunion. 2.7/1.7=1.59 in this case. So with a 1.7 rocker in place, preloading 1-2/3 turns with a 1.25mm pitch bolt would not result in 2.08mm of preload. It would result in 3.31mm of preload, which is just over .130". Likewise, 2.08mm (.082") of preload would correspond with slightly over 1 turn of the rocker bolt past zero lash.
Pro
Joined: May 2009
Posts: 728
Likes: 71
lifter
I know this is an old thread but I recently purchased lifter part#12576400, these are a different part# than the lifter I recently removed (part# 17122490). The question I have will they be ok to use given the preload, and full travel (see below) are slightly different?
[/QUOTE]
[/QUOTE]
Last edited by msd127; Oct 25, 2016 at 10:54 PM.
