Setting valve lash
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
From my paper (e-mail me for a copy):
- There is an issue of “feeling” for zero lash by either "twisting" the pushrod, as I suggest in this paper, or moving the pushrod “up and down.” I advocate rotating the pushrod between your fingers to "feel" when the zero-lash point is attained: You will be able to feel the pushrod "grab" right at the zero lash point as you're tightening the rocker nut. This is exactly "zero," and is the way the lash is set at the factory and by every racer I've ever known. I have seen some people, who must have very numb fingers, not be able discern when the lash goes tight: After the pushrod has grabbed, they will force-turn the pushrod between their fingers, continue to run the nut down, bleeding the lifter down, continue to force the pushrod to turn, and then bottom the lifter plunger out in the bottom of the lifter body. This will then positively lock up the pushrod, which they interpret as zero lash, and they then run the nut down an additional 1/2 turn, which will prevent the valve from ever closing. In my humble opinion, these people should not be working on an engine. But if they're going to, then the "up-and-down" pushrod movement is probably safer for someone like this. It is not as accurate for determining the exact zero point, but it's better than running the plunger down into the bottom of the lifter body.
Drifting
Joined: Jun 2025
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