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Lashing valves - hydraulic roller cam
What is zero lash? Is it when there is no up-down pushrod movement, or when there is "some" drag when spinning the pushrod between your fingers, or when the pushrod doesn't spin at all?
help. phil |
When there is no up/down movement. You can't really go by drag at all.
The best way to do it is with the intake off...then you can see if you're depressing the plunger in the lifter or not. Of course zero lash is when the plunger hasn't moved and there is no slack in the pushrod/rocker arm. |
Thanks Brent. However, I don't think I'll be pulling the intake to set the lash! That wouldn't be fun at all. :LOL:
For a hydraulic cam, is it zero lash plus a half turn? Thanks again. |
If you want to get anal, it actually depends on what lifters you're using. Comp Cams advises 1/2 turn to 3/4 turn depending on what lifter of theirs that you're using. You can probably look on the manufacturer's website and they should tell you what they recommend in either number of turns or in a dimension of preload.
For instance, if they tell you that .020-.040" preload is good, then you can judge how much .020-.040" is by looking at the threads on your adjuster screw or measuring how far the plunger is depressed in the lifter. You should be safe with 1/2 turn though. :D |
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Yeah, I glanced up at this profile info and saw what he was working on after I wrote that....
Little different....LOL |
Another issue about the 1/2 turn----IF the rockers are stud mounted the preload changes according to the rocker arm ratio----if rockers are shaft mounted the preload changes directly according to thread pitch.
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Comp Cams has an excellent article on their web site on exactly how to do this job.
Finding zero lash is actually pretty easy. Turn the nut with your hand. You'll feel it when it hits resistance. That's zero lash. Don't use the "push rod spin for drag" any more. Once they're adjusted correctly, I can still spin the push rods by hand. How much to turn past the zero lash depends on the set up. There's the variables mentioned above. AND, some lifter makers recommend more or less lifter pre-load. Ford recommends 2/3 turn for their SB lifters. I have a specially modified set, and only 1/3 is recommended for them. So check with whoever made the lifters. You could always put a dial indicater on the tip and measure the pre-load exactly. |
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