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Thread: cam running clearance
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10-07-2004 #1
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cam running clearance
what is this a measurement of, and where is it taken. is it the clearance between the rocker and the top of the valve spring?
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10-07-2004 #2dennis68 GuestI've built dozens of engines and have never heard of this. Maybe you could carify exactly what clearence you are interested in checking.
10-07-2004 #3
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well, i have a hyd. roller cam from howards and on the cam card it says running clearance 000. this is near the lift numbers on the card.
10-07-2004 #4
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That means it has no lash setting. A solid might have .018" lash for example; a hydraulic would show "0" clearance as they are actually pre-loaded, no lash involved.
Jody
10-07-2004 #5
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ok, that makes sense. this is the whole tighten the rocker nut till pushrod cant be rotated any more then got 1/2 turn more then tighten the poly lock correct.
10-07-2004 #6
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That is correct, but if your lifters are not primed, you will get a false reading if you wait untill you cant turn the pushrod. Just run it down till the pushrod has no play in it, then turn it half a turn. Not sure what kind of engine you are building but if its just a old school engine, watch to make sure the lifter does not compress before the half turn. If its a ls1 you cant see them. At times they can be a major pain.
72 El Camino (LS-1)
10-07-2004 #7dennis68 GuestGottcha. All hydraulics are going to be .000. Solids would be somewhere between .015 and .030".
Yes, spin the pushrod until all preload is removed and then add 1/4-1 full turn (it's a preference thing, sometimes you can pick up a tenth or 2 by adding/removing some lash this way).
10-08-2004 #8
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Adjustment
Some of these hydraulics like running at -0-, in other words, no preload. A easy way to adjust them on a new build is doing it with the intake off, tighten the rocker and simply watch the lifter plunger unseat. I like to run them as loose as possible without having lash, just moving the plunger off the retainer. Simply rotate the engine until each lifter is down and go through them one at a time.
10-08-2004 #9
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I set hydraulic lifters the same way Prodigy does. Almost impossible to do with the intake on the engine, but eliminates any chance of lifter pump up.
KenIf there is a hard way to do something, I'll find it!
My other car is a Vega.
10-08-2004 #10
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The less pre-load does make most any hydraulic cam perform better; the rpms increase, vacuum increases, etc. But be careful as many hydraulic lifters can't handle any slack in the lash and can break the retaining clips and have the lifter guts all over the place. I usually run 1/4 to 3/8 of a turn pre-load to be safe.
Jody
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