Hi I am assembling a 2nd pair of heads for my old V8. this pair of heads will have adjustable rollerrockers on them.
The lifters in the block are hydrolic lifters
my question is - What do I set the valve gap to with these ajustable rockers? Im guessing ZERO to mimic the old steel rocker that you normally find in these heads.
With hydraulic lifters and adjustable rockers you want to preload the lifter a specific amount, .020" to .030" is common. Most adjusters have 24 threads so one turn equals .0417"; a half turn will preload the lifter about .020" and three quarters of a turn will preload about .030".
With each lifter on the heel of the cam lobe, turn the adjuster until all free play is removed (spin the pushrod to feel the drag at zero lash) and then turn the adjuster an additional 1/2 to 2/3 turn and tighten the jam nut.
what year 318???
John Kunkel wrote:
Hydraulic
No, you have to center the plunger of the lifter in its bore when its body is on the heel of the cam. Simply setting the arms to "zero lash" won't do anything constructive at all...you must adjust them so the plunger is in the center of its travel in the body. Most people do this while the engine is idling hot by backing off the adjusting nut or stud until continuous "click" is heard and then tightening them down around 2/3 of a turn.
Having adjustable rockers on a hydraulic lifter equipped engine isn't very useful; there are tons of better mods to do to that LA to get better longevity and/or efficiency, and this ain't one of 'em.
Oh, yes!! - Im not saying its a really usefull Mod - The roller rockers were all all I had in my parts bin, so Im using them - If I had new normal rockers, I might hav used those instead.
Nonsense, adjustable rockers allow one to adjust the lifter preload to a desired dimension rather than the happenstance preload that results from machine work. (head/block milling, valve sinking, etc.) Adjusting to the middle of the plunger's travel isn't the goal, adjustment is normally made to a minimum preload dimensiion like .020"-.030".
Only if you want to promptly burn all your exhaust valves, and/or kiss the pistons with ALL the valves. "The center of its travel" is WAY too much pre-load!!!! About .020 is correct.
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