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Old 08-20-2012, 10:24 AM
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Thanks for the reply! Good info!

Quote:
Originally Posted by cobalt327 View Post
Are yiou using self aligning rockers?
yes

Quote:
Originally Posted by cobalt327 View Post
Just so we're on the same page, "zero lash" is when the clearance between the cam lobe, lifter plunger, push rod, rocker arm, and valve tip is removed. The lifter plunger must not be compressed until it bottoms out- only remove the clearance w/o any compression of the plunger. The ONLY compression of the plunger allowed is the 1/2 turn you're adding after reaching the zero lash point. If the plunger is bottomed out THEN 1/2 turn more preload is added, the valve will now be held off the seat and the engine will not be able to make any compression, so will not start.
Thanks for clarifying. I guess I got confused because there are so many people that say twist the pushrod until there is resistence while tightening the nut, or wiggle jiggle pushrods until they stop moving. I guess this is more of an issue with OEM stamped steel rockers and the ball and socket trunnion and/or OEM nut. Perhaps there just isn't enough tactile feedback that the system us now at 0 lash.

Quote:
Originally Posted by cobalt327 View Post
You may have read that the plunger should be midway between zero lash and fully compressed, or in the older factory manuals as much as 1-1/2 to 2 turns may have been recommended.

The basic idea is for the lifter plunger to be compressed enough that the lifter will compensate for changes in the valve train due to small amounts of wear and to changes in clearances due to temperature. This gives a fairly wide range of adjustment. But it has been found that under most circumstances, using 1/4 to 1/2 turn of preload works well.

Because motor oil isn't compressible, as soon as there's pressure applied to the lifter's pushrod seat, the lifter is basically solid. There is clearance that will allow the lifter to "bleed down" over time, but in the brief period of time that the lifter is cycling, the amount of movement can be dismissed as far as setting the geometry goes.
I think this really clears it up. The plunger should only be compressed by the amount of preload (1/2 to full turn) at any given time during operation.

Quote:
Originally Posted by cobalt327 View Post
I don't see how you're getting a good swipe mark using the method you've described. But in any event you need to use a solid lifter. You can use one like you are using and stack small washers into the center until it's a solid or you can use a solid lifter- as long as the seat (where the push rod sits) is the same height as the hydraulic lifters you're using.
What don't you like about this swipe mark I posted? I looked and it doesn't appear that I can't dissassemble these lifters easily. I think most lifters have a normal snap ring, but these Comp Cams lifters have some sort of bent wire retainer. I am not sure I can get them apart with my tools/skills without damaging them. I will do some research and see what I can come up with.

Quote:
Originally Posted by cobalt327 View Post
I would suggest you get or make a solid lifter, install the head gasket w/the bolts tightened to 40 ft/lb, and recheck the measurements to see if they vary from what you saw earlier.
I have a solid lifter, but the pushrod cup is quite a bit lower than where the plunger sits on a hydraulic lifter.

Quote:
Originally Posted by cobalt327 View Post
I'd be curious to see what the results would be using a different rocker. If you have a different rocker arm you can use- even a stocker- give it a try to see what it gives you.
Do you mean use a stamped rocker? I do have the old self aligning rockers from the Vortec laying around.
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