Pushrod geometry question...
May 26th, 2016, 07:01 PM
#1
Pushrod geometry question...
Hello All! I am setting the rocker arm geometry on my olds 350 and I have a question: there are some I've noticed (videos mostly on youtube) that say when adjusting for pushrod length to color the valve stem tip and set the pushrod to the assumed length (for testing), install the rocker, finger tighten the poly lock down until 1 of 2 points:
1. Until the pushrod just begins to drag, or
2. Until the pushrod is almost tight enough not to be able to turn it
Then, give the poly lock a half a turn and then lock it down, turn the engine and check the mark to see if it is centered on the valve stem; repeat until it is.
My question: which of the two points above to I turn the poly lock to before giving it a 1/2 turn and then lock it down? It seems that is quite an important point because there could be .050 or more of a difference depending on the point at which one stops the poly lock.
Thanks!
1. Until the pushrod just begins to drag, or
2. Until the pushrod is almost tight enough not to be able to turn it
Then, give the poly lock a half a turn and then lock it down, turn the engine and check the mark to see if it is centered on the valve stem; repeat until it is.
My question: which of the two points above to I turn the poly lock to before giving it a 1/2 turn and then lock it down? It seems that is quite an important point because there could be .050 or more of a difference depending on the point at which one stops the poly lock.
Thanks!
May 27th, 2016, 06:01 AM
#2
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If you are installing aftermarket roller tip rockers like those made by Comp Cams follow the directions. I installed these on my 455 and as I recall the directions indicated to tighten the rockers until the pushrod begins to drag and then to tighten the poly lock. I've been running my 455 for many years with no excessive valve train noise.
If you have a stock valve train then all you do is install the lifters and pushrods and tighten the rocker arm bridges. Lash is hydraulic in a stock Olds motor.
If you have a stock valve train then all you do is install the lifters and pushrods and tighten the rocker arm bridges. Lash is hydraulic in a stock Olds motor.
May 27th, 2016, 10:47 AM
#3
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Join Date: Sep 2011
Location: Plano, TX
Posts: 1,846
Just begin to drag. I usually tighten and loosen around that area a little to get a good feel for when it really hits. You can also jiggle the pushrod up and down, but turning is easier to get a good feel. Just use a bit of engine oil for lube while checking, as globs of assembly lube can mess you up.
With the poly lock, give it just under half a turn, snug down the set screw, then give the poly lock a good push to lock it down - it'll turn another bit. Don't try to lock it solely by tightening the set screw.
You may need to turn the engine several times to get a good wear mark on the valve stem tip. Dykem is easier to use than a sharpie, but sharpies work.
Going until you can't turn the pushrod anymore **with a hydraulic lifter** means either the lifter is completely pumped up so you're still at zero lash, or you completely collapse the lifter. A pumped up lifter isn't a terrible thing - it'll bleed down when the engine gets running, so don't be surprised if the valve opens while setting the poly locks. Collapsing the lifter is a bad thing and will lead to broken parts.
Solid lifters, on the other hand, will load up the pushrod rather quickly. But the adjustment for those is quite different.
With the poly lock, give it just under half a turn, snug down the set screw, then give the poly lock a good push to lock it down - it'll turn another bit. Don't try to lock it solely by tightening the set screw.
You may need to turn the engine several times to get a good wear mark on the valve stem tip. Dykem is easier to use than a sharpie, but sharpies work.
Going until you can't turn the pushrod anymore **with a hydraulic lifter** means either the lifter is completely pumped up so you're still at zero lash, or you completely collapse the lifter. A pumped up lifter isn't a terrible thing - it'll bleed down when the engine gets running, so don't be surprised if the valve opens while setting the poly locks. Collapsing the lifter is a bad thing and will lead to broken parts.
Solid lifters, on the other hand, will load up the pushrod rather quickly. But the adjustment for those is quite different.
June 2nd, 2016, 07:46 PM
#5
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