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Discussion Starter #1
There have been lots of discusions on preload and zero lash setups but.....not a thread on the entire subject. Meaning its been hit or mis, it may take reading 10+ different threads to come up with an answer.

So here is my question...what is the total plunger travel of an OEM LS lifter ?? (from colapsed to full "pump" up)

And here are some internet rumors I'd like to sqwash or validate.

1) and this comes from a pretty reputable guy on the "vette" forum....

"When you tighten the rocker bolt to zero lash and then torque to 22 lb-ft, I found that it takes 1/3 turn after the rocker bottoms in the stand to reach final torque. The rockers were pretty consistent with this 1/3 turn. Once the rocker bottoms in the rocker stand, there is no more preload applied to the lifter. So if you use 1 turn for zero lash to full torque, only 2/3 turn are actually applying preload (bringing the rocker down to seat in the stand). For that case I get the following:

2/3 X 1.25/25.4 X 2.7/1.7 = 0.52

When the number of turns increases to 1-1/4, you still need to subtract the 1/3 bolt turn after the rocker seats in the stand.

(1.25-0.3333) X 1.25/25.4 X 2.7/1.7 = 0.071

Note that all of these are approximate but given the pushrods are available only in increments of 0.025" any of the methods should work. What Shane recommends is using turns to figure preload and if a pushrod is the wrong length try a different length to obtain the correct range of turns on the bolt. The math allows you to estimate the new length if you don't have different lengths available and provides another tool to work with and double check your work. One other tool that a lot of guys overlook is they usually have the stock pushrods available that will provide an estimate of length when counting turns using Shane's method, but the stock length is 7.385" and not 7.400" (I and others have measured similar length of the stock pushrods) as is the internet myth."



2) Same guy on adjustable pushrod use and finding a proper preload and wipe pattern....

"Each turn of the pushrod is 0.050". When fully closed, it is 6.800". This is pushrod "gauge length" so you can't measure it directly as the pushrod length is actually based on the length between the ball ends where the ball end measures 0.140" in diameter. Assuming you are using stock rockers or a non-adjustable rocker with a correctly established wipe pattern.

1. Open the adjustable pushrod to the same length as your stock pushrods
2. Close it down two turns
3. Put your rocker rail on the head
4. Make sure you cylinder (typically #1) is at top dead center on the firing stroke so both valves would be closed
5. Put the pushrod in place on the intake valve and make sure it is in the lifter cup
6. Install the rocker and snug down the bolt (don't need to torque, just make sure it is snug)
7. Lift rocker tip up and down, if it "ticks" the pushrod is too short. If you can't easily move the rocker the pushrod is too long.
8. You can try and adjust the pushrod in place buy my fingers are too fat so I end up pulling the rocker and adjusting the pushrod length. Go either shorter or longer 1/2 turn and try again.
9. You are trying to get to the point where the lifter doesn't "tick tick" with the pushrod in place nor is the rocker snug. When you get the pushrod length such that you just barely get rid of the "tick tick", you have found "zero lash".
10. When you have found zero lash, carefully remove the rocker and pushrod without rotating the pushrod.
11. Tighten the pushrod until it is fully closed counting the turns as you go.

To figure out your pushrod length you do the following. Lets assume it took 10-1/2 turns to close the pushrod down to its shortest length after you reached zero lash. Each turn is 0.050".

Your length is then: 6.800" (fully closed length) + 10.5 X 0.050" (number of turns times the length change per turn) = pushrod length minus preload. So for this case:

6.800 +10.5 X 0.050 = 7.325"

This is the length you measured to zero lash without any lifter preload. Now lets say you want to have 0.075" lifter preload, you add that to the measured number and you end up with 7.400" pushrods.

Now repeat for the exhaust valve to verify the length. If you have something like Yella Terra's, it is the same procedure but you must snug down the rocker pair rather than the single rocker."



Would these procedures be sound advise for setting my preload on my current LS project ??


Thanks.....
 

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Reading that made me want to stick a pencil in my eye. Definitely a Vette owner--no offense. But wholly fucking shit can we make mountains out of mole hills or what?

One full turn is .047" by the way.

It's late but will elaborate much later if I need to.
 

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Discussion Starter #3 (Edited)
Thanks Billyman....so what is the total plunger travel of a LS1/6 lifter ?? If I knew the travel...couldn't I just set the lash @ X with the lifter colapsed with feeler guage at the tip. Then when the lifter "pumps" up that would be the preload......... Example....if the plunger has a travel of .100" and .050" preload is acceptable, couldn't I just set the lash at the tip of the rocker at .050" (using the adjustable pushrod) and when the lifter pumps up it would have .050" of preload ????


Will the stock lifters take a 157lb close and 471lb open spring rate ??

I'm working on my valve train geometry with stock rockers with trunnion upgrade.

AT WHAT POINT SHOULD SOMEONE BE LOOKING AT 3/8THS PUSHRODS ??


Thanks.....sorry for such a newbie question !
 

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Discussion Starter #4
Looks like I just found what I was looking for.....goes like this

make sure your on the base circle
using a know length pushrod tighten to zero lash (rock becomes stable)
Take your torque wrench that is set to 22lb-ft and torque the 8mm bolt
Count the number of turns it takes to acheive 22lb-ft....1 full turn is worth .047"
Adjust the pushrod length accordingly for the desired preload

I read that I should be looking for .050-.065 range with my ls6 lifters.

Thanks....if this.is.wrong please chime in.
 

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Discussion Starter #5
Reading that made me want to stick a pencil in my eye. Definitely a Vette owner--no offense. But wholly fucking shit can we make mountains out of mole hills or what?

One full turn is .047" by the way.

It's late but will elaborate much later if I need to.
Hahaha.....after finding the answer, I'm totally fucking embarassed of my original post...hahaha.....You weren't kidding...mountain out of a mole hill !!

But I would still like an answer to the pushrod and spring pressure question.

Thanks....
 

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Whatever happened to taking a dial indicator and preloading the lifter with a physical measurement? That's how I set mine up with precisely .050" preload on LS7 lifters and never had an issue with valvetrain noise or instability.
 

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Also the lifter is "pumped" up just sitting there with no pressure against the plunger. There is a spring inside the lifter that pushes up on the plunger. So the easiest method is to get a pushrod checker, collapse it all the way, put cam on base circle, tighten rockers all the way down to 22ft lbs then slowly lengthen the expandable pushrod until you have zero lash but not puting any pressure on the lifter. Pull that back apart and measure the pushrod. The length you get is the length you would need for 0 preload. Add .050" to that and you have your preload.

If you have a spare lifter laying around pull the snap ring off the top lifter cup and take it apart and look at it, they are really simple in how they operate.
 

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Reading that made me want to stick a pencil in my eye. Definitely a Vette owner--no offense. But wholly fucking shit can we make mountains out of mole hills or what?

One full turn is .047" by the way.

It's late but will elaborate much later if I need to.
Yeah - no shit!

Makes me want to burn the wife's Vette...
 

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Yeah - no shit!

Makes me want to burn the wife's Vette...
If your name is on the title, you own a Vette too. :rolleyes:

To the OP, my Morel "street" link bar lifters are set at .020". When the engine first fired up it was real quiet. Now that I have a couple thousand miles on it, I get the noisy valvetrain sound until the oil circulates fully. While running is has a very slight sewing machine sound to it. I can barely hear it. I've shifted as high as 7400 on this motor when I wasn't paying attention to the tach. It was still pulling hard and when I noticed I went "oh shit" and shifted. My limiter is set at 7600. No indications of valve float up that high with the HUC lobes and Comp 921 double springs.
 

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Discussion Starter #10
Also the lifter is "pumped" up just sitting there with no pressure against the plunger. There is a spring inside the lifter that pushes up on the plunger. So the easiest method is to get a pushrod checker, collapse it all the way, put cam on base circle, tighten rockers all the way down to 22ft lbs then slowly lengthen the expandable pushrod until you have zero lash but not puting any pressure on the lifter. Pull that back apart and measure the pushrod. The length you get is the length you would need for 0 preload. Add .050" to that and you have your preload.

If you have a spare lifter laying around pull the snap ring off the top lifter cup and take it apart and look at it, they are really simple in how they operate.
Thanks shortuning.....there seems to be several ways from A to B.

What is the math used to figure pushrod length to rocker tip correlation ?? meaning if I "add" .025" of pushrod length what is the effect on valve tip wipe ?? Assuming preload stays the same ??

Thanks.......
 

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Discussion Starter #11
Disreguard....I found my answer....I keep on thinking like a gen 1 small block where the pushrod plays a role in rocker tip location. This zero lash setup is kind of new to me. This LS stuff.....the pushrod is just a function of proper preload on the lifter. The rocker is a fixed fulcrom in correlation to the vavle tip.

Thanks.....
 

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If your name is on the title, you own a Vette too. :rolleyes:

To the OP, my Morel "street" link bar lifters are set at .020". When the engine first fired up it was real quiet. Now that I have a couple thousand miles on it, I get the noisy valvetrain sound until the oil circulates fully. While running is has a very slight sewing machine sound to it. I can barely hear it. I've shifted as high as 7400 on this motor when I wasn't paying attention to the tach. It was still pulling hard and when I noticed I went "oh shit" and shifted. My limiter is set at 7600. No indications of valve float up that high with the HUC lobes and Comp 921 double springs.
My Morels are the opposite. At .060 preload at startup it's noisier then hell! Then after it warms up and the oil circulates it quiets down to the "sewing machine" level...
 

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The rocker is a fixed fulcrom in correlation to the vavle tip.

Thanks.....
That's right, and don't let anyone convince you to "shim up" the rockers unless it's a racecar only that doesn't get driven.

471 lbs open sounds too stiff for stock rockers to me, why so stiff? 400 lbs is a better number.
 

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My Morels are the opposite. At .060 preload at startup it's noisier then hell! Then after it warms up and the oil circulates it quiets down to the "sewing machine" level...
That's how mine is now. The first few hundred miles on the new motor it was quiet at startup though. Kinda freaked me out when it decided to break in more and got noisy at start up. I'm guessing all the heat cycles just made everything loosen up.
 

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Discussion Starter #15
I still have yet to hear what the total plunger travel is inside a OEM LS lifter. I would like to know so I can associate the preload to overall travel.

I've heard .050"-.080" for perload.

Is there any drawback to stepping up to 3/8ths pushrods (6700-6900 shift point). I'm have to buy new ones anyway...the old ones went with the old cam.

And to B. Tooley the springs that are on the heads are the PRC .675's (157lbs @ 1.800" & 471lbs @ 1.125"), these are left over from the more aggesive lobes that were on the old cam but they still check great so I thought I'd stick with them. If the lifters can take them (which they have for about 1000 miles and 20 times down the track) is there any drawback to a heavier spring rate (I thought they would help keep things stable at higher RPMs).

And one more thing....when I pulled this motors top end off I noticed a odd wear pattern on just a few valve tips. About 3 or 4 valve tips had a wipe pattern that extended to the edge (outboard/exhaust) of the valve tip (it kind of rolled the edge a little). All the pushrods were the same length and all torqued to 22lb-ft. So what the ??? And how do I avoid this with the next setup ?? FYI, stock rockers with trunnion upgrade. FWIW my take is the last cam was more aggressive in every aspect (LSK/XER w.650ish lift), which I think is maybe to much for the stock rockers. New cam is LSL/HUC w/.630ish...will the stock rocker be happy ??

Thanks.....
 

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Lifter travel of "LS7" lifters (which became the standard replacement lifter for LS1/LS6/LS2/etc, etc, etc in 2005) are specified by GM to have .220 plunger travel. Independent tests (mine) have shown variations of up .030".
 

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And to B. Tooley the springs that are on the heads are the PRC .675's (157lbs @ 1.800" & 471lbs @ 1.125"), these are left over from the more aggesive lobes that were on the old cam but they still check great so I thought I'd stick with them.
Too much spring pressure over the nose will eat up the valve tips and eventually the rocker tips. The damage usually starts by pitting the tips or rolling off the edges like you're seeing.

You MUST understand that the "scroll" that you see on the LS rocker where it contacts the valve tip runs out at about .550" lift, from there you're opening the valve with the tip end of the rocker!

When the rocker scroll is in contact with the valve tip the contact patch is fairly wide and the oil film is supporting it. Once the rocker gets out on the tip end, the contact patch gets very narrow. The oil film will not support the very narrow contact patch forever, and then eats up parts. This narrow contact patch is happening at the same time maximum spring pressure is happening, so that's a double whammy. Actually, there's a triple whammy because the rocker starts scrubbing after .550" lift, where it works like a rocking chair or gear mesh for the first .550" of lift, after that it scrubs.

For what it's worth, a LS7 rocker has more contact patch at .650" than a LS1/2/3/6 rocker has at .600"! If you do the math of a contact patch that is .020" X .200" that equals .004 sq in of area, at 471 lbs of spring pressure your resultant pressure is 117,750 PSI!

(I thought they would help keep things stable at higher RPMs).
You're better off to run softer ramp rates and less spring pressure, it may make just as much power, it will be stable, and it will be durable. I use 400 lbs as a maximum number for stock rockers.

And one more thing....when I pulled this motors top end off I noticed a odd wear pattern on just a few valve tips. About 3 or 4 valve tips had a wipe pattern that extended to the edge (outboard/exhaust) of the valve tip (it kind of rolled the edge a little).
You should have those tips ground at a minimum, and might need the valves replaced.
 

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Discussion Starter #18
Thanks Billyman and Brian T.

Hey Brian....so...if I run this setup will I have the same issues...here is what the new setup will consist of.

LSL/HUC 620ish/630ish
stock lifters ~ .065" preload
PRC .675's ~ 157lbs @ 1.800" & 471lbs @ 1.125"
Smith Bros. 3/8 x .049" 4130 pushrods

And FWIW, I'll be shifting this motor at 6800ish or where ever this ported 102 falls off at.

Thanks....and ofcourse the valves tips will be fixed or replaced.
 

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Discussion Starter #20
10-4....matter of fact the guy who bought the cam and pushrods wanted the springs but I told him I was hanging on to them....looks like he may be getting a call.

Could you PM me with details and price on the springs ??

One more thing...are the 3/8 pushrods over kill ? Maybe I should just stay with a 5/16" X .166"..??

Thanks....
 
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