chawin

Hi Guys,

Ive done lots of research and have not found a definitive answer. I am using comp's Pushrod length checker for this.

The part I am confused on is I was instructed to set the rocker to hand tight on the bolt. Then find the the push rods length with the checker for zero lash and then add .050 for pre load. (I want to set pre load at .050) so lets say I come up with 7.350 on the checker and then add .050 for pre load which would equal I want a 7.400 length pushrod...Correct??

Where I get confused is the rocker is only hand tight and with the way I understand it every turn on the rocker bolt from hand tight equals .047 of preload. Well lets say like above I already added in preload to get my 7.400 final length but then it takes me 1 turn on the rocker bolt to achieve 22 ft/lb of torque on the rocker bolt so now my preload will be .097 is that correct???

Or when checking with the push rod checker should I Torque the rocker to 22 ft/lb and then find zero lash and then add my desired .050?? or do I find zero lash at hand tight on the rocker bolt and still add my desired .050 preload then tighten the rocker bolt and I will still get my desired .050?

Basically do I use the checker at 22ft/lb on the rocker or use it at hand tight then add my pre load? I want .050 not .047+. I know there are other ways of doing it such as what vettenuts has posted but id like to use the PR checker I purchased.

Tainted

iTrader: (9)

get the bolt finger tight.

every turn to the 22ft lbs is .047

so you take that number, plus your pushrod length, and add your preload. if its not enough adjust the length in or out.

7.350 length to start
+1.5 turns = .0705
+.050 preload
= 7.4705

just an example

chawin

Ok, So lets say my zero lash is at 7.350 finger tight on the rocker bolt and I only want .050 preload on my lifters but it take 1.5 turns to get to 22 ft/lb which in turn is .0705 pre load... then since the 1.5 turns satisfies my .050 preload that I want for the lifters then I should not add in the .050 to my 7.350 PR length. Correct? and I should choose 7.350 PR length since the 1.5 turns of the rocker bolt satisfies my .050 preload right?

Atomic

iTrader: (37)

That bolt turn method is bullshit at best. You have the length tool, use it.

Tighten the rocker so its to 22ftlbs, adjust length checker so it takes up all the slack but doesnt compress the lifter. That is your zero-lash measurement. Add whatever preload you want to that number to get the length you need.

smws6ta

iTrader: (5)

what lifter are you using? LS7's have a preload of 0.075


Here's the formula for using the checker.

Every turn = 0.050"

So if you have 9 turns you multiply the 0.050, like so:

9 turns x 0.050" + 0.45" + 6.8" (total length of checker bottom out) = 7.25" + preload of lifter (in this case LS7) 0.075" = 7.325"


How to use get zero lash with the checker:

with the rocker off and push rod removed I start out around 9 full turns, insert the checker, now place the rocker in position and hand turn the bolt down snug. Do not torque. Now push on either end of the rocker and listen for any tapping. If you have some add one more turn to the checker, if no tapping back off one turn, and check again for tapping. If you get to where you have/have not tapping on one full turn in either direction try a half turn. This will fine tune it. Now once you got to were you have no tapping and the rocker sits on it without tightening it down to sit on the "pedestal" (not sure what to call it.) You are now at "zero lash"

Now remove the rocker carefully pull out the checker and while turning it back down count how many full turns it takes to bottom out. Add any half turns and this is you first number in the formula above.

Tainted

iTrader: (9)

zero lash - 7.350
1.5 turns = .0705
add in your preload of .050

you need a 7.4705 but they dont make them in such an odd size so you would want a 7.45 or 7.50

someone correct me if im wrong here because this is how i plan on doing mine

Ryan@BallisticSpeedParts

iTrader: (3)

I couldn't agree more...forget the bolt turn method. You'll have to remove the checker and adjust the length a few times (go in half turn increments) until you find the sweet spot where there is no more slack between the lifter and the rocker, that will be your zero lash. Then add your .050" of preload (we run about .030") to the length of your checker and that will be the length of the pushrod you will want.

chawin

Thank you so much for the advice everyone. I was getting confused if I was supposed to use the checker with the rocker bolt torqued down to the 22ft/lb or not and many people have said do it just hand tight and also to do it at torqued down specs so I wasnt sure which way to do it. It has only made sense to me to do it with the rocker torqued down and then just add my pre load to that but then other posters add in that equation of doing it hand tight then every turn of the rocker bolt equals X amount of pre load which I agree with but dont understand why guys wouldnt use the checker at torqued down specs. Looks like I will be checking length at 22 ft/lb and finding zero lash then adding my .050 pre load to the Ls7 lifters.

chawin

Does anyone disagree that I should not be measuring it with my rocker torqued down?

I just do not understand why I would check it without the rocker torqued down because then pre load on the lifter is getting doubled when I add the pre load into the PR length and then add additional pre load with torquing down the rocker.

mcdonald77

iTrader: (21)

measure it torqued down. You might have to unbolt it a few times because its hard to turn the tool in tight space. Remember to untwist the tool only enough so that there is no slack. The lifter should not be compressed at all yet the rocker should be a zero lash (no up and down play betweem the rocker arm and vavle tip)

I've taken advice from atomic and he knows what he is talking about.

vettenuts

iTrader: (4)

You can torque it down, I usually put a wrench on it and snug it down to keep from loading the aluminum threads multiple times. There are several posts in this thread that I can't figure out what the poster is doing.

Basically, get the rocker tightened down. Make your measurement to zero lash. Add the preload. The only turns being counted are on the pushrod.

vettenuts

iTrader: (4)

Huh??? Not sure what you are doing. Is the 1.5 turns on the adjustable pushrod?

gagliano7

The 1.5 turns is the amount it takes to torque down the bolt on the rocker arm. Torque down rocker adjust pushrod to zero lash and then add your preload and that will be your pushrod length.

Tainted

iTrader: (9)

Lemme see if I got this right, and this is just purely an example.

Pushrod length checker all the way out to say 7.350
1.5 turns = .0705
add in preload of .050

that nets you a 7.4705 or 7.45/7.50 pushrod correct?

vettenuts

iTrader: (4)

Don't follow. With no pushrod in there it should take about 1/3 turn to tighten the bolt from finger tight to 22 lb-ft. If it takes more then that the pushrod is depressing the lifter plunger, which you don't want to do when measuring.

Exidous

iTrader: (11)

What Atomic said is 100% correct. Torque to 22f/lb and measure with the checker snug at best. Add preload and there's your length.

Making it finger tight and counting the turns is for folks without the checker. You go finger tight. Count the turns to 22ft/lb. 1 turn is .047". Depending on the lifters you have will determine how many turns you want. Never more than two turns for any lifters that I can think of. Usually between .75 and 1.5 turns.

Either way the length checker is the best way to do it. If you have it, use it and completely forget the turn method.

dr_whigham

iTrader: (49)

Well I had the checker when I did mine and sold it. I found it to be a LOT easier to get the cam on the base circle, throw in a stock PR, get to zero lash, mark the bolt head, and count the turns.

One full turn for me to get to 22ft lbs.

chawin

Perfect, I got the correct answer... I was just getting answers from even people at TSP where they were mixing the turn method with the PR checker method and thats when I got confused and none of it started to make any sense to me logically. Thank you for the replies and finally have this figured out. Between work and family im hoping to have this thing assembled in the next week or two then to the tuner it goes. Im stuck though... I had the clutch pedal dropping to the floor issue when at high RPM so I also purchased a Tick to fix this but now I see that it could be that or many people say it could be the pressure plate also so Possibly considering picking up a monster clutch but that definitely wasnt in my budget... im already $2k over my original budget. The guy I bought it from said the clutch was 10k miles new and I believe him, cant believe the pressure plate would be giving me issues already.

ZeeOSix

I agree ... probably really no need to torque down to 22 ft-lbs every time. IMO, definitely want more torque on the rocker arm bolt than "hand tight", but why torque to 22 ft-lbs every time if you are tweaking the PR tool multiple times on the same valve?

The main GOAL is to make sure the rocker arm is down tight in it's resting place during the PR length measurement. Once the rocker arm is snugged down, adding more torque really isn't going to make the rocker arm seat down any more ... it's just going to stretch (pre-load) the rocker arm bolt and the aluminum threads.