busting poly locks
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busting poly locks

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    Senior Member vmaxed's Avatar
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    Default busting poly locks

    I got some poly locks that busted on the machined part where they meet the rocker arm. I have a good stud girdle studs are 1.75 long screw .355 into poly lock witch is less than .4375 7/16. Ordered some 2.1" studs 2.3 would leave .900 threads above rocker arm. Nut wouldn't tighten up on them. Any body else ever had this problem?
    "DON'T JUST TELL ME IT WON'T WORK TELL ME WHAT WILL"

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    Whose poly locks? What was the torque on the jam nut?
    Chris Straub
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    just a ski boat with bark Carnivalride's Avatar
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    Quote Originally Posted by vmaxed View Post
    I got some poly locks that busted on the machined part where they meet the rocker arm. I have a good stud girdle studs are 1.75 long screw .355 into poly lock witch is less than .4375 7/16. Ordered some 2.1" studs 2.3 would leave .900 threads above rocker arm. Nut wouldn't tighten up on them. Any body else ever had this problem?
    If you over torque that set screw they seem to break there from what I've seen. The set screw should need much if any torque since the girdle should keep the poly lock from turning.
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    LP-25.com Infomaniac's Avatar
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    See if the top of the stud is smooth or indented. Those things are cast and there are a lot of junk ones around. Tightening the poly lock against the set screw is asking for it.
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    Senior Member vmaxed's Avatar
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    Default locks

    CS don't know who made the first set came with Comp Cam setup. The set on it now came from Lunati. I tighten them with a t-handle surly I ain't over tightening them. Hope the .350 longer stud helps.
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    15#/ft is max you want to torque the set screw.
    Chris Straub
    Straub Technologies

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    Senior Member vmaxed's Avatar
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    Default woooo

    Dang I did not know that. New ARP studs should be here to day. Hope they are flat on top. Pain in the but to start from scratch. I run them twice if I have the girdle off.
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    www.highflowdynamics.com LakesOnly's Avatar
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    Quote Originally Posted by vmaxed View Post
    I got some poly locks that busted on the machined part where they meet the rocker arm. I have a good stud girdle studs are 1.75 long screw .355 into poly lock witch is less than .4375 7/16. Ordered some 2.1" studs 2.3 would leave .900 threads above rocker arm. Nut wouldn't tighten up on them. Any body else ever had this problem?
    Errr, are you sure the rocker arm trunnion isn't 180* out on the polylocks that are breaking down there? Also, make sure the rear of the rocker body is not contacting the polylock at full valve lift.

    I suggest you step up to a 1.900" stud for your valve train combo; the stud's thread depth into the polylock should be 1-1/2 times the stud diameter (not to suggest that this is part of your polylock failure issue).

    LO
    Last edited by LakesOnly; 11-07-2012 at 09:01 AM.
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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by vmaxed View Post
    I got some poly locks that busted on the machined part where they meet the rocker arm. I have a good stud girdle studs are 1.75 long screw .355 into poly lock witch is less than .4375 7/16. Ordered some 2.1" studs 2.3 would leave .900 threads above rocker arm. Nut wouldn't tighten up on them. Any body else ever had this problem?
    no

  12. #10
    Senior Member SuperJet's Avatar
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    Quote Originally Posted by cstraub View Post
    15#/ft is max you want to torque the set screw.
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    Default Busting, or splitting??

    Quote Originally Posted by LakesOnly View Post
    Errr, are you sure the rocker arm trunnion isn't 180* out on the polylocks that are breaking down there? Also, make sure the rear of the rocker body is not contacting the polylock at full valve lift.

    I suggest you step up to a 1.900" stud for your valve train combo; the stud's thread depth into the polylock should be 1-1/2 times the stud diameter (not to suggest that this is part of your polylock failure issue).

    LO
    My first thought as well... The only ones I've seen fail were tightened against the rounded portion of the trunnion, and they were split open rather than actually broken. If you're breaking them to the point of pieces falling off and they're tightened against the counterbore correctly, I'd lean towards them being defective. Maybe over heat treated to the point of being brittle?? Hopefully the ARPs will solve your problem, but look things over carefully for solid metal to metal contact at full lift, and remember, the springs and valves are really dancing around during operation. (a slow motion video will scare you to death when you see what is really happening to your valve train)....
    Ray
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    Senior Member vmaxed's Avatar
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    Default we will see

    Put the 2.1" studs in last night. I now have over .550 of thread sticking through the rocker arm. The old ones hah .350 all the material inside the rocker was threaded except about .100. Five of them were marred and wouldn't pull through the rocker. One was even bent. Now all but about .200 of the stud in the rocker is the smooth boss. I also made sure I didn't over tighten the jam. Everything seems to be friendly now.
    "DON'T JUST TELL ME IT WON'T WORK TELL ME WHAT WILL"

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    Are all you Arki guys like a Bull in a China Shop

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