# Poly locks



## foreevergoat (Oct 24, 2011)

Who uses poly locks to keep rockers adjusted? I have a 1965 GTO numbers matching YS block and heads all stock. Can someone recommend the best poly locks for this application also what are your thoughts on Melling 500574 chrome Molly push rods for my goat?


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## LATECH (Jul 18, 2018)

I use poly locks. The are on top of the BBC 7/16 studs I had installed.Keeps em adjusted.
Chrome moly pushrods? What ever for? 
You dont have that much stress on a stock 65 valve train with a stock cam


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## PontiacJim (Dec 29, 2012)

foreevergoat said:


> Who uses poly locks to keep rockers adjusted? I have a 1965 GTO numbers matching YS block and heads all stock. Can someone recommend the best poly locks for this application also what are your thoughts on Melling 500574 chrome Molly push rods for my goat?


Second question first - as *LATECH* pointed out, no need for the chrome moly pushrods if the engine is stock. If you need to "dial in" rocker arm geometry because of machine work or installing non-factory parts, then you may want to check to see that the pushrods are the correct length and the rocker arms are making an even contact pattern on the tops of the valve stems - then you might need new pushrods in the corrected length.

If the engine is stock, ie not rebuilt and/or heads/block machined, then the 3/8" stock nuts will be fine torqued down to 20-25 foot pounds. If you are having issues with the nuts backing off, it may be because they have been removed and re-installed a couple times and won't hold their torque.

If you simply want to install poly locks so as to "zero lash" the lifters and get a few more RPM's out of the engine before the lifters pump up, then add them.

You want a 3/8" x 24 thread poly lock. These come in 2 different lengths, long & short. I believe you may want the short so they do not hit the valve cover and allow the allen set screw to tighten correctly. Check out the 2 pics, the Mr Gasket 923G is the short and 920G the long.

The poly lock should tighten far enough down on the 3/8" rocker arm stud so the allen set screw is flush or just a hair higher with the top of the poly lock. The 3rd photo is a set screw sunk too deep into the poly lock. This means the ploy lock application is too long for the stud and they should have used the shorter version of the poly lock (or a longer rocker arm stud in the case of a 7/16" screw-in stud which comes in various lengths).

I found this explanation on how the poly lock should be screwed onto the rocker arm stud so you know if you have enough thread engagement or the poly lock is too short:

"Technically you should have 3/8 of engagement on a 3/8 stud and 7/16 engagement on a 7/16 stud. A 3/8 stud has a fine thread pitch of 24 threads per inch. That equals .042" per thread (per turn). Take 3/8, divide by .042 and you come up with almost 9 turns. That is "ideal". For a 7/16 stud it's .050" per thread (per turn) so take 7/16 and divide by .05 and you get 8-3/4 turns. Personally I've always used 6 turns as a bare minimum and never had any problems, ever, but my advice is to do it right."

The Pontiac rocker arm stud is 3/8" on the top above the rocker and 7/16" below. That transition area is the shoulder which the factory nut, formed to match that shoulder, torques down on. So the correct poly lock will have a base inside diameter of 7/16" so it can fit over the lower 7/16" diameter stud. If not, you won't be able to correctly tighten/adjust the poly lock down onto the rocker arm ball as the poly lock will stop/jam before it actually adjusts the rocker arm/ball for "zero lash". 

The Mr. Gasket poly locks are for example and a bit expensive. Butler Pontiac offers a less expensive set. You don't want to over tighten the poly lock/set screw as this can stip out the threads on the allen screw or crack the poly lock. One comment you may read in some of the posts, here and on other sites, is that the allen set screw needs a flat surface on the top of the rocker arm stud and the factory stud has a curvature to it - not flat. My experience has been that the times I have used them on factory studs, I have not had any issues. I believe the key is to kow how to correctly install the poly lock and tighten the allen screw so neither are over tightened. Sometimes this takes a little learning and you may hear ticking coming from under the valve cover - which means one of the poly locks has loosened up and the rocker arm is backing off. Don't wait until you have a rocker arm slip off and do damage, address the issue right away and re-adjust the valve and re-tighten the poly lock. Once set, you should not have to re-adjust the poly lock on hydraulic lifters. I have found that with solid lifters that I have had to check/re-adjust them a little more often - and it may have also been due to the higher RPM's I used to spin that engine.

That should hopefully answer your question.


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## foreevergoat (Oct 24, 2011)

PontiacJim said:


> Second question first - as *LATECH* pointed out, no need for the chrome moly pushrods if the engine is stock. If you need to "dial in" rocker arm geometry because of machine work or installing non-factory parts, then you may want to check to see that the pushrods are the correct length and the rocker arms are making an even contact pattern on the tops of the valve stems - then you might need new pushrods in the corrected length.
> 
> If the engine is stock, ie not rebuilt and/or heads/block machined, then the 3/8" stock nuts will be fine torqued down to 20-25 foot pounds. If you are having issues with the nuts backing off, it may be because they have been removed and re-installed a couple times and won't hold their torque.
> 
> ...


Thank you Jim for taking the time to help me out with this issue I appreciate your help.


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## Red Skeleton (Jul 2, 2019)

He


PontiacJim said:


> Second question first - as *LATECH* pointed out, no need for the chrome moly pushrods if the engine is stock. If you need to "dial in" rocker arm geometry because of machine work or installing non-factory parts, then you may want to check to see that the pushrods are the correct length and the rocker arms are making an even contact pattern on the tops of the valve stems - then you might need new pushrods in the corrected length.
> 
> If the engine is stock, ie not rebuilt and/or heads/block machined, then the 3/8" stock nuts will be fine torqued down to 20-25 foot pounds. If you are having issues with the nuts backing off, it may be because they have been removed and re-installed a couple times and won't hold their torque.
> 
> ...


Hi Jim, how do you change the rocker symmetry if it isn't dead center on the valve?


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## PontiacJim (Dec 29, 2012)

Red Skeleton said:


> He
> 
> Hi Jim, how do you change the rocker symmetry if it isn't dead center on the valve?


A solid lifter, an adjustable pushrod tool, Sharpie. Read this post which explains the process. 









Need pushrod length advise.


So I have been trying to figure my pushrod length. I purchased the lite valve springs and a adjustable push rod. Also using a home made solid lifter. I set my cam to the closed position set my adjustable rocker (stock rockers with 7/16 studs and poly locks) to zero lash. This is my results...




www.gtoforum.com


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