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SETTING VALVE LASH: For decades good engine builders have had to blame other things while trying to figure out why their lash settings wouldn't stay locked down. Either they break the set screws in trying to torque them down too tightly, or the lash won't stay set because they weren't set tight enough. Most 7/16-20 high tensile fasteners can easily withstand 35 to 40+ lbs of torque, providing they are tightened down properly. Rocker arms using a lock nut on an adjusting screw (STAND MOUNT SYSTEMS), or rockers that have adjusters with an Allen set screw (STUD MOUNTED), can both benefit from a little known technique we call PRECEDING, which will assure they stay locked down, and avoid breaking the set screw in the process:

FIRST: With the set screw loose, use a boxed end wrench on the adjusting nut for stud mount rockers (or the Allen wrench used on the adjusting screw of the STAND mounted rockers), to set the valve lash as you normally would, being careful to take note of where the wrench points when you have the setting you want, as if it was an hour hand on a clock.

SECOND: Now rotate the same wrench counter-clockwise approximately 1/4 or 1/3 of a turn and stop. Then turn the SET SCREW CLOCKWISE to take up the free play, until it bottoms out (or the outer lock nut if STAND Mount rockers), remembering that your setting position is 1/4 or 1/3 of a turn loose.

THIRD: Lastly, now use BOTH hands to hold the Allen wrench and the boxed end wrench to turn BOTH the set screw and the adjusting nut (or adjusting screw and outer nut) simultaneously, tightening both to the same hour position your boxed end wrench was at when lash was set as you desired before locking down. In this final step, you are applying the locking torque in a way that tightens both the adjuster and the set screw (or the outer lock nut and adjusting screw if it's a STAND Mount system) so they preload within themselves EVENLY, without forcing unnecessary pressure to either one individually.

NOTE: The reason for the varying preload in the second step, where you back off between 1/4 and 1/3, is because all mechanics have a different "feel," and you will need to experiment to precisely stop on the exact spot which preloads to the desired lash setting you measured when there was no preload in the first step. After two or three tries, you'll get it and the remaining rockers will set quick and easy. Good luck.

Posted courtesy of Jim Miller.
 

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Great information. It's refreshing to have some tips and information in this section that don't revolve strictly around sales. Thanks for broadening the spectrum to encompass the entire valvetrain, as well. Hopefully we will get some great discussions pertaining to theory and application going. Thanks for your efforts.
 

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Discussion Starter #3
Your welcome! I hope to grow this forum over time and draw some more people in here that are interested in discussing valvetrain design, theory, etc. That's why I am going to be pretty firm in not allowing personal attacks, honest debate over differences of opinion is great but it needs to stay professional.

Again, I appreciate everyone that comes in here to participate!
 

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Don't want to seem stupid, but if you tighten the nut and set screw this way, what is the correct way to loosen them? Just loosen the set screw (won't it be tighter than crap?) or both at the same time?

I've had problems with this and honestly just want an answer. I've back out rocker studs trying to get a too tight nut loose!

Thanks dor the input.
 

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SETTING VALVE LASH: For decades good engine builders have had to blame other things while trying to figure out why their lash settings wouldn't stay locked down. Either they break the set screws in trying to torque them down too tightly, or the lash won't stay set because they weren't set tight enough. Most 7/16-20 high tensile fasteners can easily withstand 35 to 40+ lbs of torque, providing they are tightened down properly. Rocker arms using a lock nut on an adjusting screw (STAND MOUNT SYSTEMS), or rockers that have adjusters with an Allen set screw (STUD MOUNTED), can both benefit from a little known technique we call PRECEDING, which will assure they stay locked down, and avoid breaking the set screw in the process:

FIRST: With the set screw loose, use a boxed end wrench on the adjusting nut for stud mount rockers (or the Allen wrench used on the adjusting screw of the STAND mounted rockers), to set the valve lash as you normally would, being careful to take note of where the wrench points when you have the setting you want, as if it was an hour hand on a clock.

SECOND: Now rotate the same wrench counter-clockwise approximately 1/4 or 1/3 of a turn and stop. Then turn the SET SCREW CLOCKWISE to take up the free play, until it bottoms out (or the outer lock nut if STAND Mount rockers), remembering that your setting position is 1/4 or 1/3 of a turn loose.

THIRD: Lastly, now use BOTH hands to hold the Allen wrench and the boxed end wrench to turn BOTH the set screw and the adjusting nut (or adjusting screw and outer nut) simultaneously, tightening both to the same hour position your boxed end wrench was at when lash was set as you desired before locking down. In this final step, you are applying the locking torque in a way that tightens both the adjuster and the set screw (or the outer lock nut and adjusting screw if it's a STAND Mount system) so they preload within themselves EVENLY, without forcing unnecessary pressure to either one individually.

NOTE: The reason for the varying preload in the second step, where you back off between 1/4 and 1/3, is because all mechanics have a different "feel," and you will need to experiment to precisely stop on the exact spot which preloads to the desired lash setting you measured when there was no preload in the first step. After two or three tries, you'll get it and the remaining rockers will set quick and easy. Good luck.

Posted courtesy of Jim Miller.
Great Post! Ive just purchased the lsm tool with 20 foot pound torque feature.Does the above still apply when setting lash on my shaft mounted jesel system?
 

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Discussion Starter #7
Great Post! Ive just purchased the lsm tool with 20 foot pound torque feature.Does the above still apply when setting lash on my shaft mounted jesel system?
Yes, use the same process to tighten the adjuster.
 

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Thanks for posting ! I have done it this way for years and didn't realize it was a preferred method. It just always worked and I stuck with it.
 

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Great input
Thru my years I have come to find that even before you install your studs in the heads, the tops of the studs are not always square or flat and contributes to problems with valve adjustments. I've learned to face off the tops of the studs before installing them were as this aids the set screw to squarely seat into stud face and improves valve adjustments to be more stable and tighten easier. When turning or grinding don't take to much off to fast so that you don't get them hot and upset the heat treating. Works for me. Anyway I don't trust nobody you need to check stud tightness anyway so take out.

FOOD FOR THOUGHT Doug
 
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