I can't open the original pictures any longer but be sure that the allen-head set screw in the top is contacting the top of the stud near the top (within the hex area of the nut. If the studs are too short and don't extend up to the hex portion, all the stress of the set screw is being transmitted to the weakest part of the nut. Further, it may be counter-productive to tighten the set screws to an excessive degree. Breaking an ARP 7/16 stud is not an easy thing to do. 3/8 studs are less durable but even then, if they're breaking, there's something bad happening and the source of the problem needs to be identified. Not every thing that breaks on a high performance motor is the result of poorly made parts, Mexico and China notwithstanding.

 

I had issues.....
Got ARP's...
Issues gone!

 

i had a mechanic tell me to tighten them this way... i did it and about 1000 miles later i had one crack and come loose (valve cover kept it on)
then i re-adjusted them using same method 3000 later i had about five that had cracks in them. got a new set and quit using this method and no problem since. just use a long handled allen and it should be tight

7/16" ARP screw-in studs

 

I don't see your pictures

 

So ya'll recommend finding zero lash, setting the preload, then just tighten the allen nut snug?
-brandon

 

Since Bill indicated he was tightening them to 45 ft/lbs, I tightened all of mine to 42ft/lbs and still had 2 crack.
Yes, the cracks are well below the hex part, but the hex part is not very deep to begin with, maybe 3/8" at most, which I would not think is enough of the threads for the allen nuts.
A very good frind of mine that is a very good turbo Buick and LT1 mechanic told me that 42# is way too much, should be no more than about 30ft/lbs or as tight as a normal person can turn a regular size allen wrench.

The methods used above that are over tightening them, can be done and set the preload correctly..someone mentioned the lifter preload would be too much...but the way I had done it was to acheive a lifter preload of about 3/8 of a turn was to tighten the nut and allen set screw so that there was about 1/4 of a turn preload, then use the torque wrench to tighten the nut an additional 1/8 turn and acheive the desired torque setting..thus a total of 3/8 of a turn preload....but of course this results in too much stress on the rocker nut and causes it to crack....

So the correct way would be to turn the rocker nut to the desired preload...then llock it in place with the allen nut applying no more than 30ft/lb to the allen nut while holding the rocker nut in place so it does not turn.

Oh, sorry I had cleaned out my photo space and can't find the pics of the broken nuts to repost them, but there wasn't much to see except the rocker nuts cracked in half right at the bottom of where the set screw was, maybe a 1/4 inch down from the top...my set screws heads are just barely higher than the rocker nut top.

 

Do not tighten the allen nut tighter than about 30 ft/lbs, you should be able to break them loose by hand with not a lot of force..the rocker nuts that is.
Mark each rocker nut so you can easily see how much preload they have once the allen nut is tight...for cams with more than .525 lift HR I would say about a 1/4 to 1/2 turn is fine total preload after the set screw is tight.

 

this is the only way to do it, it is really ridiculous that someone would try to put 60# or even 42#. they dont need it they are just set screws

 

I have always adjusted the nut, then set the allen screw. Never had a problem. Cranking the whole thing further is overkill.

 

I'm sure everyone has a method for this, but 30 to 45 ft lbs on a polylock,
no wonder they are cracking. I have been going with 20 ft lbs on the nut
once the lock is set and have not had one come loose.

 

 

My car just broke it's fourth Valve Spring. this time it was the Manly springs. exhaust #5.

vacuum fluttering around 13 in hg. runs like its on 7 cylinders.

flumoxed.

 

I think all of us that have broke them have learned that lesson, but there are countless posts on this and other forums and "how to" websites that say "snug the set screw down, then turn the nut an additional 1/4 turn to "lock" it"..WHICH IS NOT THE PROPER WAY for anyone else reading this
But also not all polylocks are created equal...I have an old set from back in the 80's for 3/8 studs that are probably 3/8" thick below the hex head, waay thicker and heavier than these Comps.