Poly lock failure, causes

[racervette69]

What are the causes for a poly lock to break off at the top of the stud?

 

[TimAT]

Where did it, (the poly lock) break? Pictures would help-
IF the lock broke right under the flats, maybe a bad heat treat. If the stud broke right at the bottom of the lock, then maybe valve spring stack/bind.

 

[Twin_Turbo]

Rocker to hex interference

Sent from my GT-I9000 using Tapatalk

 

[68/70Vette]

Stud top not level, see the set screw compression on one side.?? Opposite of the last piece to turn loose. Didnt see that until I looked at the picture. Engine has about 10 hard hours on it. Dont know the brand.

I had an L88 clone engine (genuine L88 short block). I had to use poly locks on the rocker studs, to keep the rocker arms from walking loose. I was told that to install them, you had to have the tops of the studs lathed smooth and flat. I did and never again had a rocker arm get loose again.