Rocker Stud Length Selection...

[DaveMcLain]

What is really the best way to determine what's needed in a rocker stud for a particular application with a stud mounted rocker?

When selecting rocker studs for a particular application how much of the threads should be inside of the hole in the trunion? It seems like the rocker should rest mostly on the shank of the stud and contact very few threads. Would it be better to have an adjuster that's relieved at the bottom to allow the trunion to contact exclusively on the shank of the stud? Does it make no difference? How much thread is really needed inside of the adjuster? If it is screwed in more than three of four threads is that really enough? I can't say that I've ever seen any real info on this subject... Any ideas?

[MadBill]

As a general rule, one diameter is the minimum thread engagement for a fastener. 1.5 is safer. I'd say as long as some part of the stud shoulder extends into the trunnion bore it will preclude the largely-theoretical possibility of the assembly 'walking around' on the looser fit of the threads. (Many trunnions are counter-bored on the top to locate on the shank of the adjuster nut.)

If you want to be really precise re stud length, you could install a test stud, fix the valve at half lift via a tie wrap on the stem, position the rocker with the fulcrum- roller centerline at 90° to the valve stem then determine the required stud length to best support it in this location. (Pushrod length is a result, not an input in this process.)

[kirkwoodken]

There is a BBC stud which is 1/3/4" long on the bottom end and you can cut them to whatever length you deem necessary. Was used on factory aluminum heads. Can't remember the ARP part number. I have put shims on the studs to keep the rockers close to the stud fillet. Sometimes you can't do that for it messes with geometry. You probably know that. Knowing the 1 1/2 X diameter rule of thumb, I still like a lot of thread length in aluminum heads.