Originally Posted by S10 Racer
Rule of thumb for minimum thread engagement is the diameter of a stud or bolt. If you have 3/8" studs, the minimum thread engagement is 3/8", 7/16" studs is 7/16" engagement and so on. In your case though, you need a minimum of 1/8" thread above the top of the nut to allow the locking part of the nut to be into the threads of the studs. The stock nuts are a "stover" lock nut which is nothing more than a slightly deformed nut and threads towards the top of the nut. This deformed area needs to be engaged on the threads of the studs to be effective.
Sorry wasn't clear.
These are the rocker nuts I'm using:
COMP Cams/3/8 in. High Energy polylock rocker arm adjusting nut (4604-1) | | AutoZone.com