Thanks, guys. The cast aluminum grade is unknown- done in CA in the mid '80s. I'm not enthusiastic about helicoiling 20 big. perfectly good holes just on a whim. I'll go with ARP's stud length recommendation.
Guys, I have a very basic question: in a bolted joint, does using a threaded stud beyond a certain length gain me anything in strength? Specifically, I have an aluminum racing engine block with threaded stud holes 2.7" deep for 1/2-13 SAE studs holding the aluminum heads. ARP doesn't make such a...