Broken rocker stud

[Craig 94 TA GT]

Driving to work, I noticed a vibration that turned into a loud ticking, then banging. I got the car towed home and noticed the valve cover around #4 was bent upward. I pull the cover and notice that the rocker stud broke? They are Comp Cams 7/16" studs. I was just cruising at normal speeds and haven't got on the throttle in a while. I have maybe 10-15k on the studs.

What would cause a broken stud? I did have the lock nuts REALLY tight - probably over tight, but I didn't think that would cause the whole stud to fail. The rocker itself was adusted to 1/2 turn after 0 lash. I can post pictures later, but I was really shocked how this happened. The rocker, spring, and pushrod are all still ok at least.

[Joe 1320]

Driving to work, I noticed a vibration that turned into a loud ticking, then banging. I got the car towed home and noticed the valve cover around #4 was bent upward. I pull the cover and notice that the rocker stud broke? They are Comp Cams 7/16" studs. I was just cruising at normal speeds and haven't got on the throttle in a while. I have maybe 10-15k on the studs.

What would cause a broken stud? I did have the lock nuts REALLY tight - probably over tight, but I didn't think that would cause the whole stud to fail. The rocker itself was adusted to 1/2 turn after 0 lash. I can post pictures later, but I was really shocked how this happened. The rocker, spring, and pushrod are all still ok at least.

Likely an impurity that was trapped in the metal when it was made. Sometimes it fails quickly, other times it works for years and then simply lets go.

[Craig 94 TA GT]

Thanks Joe. I just wanted to make sure something else wasn't wrong, that caused this - or that I didn't improperly install something to cause this. I hope no other one will fail. I wonder if Comp Cams can address this directly, or if they'll just blame it on hard driving. Attached is the pic.

[97LT4SS]

Same thing happened in my '71 Z28 years ago...sometimes they just go. It does make quite an alarming sound.

[Joe 1320]

Same thing happened in my '71 Z28 years ago...sometimes they just go. It does make quite an alarming sound.

It gets your attention real quick doesn't it? Same thing happend to me with a brand new set of valvesprings. I only got maybe 50 miles and one let go.

[Black97]

It's hard to tell by the low quality and angle of the picture but as Joe mentioned it can be an imperfection in the material that eventually causes / starts a crack and then it fails.

Don't know if there's any heat treatment on these studs. If it's hardened too much it could crack easier too.

I used to work with a Metallurgist and he would get all excited to look at pieces like that and determining what happened.