Broken rocker stud

Broke a rocker stud

7/16" one with crower rockers and girdle. I have 260# on the seat.....

It popped it right of above the rocker at the bottom of the nut. Any ideas? why it would break..... I t was idleing while I was filling trans fluid and just started missing......

Broke a rocker stud

7/16" one with crower rockers and girdle. I have 260# on the seat.....

It popped it right of above the rocker at the bottom of the nut. Any ideas? why it would break..... I t was idleing while I was filling trans fluid and just started missing......

What brand of stud? Were they new when the rockers were installed? Can you post a picture of the broken stud? Sometimes the fracture tells a lot about the heat treating or material.

How many hours on the stud and rockers? How high do you turn the engine? What is the open spring load?

Joe Urban

ARP stud.

640 open ( if I remember correctly)

The fracture looks like it has lines across it side to side in a half moon shape, and it was a flat staright across where it broke.

4 passes, everything is brand new. Highest it has been is 7400

Can't get a pic right now.

ARP stud.

640 open ( if I remember correctly)

The fracture looks like it has lines across it side to side in a half moon shape, and it was a flat staright across where it broke.

4 passes, everything is brand new. Highest it has been is 7400

Can't get a pic right now.

I would call ARP and ask them if they will analyze the failure if you send the stud back. Tell them the spring loads you are running and what kind of rockers. Ask them if there is a way to tell what batch or lot your stud came from. Tell them you are concerned about the rest of the studs in your heads. ARP is a high class company. Their products rarely fail, at least in my experience, and the folks I hang with or meet in Motor City.

Try these numbers. 800.826.3045 or 805.339.2200 Ask for tech support.

From what you said above, there could be improper heat treatment or perhaps a material defect. There is also a possibility that something is binding in the valvetrain.

Joe Urban

Was it a Crower girdle? If the girdle was mis-machined it can tweak the studs and cause failure.

Most common problems as mentioned above are from the girdle loading the studs. A lot of head manufacturers move their studs around. On any engine with spring pressure like what you have above, I would only use shaft rockers. In the end something like a Jesel Sportsman isn't much more $$ and the reliability is 100% better.

I would advise against the Jesel Sportsman series for ANY application, the are cheaply machined and they have cheap parts in them compared to JESEL's premium lines. If I knew how to get pictures off my camera (other than taking them to Wally World) I would show you several examples of broken Jesel sportsman rockers.

Send the stud back to ARP, sounds like a bad batch of heat treat.

You can't catch a break, I think YOU could break a cannon ball in a sandbox!

I think it has to be the girdle. When I set the lash its fine then I tighten the girdle its off again......some get tighter some get loose.

I can't afford anything else right now.