Rage

Has anyone experienced break off of a Crane (or other) rocker arm stud at the interface plane between the rocker arm stud lock nut and the Crane roller rocker arm on a BBC (7/16-20 thread) where the rest of the valve train for that location is completely functional and in good working order? This was with hydraulic lifters, moderate load springs and lift (0.6") and 3000 rpm. There was ~200 hours total on the stud mostly cruise rpm but some WOT running up to 5800 rpm.

MER Performance

How much of the stud is being threaded into the nut?

Rage

1/2". It is a polylock nut.

Thunderstruck

Floating the valves can break a rocker arm stud. 5800 rpm is fairly high, what do you have for lifters, springs etc.

502ss

Incorrectly adjusted valves can break a stud also!

Rookie

I was breaking studs on the exhaust side years ago. (Manley and ARP) After I tore my heads down and reconditioned them, I found out that I had inner broken valve springs. Merc 425's, flat hydraulic lifters and mild cam 5200 RPMs.

Rage

Is that for solid lifters only or hydraulic lifters as well?

If hydraulic lifter can causee stud failure as well is it when the lifter is too loose or too tight that causes the stud to break?

Rage

Comp Cam CCA-929 springs and the stock 496HO roller lifters.

I run at 5500 - 5800 occasionally but mostly cruise at 2500 - 3000 rpm which was the speed I was running when the stud let go. Does the floating of the valves have to be occuring when the stud breaks or can the stud be damaged and break later at a lower rpm?

Rage

Thanks. I will check for that.

ezstriper

wrong lenth pushrods will cause the problem as well....Rob