Broken rocker stud. wrong length pushrods?

[zrayr]

anytime you have guide plates, you need hardened push rods. As far breaking a rocker stud, I had one break after a new rebuild, it happens, and sometimes nothing else "caused" it. Could've just been a defective rocker stud.

Z. Ray

[DAVID GAGNARD]

I would also get rid of those pushrods and get a set of one-peice pushrods......After about 2,000 miles my engine developed a miss and after pulling the valve covers, I found 3 pushrods DID NOT have the little pressed-in balls on the ends anymore!!!!!!!!!!!!!! Since then, I've never trusted those type pushrods and will only use one-piece pushrods...........

David

[Rick Parker]

How many threads are captured by the adjusting nuts? I would recheck the length of your pushrods. It looks as if they are too long causing the static position of the rocker arm to be too high on the end with the pushrod. As the cam raises the rocker arm up, and it starts to "Rock", the arc that the upper cup travels through causes the pushrod to move in the guide plate toward the stud. As the limit of travel was reached (as it pivoted) and the cam continued to force the rocker arm, it forced the pushrod into the bottom of the slot as it was bending it over the edge of the guide plate. It reached the travel limit and with the stud in severe tension it popped. Get the ARP studs and check the pushrods.

This situation gets worse if you are using 1.7 ratio rocker arms.

[jbuchert]

My guess was not enough thread engagement. A lot of stress was applied to only a small portion or tip of the stud. That combined with the rocking motion and high spring rate it was only a matter of time.

[Gaz64]

I agree with the other boys comments, you definately have a binding issue, be it pushrod to head, pushrod to guideplate, coil bind, retainer to guide etc.

If one has done this, the fault will be with the other 15 as well.

If that pattern on your valve stems is a wear mark, I'd be concerned and fitting a set of hardened lash caps, roller rocker wheels are harder than valve stems.
You'll be resetting your lifter preload more often until you discover the valve stems peened over.

When you built the engine, did you use a solid lifter for rocker geometry check?
Did you rotate the engine while checking the clearances within the rocker itself, to stud, to pushrod, to retainer, retainer to guide/seal, pushrod to head, pushrod to guideplate?
Everyone of these clearances is critical, if one of these is too small or zero, the inevitable will occur.

You must run hardened pushrods with hardened guideplates.