I keep breaking rocker studs. So far, I've broken 3. The first one I broke, I had pressed-in studs and had to replace the heads. Now I have sportsman II heads with screw-in studs. I broke another rocker stud at normal operating speeds (I didn't notice it when it happened, but realised it while in the parking lot. Happened between starting it, and driving around in a parking lot.) After replacing that one, I also put on a stud girdle. Third one broke yesterday, about 3 days after the second one broke at about 5200RPMs with a pop. All 3 studs that have broken are different.

World Products Sportsman II heads 72cc, SLP 51006 cam (about .500" lift), compcams magnum roller-tip rockers 1.52 (self-aligning), stock-length lingenfelter chrome moly push rods, and the springs are compcams springs but I don't know the number, upto .600" lift (came with the heads). I believe the pistons are stock-replacement (they are cast and slightly dished with 4 valve reliefs).

I don't know what's causing this. Please help before I run out of rocker studs.

The studs are 3/8", but I don't think I would be pulling enough lift or RPMs to break them if everything's working right.

 

ARP probably makes some rocker studs with 210,000 PSI tensile strength....I bet those would do the trick.

 

S2 heads... those come with guide plates, correct? There's your problem right there. You have 2 systems attempting to locate the rockers on the valves, and they want to put the rockers in slightly different places. This is clearly impossible. Something has to give, sooner or later; in your case, it's the studs.

Show us a pic of your valve train.

Look at the rockers on the studs that have broken, see if there's any wear on the sides of the rails; look at the valve stem tips, see if there's wear there; check for valve guide wear. All of those things will get stressed by that, in addition to the push rods, the rockers themselves, the studs, and the guide plates.

 

No Kidding!
Self aligning rockers with guide plates:nono:
I feel sorry for your valve train, it's probably been stressed in ways that are only beginning to show right now.
The magnum rockers are the ones with the pivot ball, right.
A possible solution could be to simply remove the guide plates and while it's torn down, get a new set of studs.
But a thorough inspection of everything is in order as well.
Also considering that there's been some unusual stress on most of the parts, I'd get a set of screens and some magnets to put in your heads and lifter valley to catch any debris, should something else fail later on.

That would be the cheap fix.
A perfectionist would suggest replacing a lot more parts than what I just mentioned.

Good Luck

 

I removed the guideplates before I put the self-aligning rockers on. I had the pressed-in studs on the previous heads, thus had self-aligning rockers, so when I got the sportsman II's, i took off the guideplates and put on the self-aligning rockers.

I do not have a digital camera. There is no visible wear to the valve stem tip, or any portion of the rocker/rocker slot nor is there any damage apparent on the rocker stud (besides where it's sheared in half)

 

Are you sure that those rockers have enough pivot to support .500 lift? If not that will stress the studs.

 

I think they're good to .750"? CompCams Magnum roller-tipped rockers. The slot is huge compared to OEM rockers. There would be wear marks on the rocker slot and/or the rocker stud where it was hitting. There is no visible sign of wear.

 

Could be the rocker geometry is wrong.
With a pushrod that's the incorrect length, the end of the slot could possibly contact the stud no matter how long the slot is.
I'm not sure what the correct clearance is... probably .060 or something close to that.
But that would be checked at the highest lift - Look under the rocker where the slot is - A piece of bent wire or a drill bit can be used to measure that clearance.
Might as well check it on the opposite side with the valve closed too.

 

I think Streetiron may have it. Did you use a pushrod length checker to determin you needed stock length?