Breaking BBC rockers

[ZZ430]

I took over a 496 project from another shop.

One problem is I don't know exactly what I'm working with, as far as cam and valve train specs. All I know its a custom grind Comp Cams solid roller. It has Comp +.080 pushrods.

It has BMF 330 heads.

This engine has broken 3 Jesel "SS" shaft mounted rocker arms. All of them have been on the exhaust, and they broke at very low RPM, at different times within the first 100 miles. They have all broken in the same part of the rocker.

I would have thought that if anything wasn't right with the geometry, the pushrods would bend first, but the rockers break instead.



I have eliminated coil bind, they have over .070 clearance.

I've called Jesel and they say that it's very rare to break them, but they did say that they have seen it happen if the shaft bolts were over torqued. They call for 22-27 ftlbs, and that is what I torqued them too.

Again, I didn't build the motor, just taking it over for a customer who had it done elsewhere. I don't know what they were torqued to originally.

Here are some pics.

Any suggestions? Thanks

[Bobby Schulz]

Friend of mine had the same problem with a batch of the same rockers on a BBC. Jesel made it right and replaced them but he broke 6 of the orginal set just like that. If I remember right I think the exhaust side broke first.

[ZZ430]

Thanks Bobby, that's what I'm thinking now, everything else checks out.

[ZZ430]

I have an update, Jesel called back and they had their metallurgy dept inspect the broken rockers we sent back.

They came to the conclusion that it was a problem on their end.

New rockers are on the way, no charge of course.

[Bobby Schulz]

Great news! Glad to hear that they are making it right but i have to say my faith in them is a little low now that I have seen this happen twice