Cracked rocker arm

This was on a motor that exploded.
Only one of the arms has a visible crack.

Should I consider the rest of them toast or just replace the one that is cracked. One concern I had was the weight. I don't think there could be that much difference, but I dont know so I figured I would ask. would I be able to use any roller rocker or would I have to match it with the same make?

thanks

 

I'd buy a new set. Hard to tell from the pictures, but those don't look like top of the line roller rockers.

Don

 

No way to tell. I broke one exhaust rocker in the first week of a new build, replaced it and never broke another in ten years I drove it hard.

However, new rockers are so affordable, why not spring for the goodest new ones.

jack vines

 

If that's on a race engine, defenetly, aluminum will fatigue very quickly as compared to steel especially if you have high spring pressure and lift. Anyways, cheaper to replace a set of arms rather than the entire to engine

 

Ah heck.....just 'put some "JB-weld"
on the crack and it'll be as good as
new!!!
--------
Mart3406
==================

 

Think I'd lose these and buy another set---safer in the long run.

 

I would replace the set...Hard to put a price on aggravation if another one brakes.

 

Ditch them...stay away from cheapos such as ProComp, etc...... this is what happens to them....
Tom

 

Odd that it cracked on the compressed side. Probably bad casting. As others said, new is cheaper in the long run.

 

Apples to apples, aluminum does have less fatigue life than steel. And, high loads can cause rocker arms to fail. But, things like valve float and spring harmonics can break even good parts. Unfortunately, it's hard for the average person to know. If you are using some hot profile from the '60s, that might be your problem. If you are using something that has been found to be generally reliable it's probably either cheap rockers or LOTS of miles.

 

About 20 years ago, I built a 350 Chevy for my boat with "el cheapo" aluminum roller rockers. The first year, one broke. I replaced it with a stamped steel one to finish out the season. I intended to replace it over the winter. I even went so far as to source the proper single roller rocker. Then I forgot all about it. Now that you bring it up, it would seem the the person who said it was a casting flaw is probably right, and the difference in weight doesn't seem to have come into play, either. I no longer have the boat, but know the guy who bought it. It is still running great. He was a ltle pissed when he pulled the rocker covers, though.

 

thanks for the heads up, I think that I will just s**** the rest.

 

My first thought was that it cracked in a place where it should never be under tension. I don't like the idea of a cast body but some of the high end manufacturers are using cast bodies now to cut machining costs. I'm sure that with good quality control, good castings can be made but is impossible to tell by looking at the part after it is made.

I've seen a Harland Sharp rocker break in an engine that grenaded and we replaced it and used the others in another engine. Seeing how this one cracked would make me discard the rest and not use that same brand because I doubt the quality of the casting process they use. I'm sure some manufacturers have the castings made off site which makes it difficult to control quality.

 

Based on my quick ****ysis, the ID of where the fulcrum is is subjected to tensile "hoop stress".

Cheap casting = many voids = stress concentrations. IMHO that's why it cracked where it did.

 

I think I would opt for a new set. HRP

 

I think they are cheap too. I would not choose these again

 

If the bearing is pressed into the casting - then you have a hoop stress at the ID surface (ID of the casting). This is where the crack will initiate from.