Broken Rocker

TheMealOnWheels said:

To be fair, it's not new to see aluminum rockers fail on ls motors in street applications, regardless of Rev limit setting. Yella terras had a documented failure history on ls1tech. I had yella terras on a 383 and preemptively replaced them when I learned of the issue. If you don't want to deal with this, the oem rocker is a surprisingly durable substitute with a trunnion upgrade.

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Aluminum does not have anywhere near the fatigue life of alloy steel. Cumulative load cycles is the limiting parameter, whether idling at a light, driving on the highway, or at red line on the track. Where the lower mass of aluminum is a benefit in race engine applications, the rockers need to be replaced every year or two. I notice that in drag racing that is personally funded, such as NMRA and NMCA, there is a trend back to steel rockers even for very high-lift, solid lifter applications. With finite element analysis design tools in wide use, a steel rocker can be designed to have adequate strength with surprisingly little weight penalty compared to aluminum.

phonious said:

View attachment 304067 View attachment 304068
Here is the damage, I am working with someone from Yella Terra to try to get a replacement.

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IMO you should replace all of the rocker arms. This is the first failure, but the rest have the same number of stress cycles.