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Old 06-22-2019, 12:16 PM
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Texasdoc Texasdoc is offline
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Join Date: Feb 2012
Location: Keller, TX
Cobra Make, Engine: Lonestar Classics LS427. Self-built 408W, AFR 195 heads, Performer RPM Intake, Quick Fuel 750, 407rwhp, 479rwtq
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Default Loose rocker stud

Last week I was on the track. I was pushing pretty hard, not 100%, but more like 80%. On one lap, I was on light throttle in a turn, about to let someone pass when I heard a loud bang, bang, bang. The motor died over a few seconds.

I pulled off to the side of the track. After being towed back to the pits, I opened the valve cover and found the #5 exhaust rocker had jumped off the pushrod. Further disassembly showed that rocker stud had backed out, creating a loose pushrod guide and loose connection between the pushrod and rocker, allowing the rocker to skip off the pushrod. The pushrod was still straight, the pushrod guide still intact, and the rocker only had minimal scratches to the body where it was hitting the #5 intake rocker. The polylock was still locked to the rocker and the rocker to the stud.

I was able to reinstall everything and only missed one track session. Everything worked fine after that. I don't remember what I used on the exhaust stud threads. I know I used ptfe paste on the intake studs since they go into the intake runners, but don't remember what I used on the exhaust side. I think it was blue loctite. I am positive I torqued them as instructed.

Has this happened to anyone else? Any other suggestions on how to prevent this in the future? I'm not sure if a stud girdle would fit under my valve covers. Or do I just add this to my list of things to check every spring when I take it out of winter storage?
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