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broken rocker bolt

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Old Sep 10, 2007 | 04:17 PM
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Default broken rocker bolt

anyone know what would cause a rocker bolt to snap in half while driving? car has 69,000 miles on it and they werent over tightened. the big mystery is where the other half go. it didnt fall out when i opened the valve cover.
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Old Sep 10, 2007 | 04:32 PM
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its prolly in the oil pan or something.
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Old Sep 10, 2007 | 04:46 PM
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Do you have a photo of the broken end, it can help detect the failure mode (bending, tensile, etc.)? Improper preload can lead to bending, which could cause it to fail much like a bobby pin when you bend it back and forth.
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Old Sep 10, 2007 | 05:33 PM
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Could be in the oil pan. Never seen one break that was not being tightened or loosened.
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Old Sep 10, 2007 | 05:44 PM
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Over-rev?
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Old Sep 10, 2007 | 06:02 PM
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Even if the heads have been CNCed what route would the bolt take to find its' way to the pan. I can't think of a hole big enough for the bolt head to fit through.
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Old Sep 10, 2007 | 07:17 PM
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thats what im saying i have NO idea on how or what path the broken end would find its way to the oil pan or where ever it is if its inside the motor
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Old Sep 10, 2007 | 07:22 PM
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Originally Posted by vettenuts
Do you have a photo of the broken end, it can help detect the failure mode (bending, tensile, etc.)? Improper preload can lead to bending, which could cause it to fail much like a bobby pin when you bend it back and forth.

improper preload now theres an idea thats may shead some light on the subject. before the stud bolt it was believed by David (mighty mouse) i may be experiancing some improper preload do to the length of my pushrods which was causing the tapping noise that started after i installed my cam. i changed my pushrods to 7.425 the day before my rocker stud snapped. and no i dont have a photo of the broken end thats one mystery im still trying to figure out where it went since i cant think of any way it could find its way inside the motor where people are suggesting it is.
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Old Sep 10, 2007 | 08:28 PM
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One would think that if there was insufficient preload the installer would notice it when approaching zero lash. That's not likely in this case since the pushrods are longer than stock. Besides if one wasn't tight enough they would all be loose and that condition would surely have been caught during the torqueing sequence. I can see losing a valve retainer keeper in the head, but a rocker bolt. That's a stretch. It has to be in there somewhere. Clean your glasses and take another look.
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Old Sep 10, 2007 | 09:19 PM
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what im saying is that could it be possible that before i changed the pushrods i had stock size 7.4's i wasnt getting proper preload and over time the rocker stud just got weak from stress and snapped? and it just be weird luck that it breaks a day after me changing the pushrods
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Old Sep 11, 2007 | 05:15 AM
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From: Little Rhody
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Maybe I should clarify, sorry for the confusion, I meant bolt preload as opposed to lifter preload.
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