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Discussion Starter #1
These pictures are of my original 88K mile 289. The exhaust valve rocker arm stud on cylinder #3 has a groove worn in it from the rocker arm. The rocker arm was not perpendicular to the stud and the slot in the rocker arm was rubbing against the stud. The end of the valve stem is also worn at an angle from the tilting rocker arm.

Has anyone seen this before and if so do you know what caused it? I checked the push rod and it is not bent.



 

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Discussion Starter #2
I'm taking this engine to the machine shop tomorrow to have it rebuilt. The machinist I talked to said that this is not unusual and that he would replace the rocker arm stud and valve.
 

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Look at the slot in the head where the pushrod passes through the head. Is the slot wallowed out? Compare it to some of the others.

John
 

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Re: ocker arm stud wear

Happened to me twice.
First time, the stud had actually been installed at a tilt, like the leaning tower of Pisa! Somehow, the shop was able to reinstall it upright and it was fine.
On my current engine, it happened again, sawing through the stud. But everything appeared to be in alignment, otherwise, so I don't know the cause. So, I put in a fresh stud, been fine for 10 years. Maybe the valve tip is not square enough to the valve tip? I dunno. Whenever I hear valve clatter, it's the first place I look. Roller rockers should solve it, no ball to roll around on.
 

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Discussion Starter #5
John,

I looked carefully at the slot in the head that the pushrod goes through. It doesn't look any different than the rest of them.
 

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Re: ocker arm stud wear

BluEuc

The first thing that I thought of was that the pushrod, the stud, and the valve stem were not in line with each other. I held a straight edge up to them and could not see any misalignment by eye. Of course they could still be out of alignment by a small amount.

I know that later models use "rail type" rocker arms which locate off of the tip of the valve stem. I wonder if the wear we have seen was recognized as a design problem and that is why the rocker arms were redesigned.

And yes, this rocker arm was clattering.
 

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The machinist spotted the same wear on one of my rocker arm studs on my '66 289. No explanation why that stud and rocker wore or why none of the others wore. I had it replaced during my rebuild and put on a new set of rockers.
 
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