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I recently needed to replace the heads on my 1966 289 engine because one of the heads had cracked just above the front lower head bolt near the #1 cylinder. I bought some rebuilt replacement heads with the same C6 0E casting numbers from a reputable supplier. Immediately after installing them I broke a #3 exhaust valve rocker arm. I also found that 6 of the 8 exhaust valve push rods were bent. During the investigation into why I thought this may have occurred I found the source of this problem to be the fact the valve springs were in a coil binding situation when the valve was fully open. It turns out when the replacement cylinder head supplier rebuilt these heads the valve spring assembled height he used was 1.55 inches – significantly lower than 1.75 to 1.78 inches which is what is specified in 1966 Ford Mustang shop manual. I also measured a number of the valve springs and found they went into coil binding at about 1.17 inches. This means the total valve travel before spring coil binding is about 0.38 inches. Since the specified exhaust valve lift is 0.38 inches this confirmed my suspicion that it was truly spring coil binding that created this problem. And yes, I did check the valve to piston clearance and found it to be much greater than specified 0.082 to 0.152 inches, so I know the problem was not associated with the valve hitting the piston. When I contacted company I bought these heads from they indicated these were stock replacement valves and could not offer any explanation why there was a problem.

Has anyone else had any similar experiences?
 

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valves

Drag, do your exhaust valves have rotators under the retainers ? If youhave rotators and your springs aren't intended for them, you'd have much less room for spring travel than you are supposed to....sounds like a mis-match of parts to me. LSG
 
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