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Re: [T3] Stretching valve stems?

On the last set of heads I had on the Square, the had 60-70K on them when I
did a valve job.  #3 had been tightening up, and I found the seat had indeed
settled into the head, and the valve had mushed into the seat, so that the
contact surface on the valve and seat had increased.

I guess it was getting ready to break.

I still have this valve and could measure it if there is a steadfast spec
for stock length.  I cant remember if it was a VW valve or Aftermarket.... I
may still have used an aftermarket valve in 88 when these head were new.


> It is caused by the valve not hitting the seat square when it closes.
> And each time, the valve is bent a little micron or so. and then bent
> back maybe the next time. At the number of times the valve closes per
> minute when our engines are running at highway speeds, the metal starts
> to fatigue. As it fatigues, and the seat starts to get hammered. The
> valve settles into the seat, and due to the metal fatigue, the valve
> eventually breaks if not replaced.
> This is one reason I ALWAYS replace the exhaust valves, and the guides
> on any head I do, unless when I measure the guides they are found to be
> OK..

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