Yup, it's that infamous Exhaust Valve #3 again (that "6" is a misnomer). It's now back from the machine shop, with a freshly-cut valve face as part of a 5-angle valve job.

Now that the valve and cylinder head are nicely cleaned up, the valve is noticeably eccentric during rotation. This is most noticeable as the black crescent that appears on the edge of the valve when the "6" is rotated 90° clockwise. When tested, this valve pulls 0.5" of vacuum.

Exhaust Valve #3, post-valve-job


  • Is this visible lack of valve concentricity a cause for concern?
  • Would it cause any kind of damage or premature wear if it is pressed into service? It might be worth mentioning that I intend to use this for cylinder head for occasional drag racing.

1 Answer 1


The part you don't show on this exhaust valve which is much more important is how the lapping ring looks on the valve. If the ring which shows the lapping looks even all the way around on both the valve and on the seat, there really shouldn't be much to worry about. The seal is what's truly important here. If this area looks like it varies around the circumference of both, then I'd be worried. Besides, I'd think your machinist would have said something if there was a true issue with it. Remember, these are stock valves. They may not be perfect. As long as they seat and seal correctly, there really shouldn't be an issue. Strength is not going to be affected by this. I personally think there's less of a wobble there than it looks. I think the tone (color) difference from one side to the other exacerbates the look of the wobble as it goes around. If it were all the same tone, you'd hardly notice it (if at all).

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