I would install the spark plug I intended to use and see if it
extends all the way into the threads in the head. If it does I wouldn't
worry about it. If it doesn't I'd be comparing the length of the
threads in the new head to the length in the stock head. Ideally, the
unthreaded plug tip should protrude slightly into the cumbustion
chamner, IME.
CR
John Caffrey wrote:
> Anyone have any complaints about the aluminum head manufactured by
> Pierce? Overall I think it is a nice piece, but there is one thing in
> particular I am not happy about. The spark plug hole was threaded all
> the way into the chamber leaving several exposed threads, and sharp
> edges where they break through the edge of the chamber. I bought a fully
> assembled head and hoped to use it after checking the seating, but now I
> want to machine away the exposed threads. Exposed threads in a
> combustion chamber has always been a no-no, but usually we're concerned
> with the steel threads of a protruding spark plug. Do all of these heads
> come this way or is mine a reject? Are sharp edges of aluminum not a
> potential detonation problem?
> John
> 67 MG Midget
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