The NGK AS-6 shielded plugs I have removed from the w670 engine has a thread length of 8.46 mm to the crush washer but the threaded hole for the plug has a thread length of 14.41mm so the electrode of the plug is within the confines of the hole not protruding in to the combustion chamber ?
On the six w670 engines I have worked on all plugs have this shorter plug thread to head thread length!
Last edited by Mark Robinson; 11-02-22 at 22:07.
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