'41 120 Sparkplug gap question

Posted by Ozstatman On 2017/5/5 22:20:54
Been having trouble starting my '41 120 lately.

Fuel system was gone through recently, so I was fairly certain that wasn't the problem.

So, after another failed start attempt this morning, pulled the plugs and found the gaps on all were between .012"->.015"! They are new plugs, Champion UY6's, and were gapped @ .030" on installation. For reference, pictured below are the recommended gaps from the '41 Owners Manual and a Motors Manual. I also recall there were recent comments on Site about the gap being in the .025->.030" range.

My questions are:
1) Generally, why do plug gaps close?
2) Specifically, any thoughts as why mine would close up so much after only about 100 miles of driving on them?
3) Car is currently running rich, would this contribute to the gap closing up?

NOTE. When I cleaned and gapped the plugs this morning, set them @ .027", started the Coupe and went for an easy 20 mile drive. On many previous occasions, for a range of 110's and 120's I've been associated with, have usually used .028" and this has seemed to work well.

Further note - Click on photos for a larger AND clearer image.

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