Originally Posted by Walt Fricke (Post 11194925)

A bit crude, but you could add a washer.

Spark plug washers have some mystery to them. Some authorities say you should use new washers each time you have the plugs out. The regular plug washer is a crush washer. But I have never been able to find a source of these washers, and you have to cut the old ones off.

But for this (in a pinch), any copper or even aluminum washer of the right ID to slip over the threads should work.

This is the first time I have seen a reputable source show a reason to use one of the multiple electrode plugs. Looks like the right solution.