On the non-taperd plugs,which side of the metal ring goes towards the head? Small diameter or large?

It really should not matter, but if the small diameter matches the plug body, then put the small diameter against the plug.

The larger diameter fits the outside plug diameter best...Ive heard small diameter to head. Havnt read anything if matters but wonder why its different on both sides-which leads me to believe it may matter.

Never paid attention, but look at a brand new plug in the package - I would assume (ass-u-me) that the manufacturer puts em on correctly. Would be interesting to know why the diff.

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That's a good question, I've always wondered myself. Usually the new plugs come in the package with the ring loose in the box, not attached. I always have put the large end towards the plug, small end towards the head, but never really did know for sure. I'll bet some of the "older" timers on here would know from the old days.

If you look closely at the ring the large diameter side is flat and the small side is a little rounded.The large diameter flat side goes toward the plug and small diameter rounded side goes toward the head. The rounded side is designed to crush slightly when tightened providing a tight seal around the head.