Timing Plug for 1948 Panhead - small problem

[harleygreg]

Hi - Enclosed is a photo of three plugs, one is the standard thread, 3/8" I believe (24tpi?), one is an oversize, 11/16" (16 tpi?) and neither fit the existing hole. The existing plug, also shown (top right) appears to have a different thread and is 21/32" thread diameter.

I can either tap the hole to fit the 11/16" plug, though I'm nervous about swarf getting in the case, or, perhaps, reduce the diameter of the oversize plug, by rethreading the timing plug.jpg plug to fit the existing hole.

Not being familiar with US threads, what would be the size/tpi of the existing hole?

Any other ideas?

Thanks

[T. Cotten]

5/8"-18tpi, Greg (if my memory still works...)

Beware many cases have been cracked with a tapered pipe plug like yours, so I strongly suggest a thread insert repair.

....Cotten
PS: An irregular hole can be difficult to seal with a hex plug, so I cut extra-thin PEEK repair seals for timing plugs, oil plugs, transmission plugs, etc.