Over-sized Spark Plug Hole

[Winter]

Hello again.
A minor surprise has popped-up after sourcing the correct plug for my 1965 ('66?) 160.
The plug thread measures roughly 12.5 mm (12.7 according to NGK), but the hole measures at least 15 mm.
For the most part the threads are in tact in the hole and the question becomes whether or not there is an over-sized equivalent to the Champion L-78 (which was cross referenced for the B7HS) or will an insert be required?

All the Best (and I hope everyone is riding this weekend, at least here in the Toronto, Ontario Canada area)
Andrew

[Jordan]

It might be that a thread repair adaptor was fitted, now missing?

[Winter]

Yes, could be. It arrived without a plug and no telling what was done or what the original insert was.
I suppose I need to check the dims of the "big-sert" and see if that is an option.
Thanks for looking in.

A

[Eldert]

Hi Andrew

the thread of the B7HS is 14 mm , the lengt of the thread is 12.7 mm so maybe you can get away with a timesert and if that wont work you could try a bigsert

Eldert

[Winter]

Thanks guys.
I have found a quality machinist who works on Porsche here in town. He's agreed to check it out.
Still a bit of a "dome scratcher" though.... I believe the term for the PO might be "bodger"?

All the Best,
Andrew