8RT in a ‘36!
I have used my KD spark plug hole insert tools many times. The common 14 mm plug tools also work for putting a plug insert in the oil drain hole on Honda cars.
Any good parts store should have the K D insert kit. Put the insert on the spark plug and screw it into the head AFTER coating the insert with blue loc Tite
I just wasted two days trying to find Keen,Serts, Time Serts or whatever. I am not too crazy about Heli Coil.
I found what I needed at Thread Kits Company
Threadkits.com
310-897-1995 there in Carson, CA
Very easy place to Beal with, they have rivet Serts n other thread stuff too.
The Time Serts for bolts kit has a cutterthat you use after you drill out the old threads.it cuts a groove around the top of the hole. The inserts have a ridge or hat brim around the top of them so when you put the insert on the bolt looking insert driver you can Omnitel secret the insert in until the ridge bottoms out in the groove at the top of the hole leans the insert flush with th top of the hole.
When it stops turning you keep on twisting the driver a couple of turns which expands the bottom of the insert lock it in so it can never back out.
I don’t know if Time Sert’s spark pug holrepai kits have the lock in feature.
For plus I have only use KD, HeliCoil and KeenSert.