I did it on my os 1.60 fx.I have two options one is to buy another head the other is to enlarge the plug hole make a tread m10 and screw in a plug... made of what? brass, alluminium or steel?

In Italy you may as well buy another head.

The alternative is a Heli-Coil thread insert at 1/4" X 32 thread size. The kits for these will cost more than a new head

Clarence Lee can fix the threads with a heli-coil for about $20. His address is is the classifieds of Model Aviation. You only need to send the head to him. His business is "Lee Custom Engines" 1-818-352-3766.

If you decide to go the plug route, use aluminum. You will have less trouble with it coming loose. If you drill and tapthe head, then throughly clean the oil from the threads.Cut the threads on a piece of aluminum, then under cut it just at the point the die is just starting to cut the stock. Clean all oil off this piece also. Chuck the threaded rod in the drill press and screw it in under power until the under cut snaps off. This will effectively weld the plug in place. You can now face it offon both sides and drill and tap for the plug. You will need to make a good jig to hold the head while you are screwing in the plug and breaking off the undercut. I would take that undercut down to about 3mm. This "welding" will only work aluminum on aluminum.Clean fresh metal on both surfaces is required for it to work.

If you could send it to Clarence Lee, that would be my first choice. I've had him repair a couple and he does very good work and has super fast turnaround time. I would guess it wouldn't take much longer than two weeks total. It took just five days ship to receive for him to do my last one.

Good luck with what ever method you decide to use.

Don

I would send the head to Clarence Lee Mfg for a Heli coil.

Go to Lee, I send a head to him, had the hilo-coil put in and was back in my hand in 9 days.I thought it was a new head when I looked at it. Great job.

I also had great service with a fast turnaround from Mr. Lee.

Use a piece of aluminum for the repair.

The Glow plug is 1/4" X 32 threads per inch. You will need a tap