something I have to deal with on my Tote Gote

[tomc]

Wanting to finally get started on the full resto of my '67 Gote model 680, one problem is with the threads in the exhaust port of the original 5HP Briggs . Evidently the original tapered pipe nipple, or a pipe tap has been threaded in too far, oversizing the hole. The threads still appear to be full and "sharp" but a replacement nipple will not stay tight, even with a lock nut. I'm trying to decide what to try next. Thread locker (loctite)? JB Weld? I don't want to change blocks because the block is the original and I very much want to keep it that way. I also don't want to use a flat muffler that bolts on because that certainly won't appear original. Any suggestions? Thanks.
As found.

 

[Rapidrob]

I would try to expand the muffler or nipple to meet the too large threads. You would need a tapered steel or aluminum mandrel in order to do this. Off the top of my head, the old "Wood Grenade" log slitter would work well in doing this. Or you could make one out of bar stock.
Heat the muffler or nipple up to chary red and drive in the taper expander and let it cool and try it for size in the engine.
I see no reason why this would not work.
I do not know of an adhesive that will take the heat of your engine other than a furnace cement but it is very brittle when cured.

 

[SAT]

Have you tried grinding the first several threads off a sacrificial pipe nipple? Your goal is to use the last 5-6 threads of the taper and not the middle area, which are now too small diameters.
Google National Pipe thread forms, it will clear-up my weak explanation.

 

[Richard Trotter]

Consider making a bolt-on exhaust. It will increase the flow...

 

[oldcarcbx]

A repair with a Helicoil may be another option

 

[Sport King Eric]

Another option is to weld a flange on the end of the muffler and take advantage of the 2 threaded holes around the exhaust port..

 

[FOMOGO]

Wanting to finally get started on the full resto of my '67 Gote model 680, one problem is with the threads in the exhaust port of the original 5HP Briggs . Evidently the original tapered pipe nipple, or a pipe tap has been threaded in too far, oversizing the hole. The threads still appear to be full and "sharp" but a replacement nipple will not stay tight, even with a lock nut. I'm trying to decide what to try next. Thread locker (loctite)? JB Weld? I don't want to change blocks because the block is the original and I very much want to keep it that way. I also don't want to use a flat muffler that bolts on because that certainly won't appear original. Any suggestions? Thanks.
As found.

Pipe threads are tapered. Like @SAT said, try cutting the first 2 or 3 or 4 threads off the pipe and tread it in again to see if that helps create a bite.