To tap or not to tap?

If you're concerned about the value to a collector, you should probably go with the strap on muffler. If you just think you might sell it to another pilot, drilling it will only hurt the value if you mess up. I'm fortunate to have a friend who's a machinist and race car fabricator. He has tools and clamps to hold everything properly, and he is very skilled at using them. He's fascinated by our little engines and would do something like this job for me and would refuse to take a penny. Of course, when I had my race car, anything he did on it was "work" and that's never free.

Carrell

But is it worth worrying about the value?

To me it's just another engine, but that may only be because I'm not familiar with it, so I'd have my friend drill and tap it for the bolt on muffler. It's a preference based on nothing as I have no experience with strap on mufflers.

Get the strap on!

This engine has plenty of meat to drill the taps. As I said it is almost a copy of the Webra, including the large area to each side of the exhaust port. I found someone with a good drill press, so I will order the bolt on.