Posted by Gus Pratt on May 08, 2002 at 15:39:13:
In Reply to: What to do with a 20J posted by Rick Denney on May 08, 2002 at 13:58:30:
I've often thought about this project also, and being the tightwad that I am, here is what I would do.
1. Rather then find a 4 valve cluster with the same bore, I'd purchase a used Conn 20K or fiberglas equivalent and use the 3 valve cluster, then add one rotary. I've never been a fan of the pinky, so I'd set it up as thumb operated with the rotor in the lead pipe. On a monster CC complete with beer tap, Jem Newell of Eugene has had success using a rotor after a 20K valve section, and setting it up with the spatula being operated with the pinky. One advantage with this idea is you then have spare parts. Things like valve caps, stems, buttons are the same. I think the pistons are the same except that the valve guides are different. You'd also have things like spare tuning slides. Also, with the exception of the 4th valve, it would look more authentic with short action valves.
2. As far as converting the bell, I'd find a 22" bell from an Eb sousaphone and fabricate (or have fabricated) the straight section. I had a friend who had a brass spinner fabricate the straight section once for this same project. The spinner didn't charge much, but found out it was a more difficult project then he originally thought it would be. I think Lee Stofer has fabricated the straight section before.
If you spend $500 for a beat up 20K or fiberglas, $500 for one rotor assembly, and $500 for an upright bell then you'd be well below the cost of the Holton or 3xJ series Conn.