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I have a Cer. 601 and MW 45, thinking about having them converted to short stroke pistons. Would like some input on this as to about how much and if it is worth it. Thanks, T

Just one remark first:
- if it ain´t broke, don´t fix it.
Why mess with perfectly functional horns when others with piston valves are out there for you to buy / trade in?
Advantages of this approach:
- neither horns nor chops will experience down-time
- you might make happy someone else who´s looking for rotary horns
- you don´t risk screwing the horns´ intonation in the process

Disadvantages: your tuba-tech will not have hours worth of work.

So what is YOUR initial motivation to switch valve systems on your horns ?

Do you have a couple of short-action piston valve clusters? If not, where do you expect to find them? I don't think they are made any more. You can salvage them from Conn sousaphones, but only with 3 valves. You can get top-action valve clusters, sometimes with 4 valves from Conn 2XJs. But four-valve front-action clusters are practically non-existent. That's problem #1.
Problem #2 is that you would have to change the leadpipe and main tuning slide configuration to accommodate the new valve section. All of that is doable, but not easy. Doing it right and making it look good would be very expensive. Doing it with parts from the junk pile would leave you with a horn that looks like a junk pile. But it MIGHT play well.

If you can obtain the right piston valve set I would suggest installing it first on a junk tuba, just for practice. You could sell the old rotary valve section on Ebay for about as much as you paid for the whole tuba.

Thanks for the info.

If you are just trying to "open up" the horn, you can have the rotor ports "scooped" or enlarged on the Cervenys - many people including Don Harry and Jay Bertolet have had this done. The 45 should not require this. Perhaps a mouthpiece with a bigger backbore would be a cheaper and quicker alternative to change the blow. I am sure that there are a few 45SLP players who would be happy to trade for your rotary 45 - the SLP seems to have a relatively short honeymoon with many.

Try using a Mike Finn 4 on the 45S. I use it on mine, and I'll never have another problem with my tuba.

It may be worth a trip to your repair technician to see what he recommends doing on the tubas to help open them up. If you need help findind one, let me know.