The SuperTrapp muffler is a tunable muffler, but because it didn't make enough noise for the previous owner, he swapped out the guts of the muffler and installed a pipe with a bolt in it so the exhaust sound would be louder. I think that might be why the horsepower is so low—it wasn't allowing the muffler to do the job it was designed to do.
Fortunately, I'm not interested at all in how the exhaust sounds, but rather how it performs and the role it plays in making horsepower. With that in mind, I ordered some new packing material from SuperTrapp and opened up the muffler so I could rebuild it and hopefully allow it to perform as intended and help the little hot rod make more horsepower.
Although he wasn't using it, he had kept the perforated tube and the tuning discs. All I needed was the packing material to wrap around the tube and re-insert into the muffler
It was a lot of material, but I eventually got it wrapped around tight enough so it would fit into the muffler. SuperTrapp suggested using masking tape to secure the packing material so you could insert it. They said it would burn off with the hot exhaust gas, but it wouldn't cause any problems or do any damage.
Adding or removing the end discs is how you tune the muffler. Fewer discs should make more torque and more discs should make more top-end horsepower. Using more discs might make the engine run a little lean, so will definitely need to consider that when we re-jet the carb. Looking at the spark plugs, she already appeared to be running a little lean, so with what we're doing this year, I'm sure we'll be adjusting that when we go back to the dyno.
I've only got until July before the test and tune to get everything done, break in the big bore kit, and be ready to run some test runs on the salt. It seems like a while away, but in reality, it won't be long before we'll be flying down the salt.