Hi Dave
I have a mono CAV with a 342 4-barrel and 1 5/8 inch crossover headers into a stock CAV muffler. The stock muffler is a perforation and packing design and is quieter than the two baffle mufflers I tried (FlowMaster and SpinTech). I also tried a pair of SuperTrapps added to the stock CAV muffler.
All this was initial testing so don’t be too critical about the technical details, that will come in the future after I get some idea of the ballpark numbers. Basically I did not find a baffle design that was quieter AND potentially less restrictive.
All measurements were made with the db meter 3 feet high and 10 feet directly behind the muffler. I used a medium quality Radio Shack brand meter set to the A-Scale. I also borrowed two brands of baffle mufflers to test but I cannot find the actual numbers I recorded (how convenient). Nevertheless, both brands of baffle mufflers were VERY noticeably louder than the stock CAV muffler so I returned them to the owner. The mufflers tested are listed below. I concluded that the stock CAV muffler is actually pretty good. A 3 db reduction was easy to get just by adding the SuperTrapps but I do not know how horsepower was affected. I do know Frank Catt has done a lot of work on this with a design of his own and maybe he would have something to say here. Here is my data, meager as it is, and with some missing records and a few pictures:
A 1 CAV (PowerFlow SS P/N# GE-265X350C60-20886 dual 2 ½ in and dual 2 ½ out)
B 1 CAV + 2 SuperTrapp (P/N# 444-2503 4 in diameter with 12 plates)
C 1 CAV + 2 SuperTrapp (P/N# 444-2503 4 in diameter with 6 plates)
D 1 CAV + 2 home-made baffles (1 ½ in equilateral triangle x 24 in long)
E 1 SpinTech (P/N # 33310 dual 2 ½ in and dual 2 ½ out)
F 2 FlowMaster (P/N # FLO842553 SS Delta 80 Series each muffler single 2 ½ in and single 2 ½ out)
RPM 1,000 2,000 3,000 4,000
A-----84----84----91----92
B-----81----82----88----91
C-----77----81----85----88
D-----83----81----88----89
E---->86 (cannot find data sheets)
F---->86 (cannot find data sheets)
I hope this helps you get a handle on what is out there and if you find something good, be sure to let us all know.
Bob