I'm running Langdon's cast headers on my '66 Elco/250. In the box with the headers was instuctions as to what type of glasspac[perforated core], length [36"], size tail pipes[2"].
I took the Elco to the exhaust shop with the instructions and left it. When I went to pick it up, it was LOUD. I looked under it and asked "what the length on the mufflers?" Reply: "we didn't have any 36" so we installed 30". We had a discussion about "verbal contracts" and they agreed to order a pair of 36" perforated core glasspac.
The difference was night and day. It's prety mild with no intrusion at cruise, nore do people stare at it when I drive by.
