Martin, I made the header insert on the final production version pipes a little longer so they would telescope over some folks precut header pipes. Some header pipes are out of round, and don't telescope well. You are able to telescope the pipe over the header pipe, correct? As long as you have a little (~1/8") of the cylindrical section on the ID of the pipe you'll be fine. The cylindrical section is 17/32" long on the CNC inserts, so cutting ~.4" from the header end should be no issue; there is stuill about 0.6" of the insert in the square transition, so it won't come loose. I have one 180* header pipe that is actually cut about 1/8" into the bend. It still telescopes ~1/8" into the pipe, but I also water cool my header pipes to help the couple life (and preheat the head cap water
).
Marty, Are you running the 2008 CMB liner (19.5mm OD) in your MAC?
I can say that 7 3/8" is too short on my MAC21 Seaducer. It would't get on the pipe at all. It was my second prototype pipe that I had reworked from a NR to MAC style and left the header end too short. I have since reworked it and will try it at 8.25" in a couple Saturdays.