11-09-2017, 01:40 AM
Two comments for other DIY fans.... for Mac engines with just about any shape expansion chamber you need to end up with the length of the header in the range of 9 to 10" from the face of the piston to the small end of the scavenge cone. The system shown here is a neat idea but at least two inches too long in the shortest configuration to perform well. It would be virtually impossible to build a slip joint system such as the one shown that can place the chamber in the correct relationship to the engine.
Another consideration... Mac engines have fragile exhaust header mounting locations thus the use of flex between the header and pipe is highly recommended in order to provide compliance between the pipe and the header as the kart flexes and the motor shakes around. A rigid assembly such as the one shown here looks nice in the shows but it will end up tearing the inserts our of the two exhaust port screw locations if used on a runner, especially on bumpy tracks and on karts with swing mounts that are rubber mounted at the front end of the mount.
In summary....very nice fabrication of a system that looks great but is not engineered to run fast or long on the track.
Steve O'Hara
Another consideration... Mac engines have fragile exhaust header mounting locations thus the use of flex between the header and pipe is highly recommended in order to provide compliance between the pipe and the header as the kart flexes and the motor shakes around. A rigid assembly such as the one shown here looks nice in the shows but it will end up tearing the inserts our of the two exhaust port screw locations if used on a runner, especially on bumpy tracks and on karts with swing mounts that are rubber mounted at the front end of the mount.
In summary....very nice fabrication of a system that looks great but is not engineered to run fast or long on the track.
Steve O'Hara