RE: 'Wild Thing' Construction Pictures
Ross, I believe I mentioned this to you in the past. YOUR TUNED PIPE CONNECTION IS MUCH TO LONG!! You can't just stick a pipe anywhere in the exhaust circuit and get any added performance from it. It has to be tuned to the exhaust/intake cycle and for best performance, the engine should be timed for a pipe. A tuned pipe works by creating a reverse pressure wave back to the engine at the precise time that the incoming fuel charge starts to exit the exhaust port (on a pipe timed engine, the exhaust remains open for a short period after the intake closes). The returning pressure wave from the pipe pushes the fresh fuel charge back into the combustion chamber thereby "super charging the engine". As MCH01 indicated, each engine, depending on the way the exhaust and intake ports are timed, has a specific ideal exhaust length to the wide part of the pipe. It will also vary depending on the volume and style of the pipe. On my MAC .21 I run a MAC Products .21 unmuffled pipe at 9 1/4" (about 235 MM), cylinder center line to the pipe wide point. Believe me, the engine is very happy!
I put the large tank in my boat on the side because it's closest to the CG and being the heaviest tank in the boat, has the greatest affect on CG as the fuel is consumed. That places the hopper tank as close to the carb as possible giving me uniform fuel flow. The impact on tracking due to the larger tank on the side is negligable and is controlled by the trim tabs. AS far as CG location, it's where John Finch recommends in his build instructions. Exact distance from the transom is a government secret. Actually I'm at work and the boat is not with me today so I can't get you a measurement right now.