Help??

Looks like a muffler without the front cap and tie bolt installed.

Look down inside and you'll probably see holes along the tube. It is a venturi style muffler that was popular when we first started using mufflers. Mac's used to sell them as did several other after market manufacturers. They didn't reduce the power very much, but they were loud. As the manufacturers learned more about mufflers, the closed and quieter muffler that came with the engines became universal.

also known as a "flow through" muffler. Want another??

AJC

Do you think in a stock class of racing were ground tach rpms were checked AND every used the same propeller, that this type of exhaust would increase airborne rpms over a stock closed expansion style?