I converted the stock muffler today. It was a pain. I ground off the crimp instead of bending it open and brazed halves back together and installed a 1/2 inch EMT conduit for an outlet. It's rough looking but functional. The engine is stock except for the now modified muffler. I got 6800 RPMs. with a 17/8 Xoar prop. Thats an increase of 500 RPMs over the 6300 box stock configuration. I was hoping for more after seeing how much baffling was in the muffler. I'm still a long way from the 7500 to 8000 some are getting. I'm planning to remove the 9.53mm carb and test with a 11mm carb on stock intake to see what will do. I'm not expecting much though maybe 200 RPMs
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