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Wheeler Piston Scallop Mod (WS Mod)


Here is a 2-stroke modification to increase the blow-down time and increase the exhaust pulse signal strength to the pipe. This modification is not for beginners and can be done by hand, machine, or CNC. The summary of the mod is to modify your piston dome to match the shape of the upper portion of the exhaust port (the curve of the oval). This allows more area to open for the exhaust to exit in a shorter time (degrees). One method would be to blue the exhaust side of the piston, insert it into the cylinder up to the point of the exhaust closing, and mark the piston with a dental tool (sharp narrow tool). Next mark on the piston the outer edges of the exhaust port (some thought when modifying triple exhaust ports). Finally decide on the limits of upper land on the piston, the angle of the cuts, and edge cut radiuses. Carefully cut the piston(s) with appropriate tooling. Here are some example pics of how to modify a Blaster engine. Many other layout and/or machining approaches are, of course, possible for this modification, and exhaust port timing as well as time/area need to be considered.

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