I have been trying to figure out why my Stunt Supreme won't run worth anything. It's doubly strange because it was done by GMA. I set it on the bench beside a good Combat Special and examined them in detail. What I found was strange. The piston in the SS goes a lot farther down than the CS. You can see the bypass ports in the SS, but not the CS. The SS has no sub piston induction, the CS does. The stroke on the SS is less than the CS. If all else was equal, the SS piston should be higher than the CS at BDC. The only thing I can think of is that somewhere along the line, someone installed a 29 rod in the SS. This assumes that the 29 rod is shorter than the SS. If it wasn't for having to hand make new gaskets, I would simply tear down the CS and the SS and compare them. Does anyone out there know if the rod on the 29 is shorter than the Stunt Supreme? The P/N is different.