ffkiwi

I've had an absolutely standard TD 049 up to just over 25,000 on 30% nitro on a DC 5-1/4 x 3-1/2 prop [which are anything but what they're supposed to be, pitch wise] which are very flexible-I'd imagine the blades had washed out to very little actual pitch. It sounded fantastic-and had heads turning-but it didn't fly the model [1/2A Witch Hawk] worth a knob of proverbial on that prop-and I went back to a Cox 5x3 black. Always remember-THRUST is what flies models, not revs..........

....as for modding-well the sky is the limit I suppose-once upon a time people even used to get their own cylinder blanks from Cox and do their own (usually schneurle) bespoke cylinder porting, but that avenue has dried up. As CP has said-dozens of articles have been published over the years on hotting up Cox engines. Some of it requires access to precision machine tools, some can be done with simple tools. Blueprinting, using cylinder shims, and playing around with head clearance and alternative heads are the start points, as well as opening up shaft timing and the carb bore, plus improving balance, lightening the piston and flow contouring. Done well, a lot of gain is possible-done ineptly, you now have an interesting paperweight for your desk..................
ChrisM
'ffkiwi'