Somewhere (I can't find the thread now) Larry Renger (IIRC) recommended drilling out the Cox production engine's venturi, which narrows down beyond the NVA, to the existing exterior diameter. I tried it with one of mine, and it sounds more like a Black Widow than a Babe Bee! And still starts,  draws fuel, and needles just fine.  So my thanks to Larry, and you guys oughtta try it if you want to make your Surestarts into superior sport engines.

No official tach comparisons, sorry.  But a significant upgrade according to my ear.

On a plane but on the ground, Ray.  But I did point the nose up, down and all around!  The mod doesn't seem to have affected the fuel draw at all. 

Right, extra power has to come from somewhere--no free lunch, huh.  So who notices an increase from 1/2 oz. to 3/4? I expect I'll do all my surestarts this way (I have 8 I guess, hard to keep track--4 on planes and 4 still wrapped up in the coffee can. I think.).

P.S. Ray, I did fly the little beastie and it did fine, loops, eights, inverted.