At Brodak, a club member picked up a Stels .049 for me that was being sold.  That’s the engine on the left. On the right is a Stels .049 from my engine bin. 




I can’t find any instruction sheets for either of them.  The one on the left had a data sheet that says to use 40-60% nitro fuel, a Cox glow head, and a Tornado prop.  No prop diameter/pitch recommendation or glow head type recommendation, though.  I’m assuming the Cox 1702 high compression head (duh…) or a modern substitute adapter.  But for props, I’m not sure what to use.  I’m guessing in the 4.5x4 range?

Mark

Incidentally, I got over 150mph out of the final iteration in that design series, and was beating q500 pylon racers in runwatchabrung races.
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That must have got their knickers in a twist!🤣

What are you going to use it for? Stunt 6-2 apc I would stay away from anything tornado. For 1/2a I use 20% nitro 20% castor.