So I have 4 or 5 of these engines and have sleeved down some venturis to .242 with .156 NV to make them needle better with an 8x4 apc prop on the bench. I am wondering if anyone has used them for stunt engines in the high rpm low pitch type run ? If so what was your setup and what size sq in plane would you run them on. They seem to be happy running 7" props but were not very happy with 8" and 12.5 to 13k rpm as far as needle adjustments went until I made the smaller venturis . Is this a lost cause? I have them already and like them ,but I'm looking for suggestions on setup and plane size
Thanks
Mike Bush

Thanks Mike. One new in box that I have is different from the rest in that the muffler is different with a much smaller outlet and the trust washer is completely different. The stamp in the box is Jan 27 199?, I can't read the last # of the date. Maybe that one is milder than the rest. I'm thinking a plane in the 330 sq in size would be close.
Mike

Mm is that the sterling/Brodak Yak 9. 323 sq in ?  Are you happy with the power on that plane ?
Mike

8-4 apc is gonn'a load that engine badly. Mine has a 7-4 apc and pulls a lightened Yak-9 trainer with stationary flaps pretty good.

MM

   That sounds disturbingly weak for stunt, I would have expected it to be pretty strong. f it won't even spin 8-4, then it is far too weak, the 15FP has no problem at all with a 9-4  and pulls airplanes like the Yak around with reasonable authority. I think Paul Walker test-ran his 15s in a Mike Deitrich Cobra.

   That was one of the engines we did not try in the small engine experiments, for more-or-less the same reason from the other thread - I could never find one that didn't require some mechanical fixes or required extensive break-in.

     Brett

   That sounds disturbingly weak for stunt, I would have expected it to be pretty strong. f it won't even spin 8-4, then it is far too weak, the 15FP has no problem at all with a 9-4  and pulls airplanes like the Yak around with reasonable authority. I think Paul Walker test-ran his 15s in a Mike Deitrich Cobra.

   That was one of the engines we did not try in the small engine experiments, for more-or-less the same reason from the other thread - I could never find one that didn't require some mechanical fixes or required extensive break-in.

     Brett

That would be a Steve Wooley Cobra, monokoted, something like 34 oz. I'm not real familiar with Deitrich's Cobra, but think it was larger with a bubble canopy vs. razorback arrangement. The Wooley Cobra is HUGE for the original Fox .35 stunt. Over 600 sq. in., IIRC.    Steve

PS: I'd think an ARF Flite Streak would be a fair test bed for a Fox .15bb.

Hello

I would make a twin using a pair of late model Fox 15's which should be happy with an 8x4 or a 7.5x4
If you want power they need to spin up eg F2D combat engines normally use a 6.5x3.5 or 6.5 x3.75 prop to get useful power an an early Fox 15 BB with a high compression head would not like an 8x4 holding it back but the latter sports timed engines used much lower compression head buttons (there were 3 types)

Regards Gerald