Speed,Combat,Scale,Racing > Speed Talk

Fox 35 for Speed.

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Speed Demon:
Hi new here, and new again to CL after many many years Lol. I had some experience with Goodyear back in the 70's. This said.

I have an interest in the Fox 35 speed event. I am assembling equipment to put some planes together and hopefully have some fun.

What I am interested in learning is. What can be done to the old Fox 35 to make the most power from it possible? I am aware of the basics, stuffer back plate, hemi head etc. I am wondering more about port timing changes, piston/sleeve swaps, increasing inlet sizing? Next level mods.

Anyone of someone knowledgeable in this area, or may even offer parts? Thanks

Dave Rigotti:
Polish out the "lip" inside the crankcase inlet transfer.
Get a Bill Hughes hemi head insert. (this alone adds 5MPH)
Super Tiger style needle valve assembly. Turn the OD down to .135" diameter only where it crosses the venturi id.
Mill the bottom of the mounting lugs flat.
Use a FOX brand 35 stunt ABC piston/liner. No timing changes made.
Lap backplate mounting surface flat.
APC 8 x 9 prop
40th or 50th anniversary versions do better.

The above gets to 102MPH.

Dennis Toth:
SD,
Since you are coming back I think the first steps should be to get you CL legs back with a sport plane like the Flite Streak or Ringmaster then move to something faster like a combat wing. Once comfortable the FOX 35 speed ships are basic rat racer style ships, lots of plan here: https://outerzone.co.uk/browse_plans/category/results.asp?Level=2&Cat1=CL&Cat2=Sport can do a search at the bottom of the page.

As for engine mods, the stuffer backplate is popular but you could just us the stock one with a very thin gasket and get a similar benefit of keeping the rod from moving to far back. The button head is also popular as are other aftermarket heads that raise the compression. Changing to a better NVA is also something that is done but you can't make the spraybar to small as you need to run suction only so need to have a stable needle. Some have changed the piston/cylinder there are some aftermarket ABC units avialable from time to time. Since the fuel is provided at the contest (by rules should be 5%N) no exotic fuel. Also, no carbon fiber props, commercially available wood or nylon reinforced (APC's or Master Airscrew). Trimming diameter of the props, thinning blades and repitch is allowed.

Best,    DennisT

Speed Demon:
Thank you both Dave and Dennis. Very helpful, defiantly a good advice to get going.

Dennis I have done some recent flying with a buddies Ringmaster, that's what get me into my current dilemma. Yes I am working on a couple "practice" planes.

Dave luckily, I still have a good 40th anniversary from slow Fox 35 project some 20 years ago.

Speed Demon:
Where can I locate fuel, or something similar to what is required?

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