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Engine basics => Engine set up tips => Topic started by: Christopher Root on July 26, 2021, 08:40:49 AM

Title: Fox .36X BB
Post by: Christopher Root on July 26, 2021, 08:40:49 AM
Hello! I recently inherited what looks to me like a Stirling P-51 Mustang with a Fox .36 X BB engine on the front. Test ran it yesterday with 10% nitro 29% oil (50/50 mix).  Seems like it breaks into a two-stroke cycle around 10,600? 10x6 prop.  Seems high to me . . ..
Title: Re: Fox .36X BB
Post by: Dan McEntee on July 26, 2021, 09:14:13 AM
  That's a combat engine. A good engine for the Sterling Mustang is the LA.25. Think about the difference between the two??!! You may want to find a combat guy that would pay a good price for that engine and buy yourself a more stunt friendly engine for the P-51.Lots of possibilities there.
  Type at you later,
  Dan McEntee
Title: Re: Fox .36X BB
Post by: Christopher Root on July 26, 2021, 09:19:18 AM
Does it share the same mounting pattern as the Fox .35? If so, I've got a few that I can swap into place ..
Title: Re: Fox .36X BB
Post by: Christopher Root on July 27, 2021, 05:55:03 AM
So I checked last night, and no, the Fox 35 and Fox 36X do not share mounting holes. The 36X seems to be quite a bit beefier all around.  Can it run on 0% nitro?
Title: Re: Fox .36X BB
Post by: Dan McEntee on July 27, 2021, 08:12:22 PM
  I imagine that it can run on 0% nitro fuel, but why? That is a lot of engine for that airplane. It's an engine designed to fly a combat model in excess of 100mph and it will take a lot work and testing to "detune" it to fly a model that could be flown the way it was designed for with a Veco .19. If you know how to do that, then fine, but I figure you wouldn't be asking the question if you did. Keep your eyes pealed  for an LA.25 or rework the engine mounts for your Fox .35. It will be much easier to get get set up and flying consistently.
  Type at you later,
   Dan McEntee
Title: Re: Fox .36X BB
Post by: Christopher Root on July 28, 2021, 06:58:44 AM
Thanks! I tried 0% nitro last night--didn't work so well. I was able to dial it in a little better with my 10% nitro, and felt like I could get a good idle with that.  What did you say was a simple way to de-tune it?  Head gaskets? I'd hate to start playing around with changing the engine mounts. .

C R
Title: Re: Fox .36X BB
Post by: Peter in Fairfax, VA on July 28, 2021, 11:19:55 AM
Yes, Dan is right that a 36x on pressure will go 100 MPH.  However, on suction, with the insert installed, maybe 85 MPH.  And that's on a combat model that is designed for speed, maybe 350 square inches.

Just last week, a member of our club brought a larger plane, a Sig Banshee, with a stock 36x on suction.  Took us a few minutes to get the tank sorted out, unrelated to it being a 36x, but then it ran great.  No where near 100 MPH for the 510 square inch stunter.