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Post  Scotland421 Tue Sep 14, 2021 6:16 pm

I know this is an unorthodox question...Has anyone been able tae install ae muffler tae a Fox Combat Special? It hasnae design fae ae muffler.
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Post  Ken Cook Tue Sep 14, 2021 7:55 pm

There are dozens of Fox Combat Specials. Knowing what you have or posting a picture is a huge help. I practically own all of them with the exception of one or two. Some can be muffled with so so results and only one actually came with muffler provisions which was the Fox .36 MK.5. Essentially muffling these can do harm if not careful. Fox engines have eggshell cases and getting the heat out is important. Certain strap mufflers on the older style Black Head Combat Specials and the Rockets can distort the case if tightened. Depending on muffler design, it's imperative to have a large outlet which doesn't assist the mufflers primary goal of muffling.
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Post  Scotland421 Tue Sep 14, 2021 8:34 pm

It's the MK 3, I'm thinking ae tryin' ae Tatone peacepipe.
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Post  Cribbs74 Tue Sep 14, 2021 10:32 pm

Oh man, now you’ve gone and done it. Laughing

I’ll let Ken get into the particulars, but in short a Peacepipe on a fire breathing Fox combat is a bad idea.

Is a muffler required where you fly?
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Post  Ken Cook Wed Sep 15, 2021 4:49 am

I've used a Peacepipe on other engines with not so favorable results. This was with mildly timed sport engines. The internal chamber and the outlet is considerably small. The MK III really doesn't want to run slow even with the venturi insert. I would feel that the Peacepipe would essentially hold back too much offering a extended lean run which would really be overheating. One other problem with the MK III is the stock head button design. The head chamber is totally flat with the hole for the plug only. What happens with this is that it tends to really force a lot of pressure directly into the plug area which takes the plug out in short order. Unless your engine has adequate head shims or someone has already changed the head design, if you combine the already known problem with a lean overly hot run, I can see this engine eating plugs on a regular frequency. One can only try and hope for the best.
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Post  Scotland421 Wed Sep 15, 2021 8:13 am

Giggle....I stirred up ae hornet's nest....Here is the plan, I'm gaunnie turn a double bubble in the heid button (like K&B did on the DF engines) I'm also gaunnie raise the heid clearance tae .019. And I'm usin FAI fuel wi 25% sig castor. I cannae change the crank timing well, (I'm auld and shaky hands) Wish m' luck?
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Post  Scotland421 Wed Sep 22, 2021 12:19 pm

I ran the engine today wi the suction insert. What ae pussycat. I love this engine! it works on zero nitro well. I'm no gaunnie modify it. No need.


Last edited by Scotland421 on Wed Sep 22, 2021 7:31 pm; edited 1 time in total
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Post  Yabby Wed Sep 22, 2021 4:46 pm

@Cribbs74 wrote:
Is a muffler required where you fly?

A muffler doesnt have to be as restrictive as might be thought. As long as it is seen to be on the engine. "nah, its not that noisy, see ive even put a muffler on it" Lol. Wont defeat the noise meter types, but the odd person in the local park it can work with. lol!

I shouldnt talk, I do have to muffle my engines properly in the local parks to stop exactly that above.

Good luck with your flight! cheers Airplane I love that you have your engines running on FAI fuel. Its on my list of things to try with my own engines. even though its said they wont run or run very poorly (Cox 049) I want to give it a bit of a go.

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Post  Scotland421 Wed Sep 22, 2021 4:53 pm

Hiya Yabby, I use zero nitro on all my engines even Cox. The Cox ones , I use one heid shim and get 17K on ae 5X3
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