Adding a Muffler? - RCCanada - Canada Radio Controlled Hobby Forum
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Old 01-15-2008, 08:28 AM   #1
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Adding a Muffler?

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OK Guys here’s the situation;
I have just inherited a 1970 vintage engine that originally had an exhaust baffle tied to the carburetor. (K&B 15)

The baffle has been lost with the years and the Carb has been replaced.

That having been said; the other night I was able to fire the engine up with minor difficulties – it ran up quite well. However, without a baffle or a muffler for back pressure the engine would not tune up and speed control was ‘limited’.

Has anyone had any experience adapting a muffler to one of these ‘Older’ engines?
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Old 01-15-2008, 09:46 AM   #2
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Any of the jobber strap on mufflers will work fine. Engines back then didn't use pressure as they ran smaller carbs and had better suction, although pressure wouldn't hurt it at all. The muffler back pressure will make it idle better too.
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Old 01-15-2008, 11:19 AM   #3
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I have had good results from this company and they are canadian to boot...
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Old 01-15-2008, 11:07 PM   #4
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Hi bbbair,

Was the exhaust baffle a 'butterfly' type screwed over the exhaust?

Or a 'rotary' type that went fore/aft through the exhaust?

If the latter, the two holes need aluminum plugs to seal them. They get held in by the muffler strap. (JB-Weld won't work)

I have a pair of early 70s Veco .19s rigged this way and run great with old O.S. strap on mufflers.

I believe the K&B .15 was used in the 1/4 Midget Pylon Racing class and was a 'revver' rather than a 'chugger'. The baffle was needed because there was an 'idle' rule.(hold an idle low enough the plane would not roll fwd on the ground)

I'm sure there is a Bisson muffler that will work. I'd go with a shorter 1/4in.ID outlet to let the engine 'breathe'

Try a MA 8-3/7-4 and/or APC. Should turn up pretty good.

Don't forget it is NOT an ABC engine. You WILL cook it if it is run too lean.

I think 15% castor/synth with a splash of extra castor would be best. (I think it was optimized for race match supplied 15%, but my memory might be hazy... )

Good Luck. S.M.A.L.L. is cool !

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P.S. The carb bore should be around 1/4 in. If it's too big you'll loose fuel draw.
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