carb air boxes

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dlrude
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carb air boxes

Post by dlrude » Tue Feb 24, 2015 09:45

Hello,

I am repairing a 7ccm with a c90-12f and using the drawings to put it back together. The engine installation drawing calls out a different carb airbox number depending on which fuel system that you have and which carb.

This plane has a 26 gallon fuel system and a Stromberg carb so it calls for a 4-877-3 air box.

Looking at drawing 4-877 rev. G I just can't see any mention of a -3 mod or part.

Does anyone know what the -3 implies? What is a -3 box compared to others?

Thanks, Dave

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David Johnson
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Location: Jasper, Georgia
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Re: carb air boxes

Post by David Johnson » Fri Feb 27, 2015 16:18

Dave, everything I have seen uses the 4-601 air scoop assembly. I don't have the 4-877 print to look at. Every Champ I have ever seen has this air box. Except for the L-16 with fuel injection. David J./Jasper, GA

brink
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Re: carb air boxes

Post by brink » Fri Nov 16, 2018 18:15

This post is three years old, and I hope you got it resolved, the basic Champ Air Box and Airmaze filter assembly was unique to our 7AC Champs. Personally I’ve seen several air-boxes that were installed but not supported by a 337 or other paper work or up dates service bullitens or the like. Univair wants over $600.00 for an Aeronca air box wag Aero is a little cheaper. But wag Aero also offer all the parts to build up an air box, cost about $700 if you count the piece.by piece with shipping. Wagner sold out to Wag-Aero, and wag Aero kept the parts for the air box in their parts listing, even tho some parts will back order when requested. The Cessna 150, 0-200 airbox fits our Champ, But it’s not legal. And it’s design will not support the heat required off the stock exhaust system in the straight pipe configuration, personally I like the two part design,of the Aeronca air box, easy to clean,easy to repair, and compared to the Cessna 150 version much larger, also the aluminum duct is required not scat or sheet tubing, even tho it’s not call ed out in the Type Certificate. You should get at least a 25 RPM to 50 RPM drop when carb heat is applied, in cold up north country I flew out Of Laurel airport, the mechanic had cut and rapped fire shield from the right baffle and rapped it around the aluminum tubing going to the carb air box to get the proper drop in RPM during the winter months in Maryland.

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