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  #1  
Old 07-03-2010, 07:40 PM
BigJohn BigJohn is offline
 
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Location: Gloversville, NY
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Default Muffler positioning - cowl opening for exhaust pipe

A question for those past this point. How much and which way did you have to trim the lower cowling opening for the exhaust pipe? It looks to me like the muffler and the four pipes from the cylinders are a tight fit with other parts and the cooling shroud. In order to move the muffler to the right to clear the cooling shroud on the left it seems that the hole in the lower cowl would have to be enlarged considerably. I'd like to know how earlier builders handled this before I start hacking out a bigger opening!
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  #2  
Old 07-03-2010, 11:23 PM
rvbuilder2002 rvbuilder2002 is offline
 
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The muffler is designed to fit with it exactly centered under the bottom of the engine.
This will give enough clearance for the cooling shroud and should put the exhaust pipe near the center of the cowl cut out.
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  #3  
Old 07-04-2010, 05:22 AM
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Geico266 Geico266 is offline
 
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I did need to go past the scribe lines on the exhaust hole in the bottom cowl as needed to allow for 1/2" clearance. I also trimmed several inches off the end of the exhaust pipeon the muffler though.
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Last edited by Geico266 : 07-07-2010 at 06:52 AM.
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  #4  
Old 07-04-2010, 07:01 AM
BigJohn BigJohn is offline
 
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Scott, - when I position the muffler exactly centered the tail pipe rests against the side of the hole in the cowl. If I end up with the muffler centered I will have to cut the opening bigger to get the 1/2 inch clearance.

Larry - When you cut the pipe, did you square it off, or slant it, and if so which way.

Both - Thanks for taking time out of your holiday weekend to watch the forum! Have a great day.

John
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  #5  
Old 07-04-2010, 07:09 AM
JBPILOT JBPILOT is offline
 
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Default BigJohn

Leave the pipes a little loose. Put on the lower cowl, and move the muffler until it is centered in the scribed hole. Tighten it up best you can, then take the lower cowl off if needed, and tighten the pipes more if needed. You should not have to over-size the hole.

John Bender
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  #6  
Old 07-04-2010, 07:27 AM
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Geico266 Geico266 is offline
 
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Quote:
Originally Posted by BigJohn View Post
Larry - When you cut the pipe, did you square it off, or slant it, and if so which way.
I slanted it with the opening aft. I don't think it makes much difference, but it looks better, IMHO.
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  #7  
Old 07-04-2010, 09:02 AM
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Tony_T Tony_T is offline
 
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Default Muffler fit...

There is a depression in the cooling duct where the #2 exhaust spring needs to be centered if it is to clear the duct, at least on my installation noted by red arrow:


another look:


On mine, this resulted in the exhaust pipe almost touching the outboard side of the pipe opening in the cowl and I trimmed the opening about 1/4" bigger to give it clearance.

Tony
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  #8  
Old 07-05-2010, 06:44 AM
BigJohn BigJohn is offline
 
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Yesterday I precisely positioned the muffler in the center of the engine by using a plumb-bob. Snugged the mounting nuts and reinstalled lower cowl. Same result, exhaust pipe up against the outside of the cowl opening. See photo at: http://www.mykitlog.com/users/displa...g=107782&row=1

Scott, I believe you that the design of this is that when the muffler is centered so will the exhaust pipe be centered in the hole. But it just doesn't work out that way with my combination of parts. Maybe my muffler pipe is "off" a bit, or my cowl is a little different. Keep in mind, this is the cowl that I had to trim back about a 1/4" on the left rear to get the front to line up with the spinner.

So here is what I am going to do:

1. Proceed with installing the cooling shroud inside the cowl.
2. Test install the cowl and reposition the muffler to center the pipe in the existing hole.
3. Check to see if I still have enough clearance for the pipe and springs on the left side.
4. If all clearances look good I torque the mounting nuts and be done.
5. If not enough clearance on left side enlarge the cowl opening and position the muffler for best clearances all around.

I'll let you know how this goes in a few days. Once again, thanks for all the advice. I thnk if I ever get this airplane done I will have to add a plaque giving credit to all the VAF members!

John
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  #9  
Old 07-05-2010, 08:17 AM
Mich48041 Mich48041 is offline
 
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Default muffler fit

Big John,
My muffler fit exactly like yours with the tail pipe touching the right side of the cowl opening. So I enlarged the hole. I figured that nobody is going to look under the cowl to see how it looks. If anyone thinks that the enlarged hole will create a problem with cooling or drag, let me know and I can patch the left side of the cowl opening to make it smaller.
Joe
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  #10  
Old 07-05-2010, 09:09 AM
BigJohn BigJohn is offline
 
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Hi Joe, good to hear from you on this. And good to know I am not alone with this issue. Tony T. reports he had to enlarge his opening as well. I'd be curious to get Scott's take on this, as apparently all mufflers or cowls are not created equal. Actually, I am suspecting that there is just not enough bend in some of the muffer pipes. I can see that if the pipe was bent inward just a tad more, it would line up perfectly. I don't suppose there is any way to bend it (stainless) in the field. John
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