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So I just picked up a 78 c121 auto in great shape. Only problem is the previous owner cut a huge hole in the hood for a new muffler when the stock one rotted out. I plan on finding a new hood for it and want to redo the exhaust. I like the idea of a stack but don't want it stinking way up in the air. I also don't want to straight pipe it shorter because I live somewhat in town and I don't think the neighbors would be to happy with the noise. But I found another user that used 2 small engine 3/4 inch mufflers. I really like the idea but im just worried that down sizing the pipe to from 1 inch to 3/4 would be to much back pressure. Anyone have any thoughts? I will upload picture of my tractor and idea I have. 

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:WRS:      There would actually be less back-pressure with two 3/4" mufflers than one 1" of the same design. The area of a 3/4" circle is 0.44 sq in. times two is 0.88 Sq in. The area of a 1" circle is 0.79 sq in. I know that the I.D. of pipe is not 3/4" and 1", but the same ratio should apply. The "T" and two 90s will have a little added back pressure so it will be about the same.

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Let us know if it helps, and...:WRS:

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Sorry for the late reply but thanks for the help. I picked up all the peices I needed and put it together over the weekend. Including a bracket to help support the extra weight. I will soon be getting some header wrap for it. Here are some picks. 

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