[SEL] Small Engine Muffler

[Ron Frost, Kersey, PA]

Tell you what I did for a 3.5HP Briggs that I wanted quiet. I started  from the engine with  1/2" pipe as that was the size of the engine connection. Out to a piece of 1-1/2"  about 10" long. Calculate the cross sectional area of the 1/2" pipe and then the area of 1/8" holes. Divide the pipe area by the 1/8" area and this will give you the number of holes that equal the exhaust pipe area. Drill this number of holes into a 5 or 6"  end section of the exhaust pipe. Weld a cap on the end of the exhaust pipe, forcing all the exhaust gas through the small 1/8" holes. Weld a washer to one end of the 1-1/2" pipe with a center hole enlarged to fit the 1/2" pipe. Insert the engine end pipe through the washer just past the holes you drilled and weld it in place. Now put the tail pipe into the muffler housing and pack steel wool around it With an inch or two of the tail pipe inserted into the muffler and after it's packed, slide the second washer down as a cap for the outlet end and weld it to
 both the housing and the tail pipe. The big thing to be sure of is not to restrict areas less than what the engine outlet size is. Too much restriction will cause excessive heat and destroy the engine valves and cylinder. A loss of power will also be noticed. I'd also use elbows and nipples to get the muffler down under the tractor and pointed toward the rear.
For 3/4" pipe and 1/8" holes, you will need about 36 holes to equal the exhaust area. You could also go to 1" tail pipe, say 12" long beond the muffler.  
Have fun. Experment.
I'd like to see some pictures of what you end up with.
Ron


Andy Glines <andyglines at hotmail.com> wrote:
I need to build a muffler for my 6 HP Wisconsin. The goal is to be as quiet 
as is practical. This engine is on my Gard'n Mast'r tractor that I want to 
drive at shows. I want something that I can talk over while its running. 
Exhaust is 3/4" pipe. Who has design tips?

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Ron Frost
Kersey, PA
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