Homemade Performance Mufflers

Mufflers are made to reduce sound, but often at the expense of horsepower. If horsepower isn't your goal but a silent vehicle is then building your own muffler can give you great bragging rights. You can have a homemade muffler without the help of a professional when using glasspacks or baffled mufflers.

Types:

• Glass-packs are mainly used in stock vehicles with a perforated center core surrounded by fiberglass, which absorbs all sound waves regardless of their tone.  More fiberglass packing makes for a quieter muffler, which is one reason why performance glasspacks are so small.  Glasspacks are cheaper and easier to build than baffled mufflers.


• Buffled mufflers use a series of internal metal plates (baffles) to reflect the sound waves back onto themselves, which results in a phenomena called "sound cancellation."  While they tend to flow a bit less that straight-through glasspacks, baffled mufflers often yield a lower and more pleasant exhaust note.

Building a Glasspack:

1. Start with a regular, oval shaped car muffler.  First, cut both ends off of the muffler (where the pipe stubs are) as close to the outer case as possible.  Once you have the ends cut, cut the internal tube to separate the ends. 


2. Cut the pipe stubs off of both ends, and weld a sheet metal plug into the circular holes where they used to be.  Cut a 2.5 to 3 inch hole in the center of both ends. 


3. Measure the length of your muffler case, and cut a length of exhaust tubing (again, 2.5 to 3 inch outside diameter) exactly 6 inches longer then the case.  Measure 4 inches from either end of the tube, and mark a line around its circumference.  Swiss-cheese at the section between those lines with a 1/8 inch drill bit, spacing your holes no more than 1/8 inch apart.

Assembling the Glasspack:

1. Slide your tube into one of the muffler-ends so that the perforated section is just below the end-piece, and weld it in place.  Install that end piece onto the muffler, and then weld that in place.  Tightly pack the entire case with dry, bodywork fiberglass (you can also use stainless steel wool, but it will be louder) available at the auto-parts store.


2. Do not use household "pink" fiberglass; the resins in the pink fiberglass will quickly catch fire while you are welding.


3. Repeat the end-capping procedure on the open end of the muffler, but do not run a continuous weld around the seams.  Instead, spot-weld the pipe onto the muffler end and the end piece onto the case.  Keep the whole assembly as cool as possible to keep from melting or burning the fiberglass.  You can just tack weld the end piece every 3 inches and seal the seams with lead solder or silicone, but it will not look as nice.