CorvetteForum - Chevrolet Corvette Forum Discussion

I modified my stock LT1 mufflers. I wanted some more power and sound before purchasing a hi-perf system.

The modification was successful. The car sounds slightly louder at idle and moderately louder at WOT. I am sure the back pressure is significantly reduced. I wonder if what I discovered was the "sound cancellation" principle advertised by the number one brand performance exhaust system.

The modification consisted of removing the first 1 3/4" length of inlet-side muffler tube inside the main muffler body. (just on the inside of the exterior vertical end surface of the muffler body's inlet side). I chose to remove the pipe in this location because the first solid sound baffle is located 1 3/4" in from the inlet end of the muffler. This baffle extends across the entire area of the main muffler body and does not have any perforation holes in it. By cutting the inlet pipe within this first baffle region, the exhaust coming into the muffler has a direct low-resistance short-cut to the center tube in the muffler, which is the exit tube to which the tips are connected.

I accessed the pipe by removing a 2" by 6" section of the muffler skin.

The only tools I needed to cut the muffler parts were: sabre saw, drill, Dremel.

After I cut the inside pipe as described above, (1 pipe on each muffler) I covered the 2" x 6" hole I had made in the muffler body with 2 layers of 26 gage galavanized sheet metal, that were separated by a 1/8" thick layer of fiberglass insulation. I made the sheet metal patches slighly larger than the size of the hole that I made in the muffler body, for a better seal. I fastened the sheet metal to the muffler can using self tapping hex head sheet metal screws.

If you do not cover the opening in the muffler body, the sound is much louder, and you get a little bit of crackling when the motor is winding down.
You can experiment with the sound you want by varying the size and location of holes. (Make sure the exhaust gases have a clear path to travel away from the vehicle without contacting the vehicle.)

I am contemplating the next stage of this modification: which is to enlarge or add to the number of holes in the first pipe beond the cut I made. This is the first perforated baffle region of the muffler. This may increase the the sound additionally.

This modification is a low risk mod (money-wise) if you are waiting to install new muffs and discard the stock ones anyway.

I am interested to hear comments from people who have donw this andpeople who are planning to do it.