Originally Posted by David Vizard

Cross Overs and Balance Pipes

The object of the entire muffler tech so far discussed is to end up with an acceptably quiet system; otherwise the point of the exercise is lost.

By using no more muffler flow than needed we are giving whatever mufflers are selected the best chance of doing the job. Unfortunately, mufflers can be a little inconsistent and unpredictable in terms of noise suppression from one engine type to another. Situations involving high compression ratios and long-period cams are usually more demanding in terms of noise reduction. Big cubic inches, shorter cams, and lower compression ratios are easier to muffle. The biggest problem in this area is knowing whether or not a possible combination is quiet enough. If you hit the Dynomax web sight you can hear chassis dyno tests of a wide variety of mufflers (including stock) on an extensive range of vehicles.

Be aware that how the system is installed can also affect the sound level, especially in the vehicle's interior. Do not have the tail pipe ending under the car, as the bodywork will act as a sound box in much the same way as a guitar body. Either have them go all the way to the rear, with down turned exit pipes angled slightly in towards each other, or have side exits aimed 45 degrees to the ground.

As far as power is concerned, tail pipe length after the mufflers has no measurable effect on the power if a large change in cross section is present up stream (toward the motor) of the tail pipe. An open-type muffler, or a resonator box, provides this cross-sectional change. The tail pipe length exiting most glass pack installations is also of little consequence if a resonator box is used, but is of significant influence if not.

Virtually all V-8 exhaust systems can be refined by the addition of a balance or X-pipe. These have two potential attributes: increased power and reduced noise. Extensive dyno testing on both of these factors has indicated balance and X-pipes are 100 percent successful at reducing noise. The reductions amount to a minimum of 1 dB to a maximum of 3 dB with 2 dB being common. As far as power is concerned, things are a little less certain. With engines between about 325 to 550 hp, experience indicates that in about 60 percent of the cases (mostly with balance pipes), the engine can deliver as much as 12 additional hp, with 5-8 being the most common. The other remaining 40 percent tested showed virtually no change in output either up or down. Based on such results, we can conclude that a balance or X-pipe is always a positive asset and never a negative.


Balance pipe sizing seems not to be overly critical. The only really influential dimension is the pipe diameter. This needs to have an area at least equal to that of a 2.25-inch diameter pipe (4 square inches) with 2.5 to 2.75 inches being preferable. Though limited to tests on engines up to a little fewer than 600 hp, there seems to be no measurable benefits to using a crossover pipe bigger than 2.75 inches in diameter. As for the crossover length, dyno results indicate that 18 inches responds in virtually the same manner as 72 inches long.