Optimum Primary Pipe Length — Keep the primary pipes as short as possible. Systems are designed around individual 90° and 45° bends, which are 12″ long. Do not use more than 72″ of pipe on each side. This translates into a maximum of 6 pipes per side. Three horsepower will be lost for each additional 12″ section beyond 72″. These recommendations are based on dyno tests with stock and modified Corvette, Chevy II and Log manifolds.
Unequal Length Primary Pipes are OK — Our dyno tests have concluded that variations in primary length have no adverse effect on power when a collector is used. Primary pipes which are equal in length, or as close as possible, are preferred, but in some applications this is just not possible. So, if your pipes going into the collector are not equal, don’t worry.
Pipe Length for Dual Pipe System — If you are restricted to a dual pipe system, pipes should be 45″ to 55″ in length, equal on each side, and run a balance tube the same diameter as the exhaust pipe.
Secondary Pipe Length — Run a minimum of 12″ of secondary pipe after the collector. Adding more length has little effect on power. In other words, “We’ve run 1 to 6 feet of secondary pipe and noticed absolutely no power difference.”