Rinehart exhausts, Vance&Hines exhausts, Samson exhausts, and others

Straight pipes:  Open straight Harley Davidson exhausts perform poorly in the 2500 to 3800 rpm range.  If they are 34" or longer, they do not perform really well at any rpm.  Symptoms include missing, backfiring through the carburetor, reversion (fuel dripping out of the air cleaner) and poor acceleration.

Open mufflers:  "Gutted" mufflers with stock (or stock-like) Harley Davidson exhausts header pipes tend to perform poorly in the same rpm range as straight pipes and exhibit similar symptoms.

Long thin mufflers:  Long, small diameter Harley Davidson exhausts & mufflers with full-length baffles often exhibit the same symptoms as straight pipes, although their over-all performance may be better.

High performance 2-into-1 systems:  2 into 1 systems are often poor performers in the 2000 to 3000 rpm range.  Harley Davidson exhausts of the 2-into-1 type deliver a significant torque dip at 2500 which is slightly less than 60 mph in top gear for most stock Harley Big Twins.

Header pipe diameter:  The great majority of Harley engines, of any displacement, do their best work with 1-3/4" diameter exhaust pipes.  Larger pipes tend to suppress mid-rpm performance and, for that matter, seldom deliver the best power at high rpm either.

Header pipe length:  The stock header pipe is about 30".  Multiple tests, made by several groups, confirm this length as being very nearly the best for all-round performance.  Shorter (less than 27") and longer (over 32") header pipes significantly reduce peak power, throttle response and over-all performance.  An exception to this "rule" are a couple of the high performance 2-into-1 systems which work very well with longer (and un-even) header pipe lengths.  Stock Harley header pipes are near-perfect in diameter and length.

Muffler size:  It is not possible to make a muffler quiet, small and powerful at the same time.  One can choose power and small, quiet and small but not all three.  The reason stock mufflers are poor performers is because they are small and quiet.   However, small and loud is not a guarantee of performance.  In general, small mufflers with large straight-through, perforated tube baffles (looks like a tube with many holes drilled in it) make the most power and the most noise.  An exception to this rule (there may be more) are the popular H-D Screamin' Eagle (and Cycle Shack) small slip-on mufflers which perform very well yet are not straight-through designs.  The popular louvered core baffles restrict flow at full throttle & high rpm and reduce power a bit as a result.

Product Listing : Harley Davidson Exhaust Systems

Back to : Harley Davidson Mechanics Directory Page