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Message:: [QUOTE="Dr. Jeff Harper, post: 539056, member: 22311"]More Progress: A little BLING doesn't make a race car any faster . . . you just like looking at it more (if that is possible!).  My Familia is now at the header shop having a set of stepped headers made with merge collectors. The primary tubes will be [are suppose to be] equal length (and somewhat short), with the first 50% of the  length at 1 5/8", and the second 50% of the length 'stepped up' to 1 3/4", then into the merge collectors.  This is current header theory for drag cars with open exhaust (no mufflers or tail pipes).  The idea is to keep the speed of the exhaust gasses as fast as possible.  As the gasses meet the step up in size it expands, causing a 'negative pressure wave' to travel back up the pipe toward the cylinder head.  The same thing happens when the exhaust arrives at the merge collector. The combination of these compounded negative pressure waves increases the speed which creates a greater ability to 'evacuate' the combustion chamber which allows more intake charge to enter; therefore, the horsepower. Claims of 20-30 horsepower over traditional headers are common.[/QUOTE]