Header Builders

[Signman]

Originally Posted by Frank Castros

What makes ACP, Kromer Kraft and Precision Welding headers special.

Each have their own formulas for tube diameter, length to each step, Step change in diameter, collector size. Overall design of header 4 into 1 or Tri-Y. These factors will determine how hard they suck exhaust out the port, control reversion pulses not allow them to make it back to the valve stalling flow. Controlling signal getting back to the carb effecting fueling. Build quality placing bends and their radius.

Not saying a custom set will "always" outperform a set of box headers.
Depends on the combination.
A box header can be optimal.
Improvement can be minimal.

Improvement can also be impressive.

There are old threads on Speed Talk with comments by Calvin Elston and others which if your interested in understanding theory behind header design are very informative. Search "Exhausted".