Exhaust Header Size
During the exhaust stroke, a good way for an engine to lose power is through back pressure. The exhaust valve opens at the beginning of the exhaust stroke, and then the piston pushes the exhaust gases out of the cylinder. If there is any amount of resistance that the piston has to push against to force the exhaust gases out, power is wasted.
The idea behind an exhaust header is to eliminate the manifold's back pressure. Instead of a common manifold that all of the cylinders share, each cylinder gets its own exhaust pipe. These pipes come together in a larger pipe called the collector. The individual pipes are cut and bent so that each one is the same length as the others. By making them the same length, it guarantees that each cylinder's exhaust gases arrive in the collector spaced out equally so there is no back pressure generated by the cylinders sharing the collector.
What tube size do I need and is bigger
better?
Header primary tube sizes vary on many factors: engine combination, transmission
type, gear ratio and intended use of the vehicle. For example a truck header
will be designed using longer length and smaller diameter primary tubes to
enhance low to mid-range performance, where a header for a Pro Stock race car
will have larger primary tubes and large collectors for the highest flow
available.
Bigger generally is not better when it comes to street driven cars. when you put too large of a header or exhaust on a street driven vehicle, you usually notice a severe drop in low to mid-range performance due to a lack of backpressure.
Consult a quality Header company like
Hedman Headers: www.hedman.com
Hooker Headers: http://www.holley.com/hookerheaders/
JBA Headers www.jbaheaders.com
These are just a few names available.
1-800-704-5385