Exhaust systems: defined?

I have a little bit of an off the wall topic,

How much does a header effect the performance of a quad? I know that exhaust systems have better flow and that helps "open up" the quad, especially when the engine has been modified significantly.

The reason I ask is because I took the header and slip on off of my 400 to clean up, and I noticed that my header was the same dimensions as the stock one. I am curious if 1.) Other headers are much larger than the stock one, and 2.) if they are, will this size make a difference in performance?

I appreciate all the help. :D

it makes a difference on size and shape but not nearly as much as it does on 2strokes

So you're saying that there would be a slight performance increase?

Does anyone know how much bigger an aftermarket header is vs the stock header? I have Curtis Sparks and White Brothers full systems before, and neither really stand out as huge in my mind...

MY POWERBOMB IS ALMOST A FULL 1/8TH INCH BIGGER ALL THE WAY DOWN. BUT IT HAS STEPDOWNS FOR THE MOTOR AND FOR THE CAN. SO IT PROLLY DONT MAKE MUCH DIF. THAT IT IS BIGGER.

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Originally posted by bigbad400
MY POWERBOMB IS ALMOST A FULL 1/8TH INCH BIGGER ALL THE WAY DOWN. BUT IT HAS STEPDOWNS FOR THE MOTOR AND FOR THE CAN. SO IT PROLLY DONT MAKE MUCH DIF. THAT IT IS BIGGER.

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I see, do you mean 1/8th of an inch bigger in diameter or circumference?

Someone I know got a power bomb for his Raptor 250, and asked me to help put it on a week or two ago. The header was WAY bigger than my 400ex's header, haha.