1 3/4 or 1 7/8 headers

[Jonny5974]

I'm getting ready to work the exhaust on my car. I've been looking at the kooks and lth brand headers for it. My debate is which will be the best to support what will eventually become nothing more than a full bolt on car. Right now it's the common CAI 2.4 pulley and tune, but the very near future will bring a VMP 67mm throttle body and ported elbow to wrap up everything I want to do on the car for now. And if anyone has any review on the VMP elbow I'd like to know about that too cause if it's not worth the extra 300 than I'm sure it can be spent else where

[sheppd01]

I have heard people say for the 07/09 at least that 1 3/4 is better because the engine needs a little back pressure and 1 7/8 may actually loose a little HP if the engine isn't built. I have no idea if that is true or not. I am also going to be putting headers on my car soon. I am going with 1 7/8, 3 inch collector and H pipe. Bigger is always better in my book.

Edited November 12, 2015 by sheppd01

[mhr1961]

For street use, in general a larger diameter header (primary tube) is not better because you may lose some low to mid range hp/torque. If you are racing at or near wide open throttle then bigger may be better. Here is an interesting article for you that may be of some help

 

http://www.sandersonheaders.com/Lets-Get-Technical.html

[sheppd01]

For street use, in general a larger diameter header (primary tube) is not better because you may lose some low to mid range hp/torque. If you are racing at or near wide open throttle then bigger may be better. Here is an interesting article for you that may be of some help

 

http://www.sandersonheaders.com/Lets-Get-Technical.html

That test was done on a normally aspirated Chevy engine.

 

Try this.

 

http://www.svtperformance.com/forums/showthread.php?940409-Headers-and-Dyno-Tune-this-wekend-any-guesses

 

Either way it doesn't matter to me. Wide open is the only way to drive a Shelby ?

Edited November 12, 2015 by sheppd01

[mhr1961]

That test was done on a normally aspirated Chevy engine.

 

Try this.

 

http://www.svtperformance.com/forums/showthread.php?940409-Headers-and-Dyno-Tune-this-wekend-any-guesses

 

Either way it doesn't matter to me. Wide open is the only way to drive a Shelby

 

You are correct that it was done on a chevy NA engine. It doesn’t matter what brand of engine you are putting headers on nor does it matter whether the car is NA or SC'ed the principals are the same. The key with making headers work is to select a header that keeps exhaust velocity at optimum levels, maximizing the optimal back pressure levels while also providing improved flow. Whether Super Charged or NA too much flow is not always a good thing which goes back to the fact that bigger is not always better. I was just trying to provide the OP some background on header selection in general. The other site you mentioned was a good reference as well, especially for supercharged engines. The bottom line is whether supercharged or NA the first criteria for header selection is to determine what type of driving you will do and that will help you determine what header is best to select. The reality is you can make educated decisions and select what you think is the right header but you never really know exactly what you are going to get from headers until you do a “before” dyno run and then bolt something up and do an “after” dyno run.

 

 

edited for spelling

Edited November 14, 2015 by mhr1961