1-5/8" or 1-3/4" headers?

[BADASS03SVT]

i looked at some previous posts but most of them branch off into other subjects. some say headers do nothing, some say there great. i want to do them while my k-member is off. only question is what size? for referance, by years end i plan on having a 6 or 8lb lower with interchangable upper and all other bolt ons. also what size exhaust? 3" or 2.5"? thanks

 

[hj16]

1-5/8" primaries, 2.5" collector

No need to go bigger unless you are pushing 800 at the wheels.

 

[BADASS03SVT]

why not? not saying i dont believe it, just looking for some quotes to back that up. on my last "hot rod", a 1999 dakota r/t pickup with the 5.9L 360. we had mid length headers, that EVERYONE USED AND PRAISED, that were like 1-3/8". this is for 225-275rwhp N/A motors. also most were using single 3" or duel 2.5" exhausts. a new exhaust combo came out...1-5/8" primaries into 3" collecotrs and duel 3" exhaust. sounds like a lot for a 325hp n/a motor huh. well people tried it and actually gained about 15rwhp and 10rwtq on average. the powerband was also braodened. its just sometimes BIGGER ends up being BETTER..

 

[hj16]

All I know is that a 700rwhp KB car on MF runs that size header, works great, and picked up a shitload of power.

And I run the same size header, also works great.

 

[BADASS03SVT]

but would u or he have gotten any more form the 1-3/4"? who klnows. osmeone has to have a set though. i would say there is more power ot be made, especially when tossing 16#s of boost through the motor..it needs to get out too. im no expert...just want some good thoughts and opinions. so u gained from yours? any dyno before/after?

 

[hj16]

Originally posted by BADASS03SVT
but would u or he have gotten any more form the 1-3/4"? who klnows.

These cars dont act like most cars when it comes to headers. They actually need a certain amount of backpressure for optimal results. If you use too big of headers you will lose tons of TQ, and have to go to crazy bost levels to get it back (25+psi)

When I used to have my NA 02GT there were people with only 240rwhp who were using 1-3/4 and getting great results, but these cars dont react like NA cars.

 

[OATS]

You could compromise. Kooks makes a step header that starts as a 1-5/8 primary and jumps to 1-3/4. It uses a 2-1/2 collector. The step principle has been around a long time to promote better low end torque. Kooks sells these direct at a better price (or used to) than JDM sells the the 1-5/8 Kooks for now.

 

[JSHTROD]

Several guys have gone larger than 1 and 5/8's on LT's. With poor results. Do a search here and you'll see some results.