Quick header question.....
Melting Slicks
Joined: Dec 2003
Posts: 2,857
Likes: 2
From: pawleys island sc
Burning Brakes
Joined: Jan 2002
Posts: 885
Likes: 0
From: The Woodlands Texas
Likewise, when you install 1-3/4" headers and then modify your car to a higher than originally planned level 
you will find the 1-3/4" primaries will choke the engine back and then you have to replace them with 1-7/8" primaries - like Kooks
The whole thing comes down to a very technical amount of stuff
related to ehaust pulses scavenging the cylinders, vacuum pull, back pressure, etc etc. Basically, anything less than 400hp go with the 1-3/4" primaries and anything over 400hp go with the 1-7/8" primaries. The 1-3/4" headers on a stock engine will add about 25-30RWHP and about 30-35 lbft of torque depending on the manufacturer design when combined with an aftermarket exhaust and a dyno tune.
Good luck.
you will find the 1-3/4" primaries will choke the engine back and then you have to replace them with 1-7/8" primaries - like Kooks The whole thing comes down to a very technical amount of stuff
related to ehaust pulses scavenging the cylinders, vacuum pull, back pressure, etc etc. Basically, anything less than 400hp go with the 1-3/4" primaries and anything over 400hp go with the 1-7/8" primaries. The 1-3/4" headers on a stock engine will add about 25-30RWHP and about 30-35 lbft of torque depending on the manufacturer design when combined with an aftermarket exhaust and a dyno tune.Good luck.
