What size header for my blown 4.6L???

[Gearbanger 101]

Alright, it’s not a Mustang, but it is a 4.6L. Thus far, the plan is….Ported PI heads (single stage) and stock PI cams, forged bottom end with 18cc pistons, 9psi Allen Roots Supercharger with 75mm T/B and 90mm Lightning MAF. Seems as though the only company that makes a really nice header for my car would be Kooks. I plan on getting the ceramic-coated ones, but I’m debating whether or not the 1 5/8 mid length headers will do, or is it necessary to step up to the 1 ¾ headers? As it sits, they’re already gonna cost me a mint, so I don’t want to go with the bigger header if it’s only going to gain me a couple of horsepower. At best, the car might make 370rwph if I overdrive the M-90 a little at a later date, but as it sits, at 9psi it should run me around the 350rwhp mark.

What are your suggestions?

 

[nickthegenius]

Alright, it’s not a Mustang, but it is a 4.6L. Thus far, the plan is….Ported PI heads (single stage) and stock PI cams, forged bottom end with 18cc pistons, 9psi Allen Roots Supercharger with 75mm T/B and 90mm Lightning MAF. Seems as though the only company that makes a really nice header for my car would be Kooks. I plan on getting the ceramic-coated ones, but I’m debating whether or not the 1 5/8 mid length headers will do, or is it necessary to step up to the 1 ¾ headers? As it sits, they’re already gonna cost me a mint, so I don’t want to go with the bigger header if it’s only going to gain me a couple of horsepower. At best, the car might make 370rwph if I overdrive the M-90 a little at a later date, but as it sits, at 9psi it should run me around the 350rwhp mark.

What are your suggestions?

Even with our small cubic-inch engine, I would think with the blower the
1-3/4" headers would be optimum for street/strip. If you don't plan on going to the track, the 1 5/8" primaries should keep the torque numbers up and keep the powerband a hair lower for a better feel on the street.

 

[Gearbanger 101]

Even with our small cubic-inch engine, I would think with the blower the
1-3/4" headers would be optimum for street/strip. If you don't plan on going to the track, the 1 5/8" primaries should keep the torque numbers up and keep the powerband a hair lower for a better feel on the street.

Well, it won’t be seeing much time at the strip, but I figured that the 1 ¾ inch weren’t going to hurt low end torque a lot, considering I’m running a positive displacement blower and 3.73 gear. I just basically didn’t want to drop the extra $100.00 on the larger diameter pipes if it really wasn’t necessary.