Skunk2 Alpha Series Header for 06-11 Civic Si

Skunk2 Alpha Series Header - 2006-2011 Honda Civic Si / K20Z3 & K24 Swap

Want more power from your 8th gen Civic Si? The Skunk2 Alpha Series header replaces your factory header with a 4-2-1 Tri-Y equal-length header. Your factory header's got short, unequal-length primaries and a restrictive cat. The Skunk2 header's got long, equal-length primaries and a 2.5" collector with no cat. That means better exhaust flow, which means more power everywhere in the RPM range. You'll feel the difference in mid-range torque and throttle response. If you're modding your K20Z3 Civic Si or you're doing a K24 swap, you need a header.

Here's Why You Need a Header

Your factory header's restrictive. The primaries are short and unequal length, which means exhaust pulses interfere with each other and you lose power. The factory cat's even more restrictive. It chokes your exhaust flow, especially at high RPM. When you replace your factory header with the Skunk2 Alpha header, you're getting longer, equal-length primaries that reduce exhaust pulse interference. The 4-2-1 Tri-Y design merges the primaries in pairs, which smooths out your power curve and gives you more mid-range torque. The 2.5" collector flows way more exhaust than your factory header, so you're making more power at high RPM too.

4-2-1 Tri-Y Design with Equal-Length Primaries

The Skunk2 Alpha header uses a 4-2-1 Tri-Y design. That means your four exhaust ports merge into two collectors, then those two collectors merge into one final collector. The primaries are equal length, which means exhaust pulses from each cylinder arrive at the collector at the same time. That reduces interference and makes your exhaust scavenging more efficient. You're pulling more exhaust out of your cylinders, which means more fresh air getting in on the next intake stroke. That's more power.

Works with K20Z3 and K24 Swaps

The Skunk2 Alpha header fits 8th gen Civic Si with the factory K20Z3 engine. It also fits K24 swaps if you're swapping a K24 into your 8th gen Civic. The header works with stock engine mounts and a CR-V rear engine mount. If you're doing a K24 swap, you don't need custom engine mounts to make this header fit. It bolts on.

2-Bolt Flange - Check Your Exhaust

The Skunk2 header uses a 2-bolt flange at the collector. Make sure your exhaust system or test pipe uses a 2-bolt flange. If your exhaust has a 3-bolt flange (like some aftermarket exhausts do), you'll need a 2-bolt to 3-bolt adapter to connect them. Don't try to force a 3-bolt exhaust onto a 2-bolt header. You'll crack your flange or leak exhaust. Get the right adapter or get an exhaust with a 2-bolt flange.

Race-Only - No Cat

This header's race-only. It eliminates your catalytic converter. That means it's not legal for street use in California or any state with emissions testing. If you're in a state with no emissions testing and you don't care about passing smog, you can run it on the street. If you're in California or you need to pass emissions, don't buy this header. It'll fail emissions and you'll get a ticket. This is a race header for off-road use.

What You Get

• Skunk2 Alpha Series 4-2-1 header
• Equal-length Tri-Y primary design
• 2.5" collector outlet with 2-bolt flange
• No catalytic converter (race-only)
• Compatible with K20Z3 and K24 engines
• Works with stock engine mounts and CR-V rear mount
• All mounting hardware and gaskets included

Fits Your Car

• 2006-2011 Honda Civic Si (8th gen, K20Z3)
• 2006-2011 Acura CSX (K20Z3)
• 2006-2011 Honda Civic Si with K24 swap

Compatible Engines

• K20Z3 (2006-2011 Civic Si, Acura CSX)
• K24 (swapped into 8th gen Civic Si)

Note: This header's for off-road and race use only. It eliminates your catalytic converter, so it's not legal for street use in states with emissions testing. You'll fail emissions if you try to smog your car with this header. If you're in California, don't buy this header unless it's going on a dedicated race car that's never driven on the street. The header uses a 2-bolt flange. Make sure your exhaust or test pipe uses a 2-bolt flange. If your exhaust has a 3-bolt flange, you'll need a 2-bolt to 3-bolt adapter. Don't force a mismatched flange connection. You'll crack the flange or get exhaust leaks. Get your car tuned after you install this header. Your ECU's not programmed for the increased exhaust flow, so you'll need to adjust your fuel and ignition maps to make proper power.