Maximize NA Power: 4-1 Stainless Steel KA24DE Headers & Downpipe

If you're building an S13, you already know the factory cast iron exhaust manifold is a massive bottleneck. The Flashark KA24DE headers and downpipe combo is engineered specifically to fix that. Designed for the 1991-1994 Nissan 240SX 2.4L DOHC, this 4-1 stainless steel exhaust system dramatically reduces backpressure, giving your KA engine the breathing room it needs to make real naturally aspirated (NA) power.

By pairing precision mandrel-bent tubes with smooth transitions, this setup maximizes exhaust scavenging. The result? A sharper throttle response, noticeable mid-to-top-end horsepower gains, and an aggressive exhaust tone that actually sounds like a proper JDM build.

Why Upgrade Your 240SX Exhaust?

• Optimized Flow (4-1 Design): Unlike the restrictive factory KA24DE exhaust manifold, our 4-1 tubular header design merges all four cylinders into a single collector. This optimizes exhaust gas velocity, ideal for peak horsepower on the track or street.
• Direct Bolt-On Fitment: No cutting or custom fabrication required. This header and downpipe system mounts perfectly to the S13 chassis and lines up with most aftermarket 240SX exhaust setups.
• Built to Last: Constructed from mirror-polished stainless steel to resist corrosion and handle extreme exhaust gas temperatures (EGTs).
• O2 Sensor Ready: Includes a pre-welded O2 sensor bung so your ECU maintains proper air/fuel ratios without throwing check engine lights.

Specifications:

• Brand Name: Flashark
  
• Certificate: ISO9001:2000
  
• Application: Exhaust Header & Downpipe
  
• Material: Stainless Steel
  
• Surface: Mirror Polish
  
• Placement on Vehicle: Front (Replaces factory header and downpipe)
  
• Header Inlet / Outlet Size (IN): 1.75" / 2.5"
  
• O2 Sensor Bung Included: Yes
  
• Header Style: 4-1 Exhaust System

Tuner's Guide: Headers vs. Downpipe vs. Exhaust Manifold

We get a lot of questions about exhaust terminology. Here is what you need to know for your KA24DE build:

• Exhaust Manifold vs. Header: The stock KA24DE exhaust manifold is a heavy, cast-iron log. It's cheap to manufacture but terrible for airflow. A header (like this one) uses individual, equal-length steel tubes for each cylinder. It's lighter and forces exhaust gases out faster, eliminating exhaust turbulence.
• Headers vs. Downpipe: The header bolts directly to the engine block to collect exhaust gases. The downpipe connects the bottom of the header to the rest of your exhaust system (usually the catalytic converter or test pipe). Because our kit includes both the KA24DE header and the downpipe, you won't have to worry about mismatching flanges or hunting for separate parts. You get a complete, leak-free front exhaust solution.