GM 3.5L Vortec 3500/3700 Manifold Flange (304 SS)

PRE-ORDER NOW, SHIPPING MID JANUARY!

Building a turbo setup or custom header for the GM Atlas 3500/3700 inline-5 (3.5L platform) starts with a solid flange. This is a raw, weld-ready exhaust manifold flange cut from 1/2" thick 304 stainless steel and left in a mill finish so you can port, match, and surface it exactly how your build needs.

Features

• Application: GM Atlas 3500/3700 Inline-5 (3.5L) exhaust/manifold builds

• Material: 304 stainless steel

• Thickness: 1/2" (12.7 mm)

• Finish: Raw mill finish (uncoated)

• Cut Process: Precision laser cut

• Use Cases: Turbo manifolds, NA headers, custom downpipes, fab projects

• Weld-Ready: Ideal for TIG/MIG stainless fabrication

Why 304 Stainless?

304 is a proven exhaust material because it offers:

• Strong corrosion resistance for street and performance use

• Good high-temp durability for manifolds and turbo setups

• Excellent weldability with common stainless filler metals

Important Note on Flatness (Please Read)

These flanges do arrive with a slight bow/warp.
That’s normal for laser-cut 1/2" stainless — the cutting heat can introduce mild movement. This is common across the industry and not a defect.

After welding, flanges should be surfaced flat to guarantee sealing. We recommend one of the following:

• Block sand flat on a known-flat surface, or

• Machine/plane flat (best for high-boost or high-heat builds)

Welding heat can add a bit more movement, so final surfacing is standard practice on performance manifold builds.