Header Adapter Plates, Flange Spacers & Kits

What Are Header Flanges and Header Adapter Plates?

Header flanges bolt your headers to the heads, and a header adapter plate sits between the two to relocate the bolt pattern. Race headers with primary tubes larger than about 1-3/4" can partially cover the original header bolt holes. When that happens, the flange bolts can't line up with the head.

An adapter plate solves that problem. It bolts to your cylinder heads with countersunk bolts or screws, so the header sits flush against the plate. Threaded holes in the plate give the header its own mounting points.

The exhaust openings can be port-matched to the head's exhaust ports. Large-tube headers with a Stahl or other non-standard bolt pattern need adapter plates to fit standard heads. If you're still comparing parts, read up on the difference between exhaust manifolds and headers.

When Do You Need Header Spacers or an Exhaust Spacer?

You need header spacers when your headers sit too close to chassis, steering, or suspension parts. A header spacer is a metal flange that fits between the head and the header. It pushes the header outward to give you more clearance.

Spacer thickness typically ranges from 3/8" to 5/8", so you can pick the offset your build needs. An exhaust spacer is a common fix when long-tube headers crowd the frame, steering shaft, or suspension components. You'll also see this part listed as an exhaust manifold spacer.

Before you order, measure how much extra clearance you need at the tightest point. If you haven't settled on a header style yet, compare long-tube vs. shorty headers first. Keep in mind that a spacer adds another joint, so plan on a gasket for each face.

Header Flange Kit Options by Engine Family

A header flange kit is cut for one engine family and port shape, so start with your engine. Stainless Works makes most of the engine-specific flanges in this category. Here are the options you'll find:

• Small-block Chevy 265-400 header flange kits from Patriot Exhaust
• Small-block Chevy 262-400 flange kits with tube stubs from Hooker Headers
• Stainless Works big-block Chevy flanges with 2" and 2-1/8" ports
• 5.7L Hemi flanges with a 1-3/4" port
• Big-block Ford flanges with a 2-1/4" flat oval port
• 4.6L 3V modular Ford flanges with a 1-5/8" round port
• 5.0L Coyote and 5.2L Ford flanges with a 2" round port
• LS1/LS6 flanges with a 1-7/8" round port
• Exhaust block-off plates for small-block Chevy engines

Each exhaust header flange matches a specific port size and shape, so a big-block flange won't fit a small-block head. Confirm your engine and head before you add a kit to your cart.

Collector Flanges and Exhaust Hardware

A collector flange connects your header collector to the rest of the exhaust system, and this category covers several bolt styles. Pick the flange that matches your collector diameter and the pipe it joins. Measure your collector outlet first, since flanges and rings are listed by diameter.

Collector and exhaust hardware options in this category include:

• 3" and 3.5" collector flanges from Pypes Performance Exhaust
• 3-bolt collector flanges in 3" and 3.5" sizes
• 2-bolt collector flange kits from Patriot Exhaust
• 3" ball-and-socket exhaust flange kits from Hedman
• Heavy-duty collector flange rings in 2-1/2" and 3-1/2" I.D.
• Collector tether kits
• U-tab kits for drag collectors

If you're building out the rest of the system, browse header collectors and reducers to match your flange size. Then pick up header and collector bolts sized for your flanges.

How to Choose and Install the Right Header Flanges

To choose the right header flanges, confirm your engine family, port shape, and tube O.D. before you order. Fitment differs by engine family. Port shapes include round, oval, D-port, and flat oval.

Measure the outside diameter of your primary tubes and compare it to the flange port size. Our guide on how to measure exhaust component diameter walks you through it. If your tubes are larger than about 1-3/4", check whether they'll cover the head's bolt holes.

When you install an adapter plate, use countersunk fasteners so the header sits flush. Plan on two gaskets: one between the head and plate, and one between the plate and header. If you need clearance instead, size your spacer before you bolt anything down.

Shop all header flanges, adapter plates, and spacers here, or browse the full lineup of headers and exhaust manifolds for your next build.