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The Stainless Works M242HCAT is a set of long-tube headers with high-flow catalytic converters built for the 2015-2026 Ford Mustang GT with the 5.0L Coyote V8. Using 2-inch 304 stainless steel primary tubes and a 3-inch collector with integrated merge spike, the M242HCAT maximizes exhaust flow for forced induction builds and high-output naturally aspirated applications where maximum primary tube diameter is the priority. The factory connect outlet bolts directly to the OEM cat-back exhaust at the 2-1/4-inch connection point with no cutting required. Handmade to order in Streetsboro, Ohio and backed by a lifetime warranty.
What's Included
- Driver-side long-tube header
- Passenger-side long-tube header
- 2 high-flow catalytic converters
- 2 lead pipes
- 4 band clamps
- 4 O2 sensor extensions
- 16-piece bolt kit
- RTV sealant
- Installation instructions (covering 2015-2017, 2018-2023, and 2024 plus model years)
2-Inch Primaries: Built for Boost and High-RPM Flow
The M242HCAT uses 2-inch primary tubes, the largest diameter Stainless Works offers for the S550 and S650 Mustang GT platform. Larger primaries reduce exhaust velocity slightly at low RPM but dramatically increase peak flow capacity at high RPM and under forced induction. This makes the M242HCAT the correct choice for supercharged and turbocharged Coyote builds, as well as naturally aspirated builds targeting maximum top-end power. For street-driven naturally aspirated builds where low-to-mid RPM response matters more, the 1-7/8-inch M24HCAT is typically the better choice.
Factory Connect: True Bolt-On with Zero Cutting
The factory connect outlet on the M242HCAT is sized at 2-1/4 inches to mate directly to the OEM Ford cat-back exhaust system. No modifications to the existing cat-back are required. If you are running a non-Stainless-Works aftermarket cat-back with a 3-inch inlet, see the M242H3CATLG (2-inch primaries, aftermarket connect) instead.
Fitment for 2015-2026 Ford Mustang GT
The M242HCAT fits the 2015-2026 Ford Mustang GT with the 5.0L Coyote V8 only. It is not compatible with the EcoBoost four-cylinder or the Shelby GT500 supercharged V8, which use different exhaust configurations. Confirm your engine is the 5.0L V8 before ordering. An ECU retune is strongly recommended after installation.
| Year | Make | Model | Trim | Engine |
|---|---|---|---|---|
| 2015 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2016 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2017 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2018 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2019 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2020 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2021 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2022 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2023 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2024 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2025 | Ford | Mustang | GT | 5.0L Coyote V8 |
| 2026 | Ford | Mustang | GT | 5.0L Coyote V8 |
Full Specifications
| Specification | Detail |
|---|---|
| Part Number | M242HCAT |
| Header Type | Long-Tube Headers with High-Flow Catalytic Converters |
| Primary Tube Diameter | 2 in. |
| Collector Diameter | 3 in. with Integrated Merge Spike |
| Flange Thickness | 3/8 in. |
| Material | 304 Stainless Steel, CNC Mandrel-Bent, TIG Welded |
| Connection Point | Factory Connect, 2-1/4 in. outlet (fits OEM cat-back, no cutting) |
| Catalytic Converters | High-Flow, 2 included |
| O2 Sensor Extensions | 4 included |
| Installation Type | Bolt-On, No Welding or Cutting Required |
| ECU Tune Recommended | Yes, strongly recommended after installation |
| Country of Origin | Made in USA (Streetsboro, Ohio) |
| Warranty | Lifetime Warranty |
| Build Time | Built to order, approximately 4 weeks |
Not Street Legal in California
The M242HCAT does not carry a CARB Executive Order number and is not legal for street use in California or other CARB-adopting states. It is intended for track use or street use in non-CARB states. Verify local regulations before ordering.
Warranty and Factory Coverage
Stainless Works backs the M242HCAT with a lifetime warranty on materials and workmanship. Under the federal Magnuson-Moss Warranty Act, an aftermarket part cannot void your factory warranty unless the dealer proves the part directly caused the specific failure claimed.
Compare: Full Stainless Works S550 and S650 Mustang GT Header Family
Stainless Works offers six header configurations for the 2015-2026 Mustang GT, combining two primary tube sizes with three connection point options. Choose the right combination for your build and your existing cat-back exhaust:
| Part Number | Primary Tube | Connection Point | Best For |
|---|---|---|---|
| M24HCAT | 1-7/8 in. | Factory Connect (2-1/4 in.) | Street NA builds retaining OEM cat-back |
| M24H3CAT | 1-7/8 in. | Performance Connect (3 in.) | Stainless Works cat-back pairing |
| M24H3CATLG | 1-7/8 in. | Aftermarket Connect (3 in.) | Non-SW aftermarket cat-back (MBRP, Corsa, etc.) |
| M242HCAT | 2 in. | Factory Connect (2-1/4 in.) | Forced induction or max-flow NA, OEM cat-back retained |
| M242H3CAT | 2 in. | Performance Connect (3 in.) | Forced induction with Stainless Works cat-back |
| M242H3CATLG | 2 in. | Aftermarket Connect (3 in.) | Forced induction with non-SW aftermarket cat-back |
About Stainless Works
Stainless Works has been handcrafting performance exhaust systems in Streetsboro, Ohio since 1989. Every header set is built to order from 304 stainless steel using CNC mandrel bending and full TIG welding. Fitment engineering is done in-house on actual production vehicles and backed by a lifetime warranty.
Frequently Asked Questions
What is the difference between the M242HCAT and the M24HCAT for the 2015-2026 Mustang GT?
The M242HCAT uses 2-inch primary tubes and the M24HCAT uses 1-7/8-inch primaries. Both use the factory connect outlet and include high-flow cats. The 2-inch primaries on the M242HCAT deliver higher peak flow at top RPM and under boost, making them the preferred choice for forced induction builds. The 1-7/8-inch M24HCAT produces stronger low-to-mid RPM torque, which is generally preferred for naturally aspirated street builds.
Does the M242HCAT require cutting my existing cat-back?
No. The factory connect outlet is sized at 2-1/4 inches to slip directly onto the OEM Ford cat-back exhaust. No cutting, welding, or modification to the existing system is required. If you are running a 3-inch aftermarket cat-back, see the M242H3CATLG instead.
Does the M242HCAT fit the 2024 and newer S650 Mustang GT?
Yes. Stainless Works lists this header as compatible through 2026 and includes separate installation instructions for the 2024-plus S650 platform, which has different underhood access than the S550 (2015-2023).
Is a tune required after installing the M242HCAT?
An ECU retune is strongly recommended. Long-tube headers significantly change exhaust scavenging dynamics and O2 sensor readings. Running without a tune after installation may trigger check engine lights from the relocated catalysts and leave significant power gains on the table.
Will the M242HCAT fit with my existing aftermarket cat-back?
Only if your aftermarket cat-back has a 2-1/4-inch inlet connection point (same as OEM). Most aftermarket cat-backs use a 3-inch inlet, which requires the M242H3CATLG (aftermarket connect) variant instead. Check your cat-back inlet diameter before ordering.
Is the M242HCAT legal in California?
No. The M242HCAT does not hold a CARB Executive Order number and is not street legal in California or other CARB-adopting states. It is for track use or use in states where it is permitted.
Will these headers void my Ford factory warranty?
Under the federal Magnuson-Moss Warranty Act, a dealer cannot void your factory warranty simply because you installed aftermarket headers. They must prove the part directly caused the specific failure being claimed.
How long does it take to receive the M242HCAT?
Each set is built to order in Stainless Works' Ohio facility. Current lead time is approximately four weeks from order date.
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