Flowmaster American Thunder Exhaust System

Built to howl. Tuned to win. The Flowmaster® American Thunder Cat-Back (PN 818169) brings classic Flowmaster authority with daily-drive manners. It’s a mandrel-bent 409S stainless system feeding a Super 40 Series muffler and finishing in dual 4.5" ceramic-black tips that fill the bumper cutouts the way Ford should’ve.

Why it hits

• Real gains: Dyno showed +18 hp / +14 lb-ft at the wheels vs. stock (max increases).

• Free-flowing 3" tubing: Mandrel-bent 16-gauge 409 stainless for flow and durability.

• Super 40 voice: Deep, aggressive-to-moderate tone with head-turn on throttle, calm on cruise.

• Factory-clean fit: Uses OEM hanger locations, includes hardware/hangers—no welding required.

• Proper finish: Dual 4.5" rolled, single-wall, angle-cut tips in ceramic black stainless—fills the cutouts better than OEM.

• Backed by Flowmaster: Limited Lifetime Warranty on stainless components.

What it fits

• Ford F-150 with factory dual-exhaust bumper cutouts—works with PowerBoost and standard gas trucks (select your year/engine/wheelbase on the product page for exact part mapping).

Sound

• Idle/Cruise: Deep muscle, controlled cabin presence.

• Wide-Open Throttle: Classic American Thunder bark—authoritative without being obnoxious.

Install notes

• Type: Cat-Back, single in / dual out, dual rear exit (driver & passenger)

• Driveway friendly: ~2 hours, hand tools, no welding

• Keep all packaging until you’ve verified fitment. Photograph your unbox/install for records and support.

Tech specs

• Material: 409S stainless steel (16-ga)

• Primary pipe diameter: 3.0" mandrel-bent

• Muffler: Super 40 Series, single inlet / dual outlet (qty 1)

• Exhaust type: Single system with dual rear exits

• Tips: (2) 4.5" round, rolled, single-wall, angle-cut, ceramic-black stainless

• Includes: Muffler, pipes, tips, hardware, factory-style hangers, instructions

• Muffler delete: No

• Required welding: No

• Estimated install time: 2 hours

• Sound level: Aggressive / Moderate

• Warranty: Limited Lifetime (manufacturer)

Builder’s checklist

• Confirm year/engine/drive/bed & wheelbase and factory dual-exit bumper before ordering.

• Test-fit from front to rear before tightening clamps.

• Re-torque after heat cycles.

• Pair with intake/tune for best net gains.

Fitment questions? Shoot us a line! We’ll sanity-check your build before you buy.


Prop 65 WARNING: While this product is safe unaltered, welding can expose chemicals in this product that can expose you to chemicals known to the State of California to cause cancer and/or birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.