SP Concepts Big Bore Performance Exhaust

For Harley-Davidson M8, Twin Cam, Dyna, FXR & Bagger Models

The SP Concepts Big Bore 4.5” Exhaust is built for riders who demand real horsepower gains, hard-hitting torque, and race-proven durability. Designed to support everything from mildly built motors to full big-bore monsters, this system delivers strong bottom-to-mid range power while flowing enough air to support engines from 88” all the way up to 143” when properly tuned.

Handcrafted in the USA by SP Concepts, this exhaust is engineered for aggressive riding, performance baggers, club-style Dynas, and high-output Harley builds where flow, heat control, and strength matter.

Available in Standard and "The Works" edition which features a hand cut and welded pie cut design: 

• Precisely pie cut and TIG welded back together by hand

• A meticulously pain staking process but the results are a work of art in the end.

More SP Concepts exhausts HERE. 

Why Run the SP Concepts Big Bore 4.5” Exhaust?

Most exhaust systems choke high-output Harley motors or sacrifice low-end torque. The SP Concepts Big Bore system is engineered to do the opposite—increase torque and horsepower across the usable RPM range while maintaining strong exhaust velocity.

• Designed for big-inch and high-compression Harley motors

• Excellent bottom-to-mid range torque gains

• Supports aggressive cam and displacement upgrades

• Built to handle heat, abuse, and hard riding

Key Features

4.5” High-Flow Rolled Cone Muffler

• Stepped baffle design from 2¼” to 2½”

• Optimized exhaust scavenging

• Improves throttle response and mid-range power

• Tuned for street and performance applications

Stepped Stainless Steel Headers

• .065 wall stainless steel headers

• Stepped from 1¾” → 1⅞” → 2” at the collector

• Designed to improve exhaust velocity and power delivery

• Handles high heat from big bore and high-output engines

Precision Craftsmanship

• Fully hand TIG welded from top to bottom

• Machined stainless steel header collars

• Built for long-term durability and consistent performance

Sensor & Tuning Friendly

• 18mm O2 bungs with included 12mm adapters

• Compatible with stock O2 sensors or autotune systems

• Ideal for EFI tuning and performance engine management

Complete Installation Package

• Includes a full hardware kit

• Everything needed for proper installation

• Built for clean fitment and secure mounting

Fitment

✔ Compatible with:

• M8 Bagger

• M8 Softail

• Twin Cam Dyna

• Twin Cam Bagger

• FXR

✔ Engine Compatibility:

• Properly tuned, supports 88”–143” engines

⚠️ Professional tuning is strongly recommended to achieve maximum performance and reliability.

Perfect For Riders Searching For:

• Harley big bore exhaust system

• M8 performance exhaust

• SP Concepts Harley exhaust

• High horsepower Harley exhaust

• Performance bagger exhaust

• Dyna big bore exhaust

• FXR performance exhaust system

What You’ll Feel After the Upgrade

• Stronger bottom-end torque

• More usable mid-range power

• Improved throttle response

• Better flow for cam and big bore builds

• A true performance exhaust tone—not just noise

This exhaust isn’t about looks alone—it’s built to make power where it counts.

Video showing how to clean your stainless exhaust:

https://youtu.be/gfjufIlpocU?si=dRc_9Ph2ub8czT8O