4BT / 3.9L Cummins 24V Exhaust Manifold Upgrade (T3)
This upgraded exhaust manifold is built for 4BT and 3.9L Cummins 24-valve engines used in industrial applications, equipment, and swap builds. The stock manifolds are known to crack, warp, and leak under heat and load. This replacement design offers improved durability, better airflow, and more stable turbo performance for stock setups and future upgrades.
*This is not a Factory Fitment Replacement, This is an AFTERMARKET replacement manifold.
Built for Reliability and Performance
- Improves turbo responsiveness and efficiency compared to restrictive factory designs.
- Reduces exhaust leaks that hurt boost and power.
- Engineered to better handle thermal cycling, towing, and high-load applications.
- Works well for stock replacement, tuning, or turbo upgrade paths.
Key Features
- T3 Turbo Flange: Compatible with factory and upgraded turbochargers.
- Heavy-Duty Casting: Designed to resist cracking and heat fatigue over long service life.
- Improved Flow Design: Helps reduce backpressure and support better exhaust efficiency.
- Direct Bolt-On: Uses standard mounting positions for straightforward installation.
- Works With ISB and QSB Engines: Ideal for equipment, swaps, and performance builds.
Fitment & Applications
- Engine: Cummins 4BT / 3.9L (24-Valve)
- Turbo Flange: T3
- Compatible Platforms:
- Cummins ISB 4BT
- Cummins QSB 4BT
- Truck and equipment applications
- Custom swap builds (Jeep, classic trucks, off-road, and specialty vehicles)
OEM Cross References
This manifold replaces several factory exhaust manifold part numbers used on 24V Cummins 4BT and ISB/QSB applications.
**Please check fitment carefully before purchase, verify against your original part number and application before ordering.
Ideal Applications
- Stock replacement for cracked or leaking factory manifold
- Performance tuning with better airflow headroom
- Turbo upgrade or retrofit projects requiring a T3 mounting pattern
- 4BT swap vehicles needing durability and fitment compatibility
In most applications, yes. Even though the manifold bolts to the engine, turbo plumbing, downpipe angles, charge piping, and wastegate routing may require custom work depending on space and components used.
Yes. These manifolds are compatible with many industrial, generator, agricultural, and equipment versions of the 4BT, as long as engine configuration and turbo style match.
These manifolds are commonly used in 4BT swap platforms, including but not limited to: Jeep Wrangler YJ, TJ, and JL conversions Ford Bronco and Ranger swaps Square-body Chevy trucks Land Rovers and off-road builds Classic cars like Camaros and Mustangs Freightliner MT45 / MT55 step vans Grumman Olson UPS/FedEx trucks Mini school buses and shuttle buses Skid steers, trenchers, and forklifts Small boats and marine applications Military Humvees, trailers, and gensets Because many of these builds are custom, layout and turbo positioning should be planned in advance.
