Product description
T3 Exhaust Manifold for 12V Cummins 1989–1998 | 3-Piece Expansion Design | CARB Exempt
The Diesel Power Source® T3 exhaust manifold for 1989–1998 Dodge Ram trucks with the 5.9L 12-valve Cummins engine is a direct bolt-on replacement that flows 23% more than the factory manifold. This 3-piece expansion joint design is cast from nickel-laced ductile iron, CFD designed and flow-tested, and includes three pre-tapped ports for pyrometer and boost pressure fittings. It fits both 1st gen (1989–1993) and 2nd gen (1994–1998) 12V trucks with T3 flange turbochargers.
This manifold is CARB exempt with an Executive Order (EO) number, making it legal for use in California. It replaces OEM part number 3911349 and is one of the best first performance upgrades for any 12V Cummins work or tow truck.
Why the Stock 12V Manifold Fails
The factory 12V Cummins exhaust manifold is a single-piece casting that is prone to cracking over time due to thermal cycling. Every heat-up and cool-down cycle stresses the rigid casting, and eventually cracks develop — usually at the ends where thermal expansion is greatest. Cracked manifolds leak exhaust, reduce turbo efficiency, raise EGTs, and create an exhaust smell in the cab.
The DPS 3-piece expansion joint design solves this by allowing each section of the manifold to expand and contract independently. The expansion joints absorb thermal stress instead of transferring it to the casting, eliminating the cracking issue that plagues both factory and single-piece aftermarket manifolds.
Dedicated 12V Rectangular Port Casting
Most aftermarket manifold manufacturers cast their manifolds using a 24V round-port mold and then machine the ports to fit the 12V rectangular port head. This creates smaller, restricted port openings and poor exhaust flow transitions at the head flange.
The DPS 12V manifold uses a dedicated rectangular port mold designed specifically for the 12V head. The port geometry matches the 12V exhaust ports from the factory head to the collector, delivering unobstructed flow through the entire manifold. This is one of the primary reasons the DPS manifold outflows competitors that use adapted 24V castings.
**DOES NOT INCLUDE MANIFOLD HARDWARE/GASKETS**
