The Dorman 674-746 is an OEM-style replacement driver-side (left-hand) exhaust manifold engineered specifically for 1999–2003 Ford F-250, F-350, F-450, and F-550 Super Duty trucks, 2000–2003 Ford Excursions, and 1999–2003 Ford E-Series vans equipped with the 7.3L Powerstroke diesel engine. Precision-cast from heavy-duty ductile iron to replicate factory OE dimensions and runner profiles, this manifold is built to withstand extreme thermal expansion, sustained high exhaust gas temperatures (EGTs), and severe engine harmonics without warping, cracking, or leaking. It features precision-machined cylinder head port sealing faces and a factory-flanged rear discharge port engineered to mate directly to the driver-side turbocharger up-pipe collector.

Audible ticking and hissing exhaust leaks under load, black carbon soot accumulation across the steering shaft, oil cooler bundle, and cylinder head, cracked runner webbing, warped sealing planes, and significant turbo spool lag caused by exhaust drive-pressure bleed-off are what this replacement manifold eliminates. Under heavy towing and frequent thermal cycling, original cast manifolds commonly warp or develop structural stress fractures, allowing critical exhaust drive energy to bleed off before reaching the turbocharger turbine wheel. The Dorman 674-746 provides an affordable, direct-fit replacement that restores full exhaust flow velocity while ensuring clearance around the steering shaft, front crossmember, and oil cooler assembly. It is packaged as a complete, installation-ready kit containing the driver-side cast manifold, replacement manifold gasket, and up-pipe flange hardware; cylinder head-to-manifold mounting bolts (Ford F4TZ-9S425-A) are sold separately.

It fits all 1999–2003 Ford Super Duty F-250, F-350, F-450, and F-550 trucks, 2000–2003 Ford Excursions, and 1999–2003 Ford E-250, E-350, and E-450 Econoline vans equipped with the 7.3L Powerstroke turbo diesel engine (driver/left-hand side only; compatible with Early 1999 and Late 1999–2003 models).

Fitment

• 1999–2003 Ford F-250 Super Duty 7.3L Powerstroke Turbo Diesel (Early 1999 & Late 1999–2003)
• 1999–2003 Ford F-350 Super Duty 7.3L Powerstroke Turbo Diesel
• 1999–2003 Ford F-450 / F-550 Super Duty 7.3L Powerstroke Turbo Diesel
• 2000–2003 Ford Excursion 7.3L Powerstroke Turbo Diesel
• 1999–2003 Ford E-250 / E-350 / E-450 Econoline Van 7.3L Powerstroke Turbo Diesel
• Direct bolt-on replacement engineered to match OE fit, runner volume, and flow characteristics
• High-strength cast-iron construction resists heat distortion, runner cracking, and fatigue
• Restores exhaust drive pressure to the turbocharger for faster spool times and lower EGTs
• Precision-machined port sealing surfaces ensure a tight seal against the cylinder head
• Includes replacement manifold gasket and up-pipe collector hardware for a complete install
• Direct replacement for OEM Ford part numbers F81Z-9431-AA, F81Z9431AA, and Navistar 1824273C1, 1827273C1
• Backed by Dorman's Limited Lifetime Warranty

Park the truck on a level surface, set the emergency brake, and disconnect both negative battery cables. Raise the front driver side, support the frame securely on an axle stand, remove the driver-side front wheel, and detach the inner plastic fender liner to gain direct, straight-on access to the manifold and cylinder head exhaust ports. Soak the eight manifold-to-head bolts and the two rear up-pipe collector flange fasteners thoroughly with high-performance penetrating oil several hours prior to removal to reduce the risk of shearing seized fasteners in the head. Unbolt the two collector flange bolts connecting the manifold to the driver-side turbo up-pipe. Using a 6-point socket and breaker bar, carefully loosen and remove the eight factory exhaust manifold bolts (avoid aggressive pneumatic impacts to protect heat-fatigued hardware). Remove the old manifold from the engine bay and thoroughly clean the cylinder head exhaust port faces using a wire brush or scraper until the cast-iron surface is completely flat, smooth, and free of carbon buildup and rust scale. Run an M10 x 1.5 thread chase tap into each cylinder head bolt hole and blow out all debris with compressed air to ensure accurate torque readings. Position the included gasket and the new Dorman 674-746 manifold against the cylinder head. Apply high-temperature anti-seize to the threads of new manifold mounting bolts, thread all eight bolts in finger-tight, and torque them in an alternating spiral sequence from the center ports outward in two stages: first to 25 ft-lbs, followed by a final pass to 35 ft-lbs (47 Nm). Connect the rear collector flange to the turbo up-pipe using the included hardware and torque to 35 ft-lbs. Reinstall the inner wheel liner and front wheel, reconnect both negative battery cables, and start the engine to verify a tight, leak-free exhaust seal.