Cummins 4089649 — Genuine Upper Engine Gasket Set for 5.9L 12-Valve (6BT)

MPN: 4089649  |  Also Known As: upper engine gasket kit, head set (standard thickness)

Genuine Cummins upper engine gasket set for a complete top-end refresh on 1989–1998 5.9L 12-valve (6BT) applications. Includes the standard-thickness head gasket (P/N 3283335) and the critical OE seals needed to reassemble the cylinder head, intake, exhaust, and injector interfaces. Ideal for stock rebuilds and leak fixes while maintaining OEM reliability.

Features & Benefits

• Complete top-end sealing with OE gaskets, O-rings, and washers for the 5.9L 12V.
• Standard-thickness MLS head gasket (3283335) for factory-spec builds.
• Direct-fit OEM components engineered for durability and leak prevention.
• Ready-to-install kit reduces parts chasing and speeds up reassembly.
• Backed by Cummins quality for fit, function, and long service life.

Verified Fitment (Automotive)

Industrial/Off-Highway: B-Series 5.9L (non-certified/6B) plus select ISB/QSB families—verify by ESN before ordering.

Specifications

• Type: Upper engine gasket set (standard-thickness head gasket)
• OE Kit Part Number: 4089649
• Head Gasket Included: 3283335 (standard thickness)
• Representative Contents (IDs): 3283335 head gasket; 3929881 exhaust manifold gaskets (x6); 3930906 valve cover gaskets (x6); 3957912 valve stem seals (x12); 3900808/3923261/3930324/3937142 injector seals; 3919358 injector sleeves (x6); 3901356 turbo gasket; 3938152 intake cover gasket; 3923331 thermostat housing gasket; 3902425, 3963988 sealing washers, and more.
• Quantity: 1 kit per engine

What’s In The Box

• (1) Genuine Cummins Upper Engine Gasket Set (4089649) with standard-thickness head gasket (3283335)
• All associated OE O-rings, seals, and gaskets required for the top end (see contents above).

Installation Tips

• Measure piston protrusion and check deck/head flatness; choose head gasket thickness accordingly if outside factory spec.
• Clean threads, chase head bolt holes, and follow OE torque sequence/angles.
• Inspect mating surfaces and replace any warped/damaged components.
• After first heat cycle, perform fluid checks and re-inspect for leaks.

FAQ

WILL THIS FIT MY 1989–1998 5.9L 12-VALVE CUMMINS?

Yes—4089649 is specified for 5.9L 12-valve applications in 1989–1998 Ram 2500/3500 (verify by VIN/ESN).

DOES THIS KIT INCLUDE A HEAD GASKET, AND WHAT THICKNESS?

Yes—this set includes the standard-thickness head gasket (3283335). If your engine has been decked or piston protrusion is out of spec, use the correct thickness grade.

WHAT’S THE DIFFERENCE BETWEEN UPPER AND LOWER GASKET SETS?

The upper set covers the cylinder head and top-end sealing (head gasket, valve cover, intake/exhaust, injector seals). The lower set covers oil pan, front/rear covers, etc.

IS THIS A GENUINE CUMMINS KIT?

Yes—OE Cummins kit 4089649 with OEM-spec contents and materials.

CAN I REUSE MY HEAD BOLTS?

We recommend new bolts or studs during a head-off service for best clamping and reliability, especially on higher-mileage engines.