Secure maximum machine uptime and ultimate reliability in the most severe heavy equipment applications. The Workhorse Plus tier cylinder head for Kawasaki 70Z-II, 70Z-III, and 70Z-IV wheel loaders is engineered for operations where equipment failure and field downtime are completely unacceptable. Assembled using a renewed, pressure-tested OEM core and premium internal components, this top-tier cylinder head features extreme-duty upgrades to handle maximum cylinder pressures, intense thermal cycles, and continuous peak-torque demands in brutal operating environments.

Upgrades Over the Workhorse Tier: Heavy-Duty Valve Springs

While the Workhorse tier introduces a critical O-ringed deck, the Workhorse Plus adds premium, heavy-duty valve springs and upgraded retainers. This severe-duty valvetrain package prevents valve float and spring fatigue during sustained full-load operation and high exhaust backpressures, ensuring absolute valvetrain stability and reliable valve tracking when your loader is pushing its absolute limits.

Premium Component Breakdown

• Remanufactured Casting: Built from a premium OEM core casting that has undergone rigorous diagnostic testing and is machined to like-new industrial specifications.

• Precision O-Rings: To combat severe thermal expansion common in heavy earthmoving, precision O-rings are cut directly into the deck surface. This mechanical modification locks the head gasket securely in place, completely eliminating the risk of combustion leaks under extreme load.

• New Valves: Equipped with all-new, high-quality intake and exhaust valves, verified for precise seating and clearance.

Key Features and Heavy-Duty Fixes

This severe-duty head undergoes an intense inspection and upgrade protocol to guarantee every critical industrial metric is met.

• 40 PSI Pressure Testing: Following the machining process, every cylinder head is pressure-tested at 40 PSI to verify zero structural leaks and absolute casting integrity.

• Blow-Proof Plugs: Threaded, blow-proof plugs are installed into the top of the head for superior safety, replacing factory pressed-in freeze plugs that regularly fail during severe thermal spikes.

• Final Quality Control: The head undergoes a meticulous final cleaning and rigorous quality control checking. A comprehensive specification sheet is generated, using a profilometer to record:

  • Valve Recessions

  • Stem Heights

  • Installed Spring Heights

  • Spring Pressures

  • Keeper and Lock Positions

  • Roughness Average (RA) Surface Finish

Precision Machining Process

Choate Engineering Performance incorporates structural updates to resolve common factory vulnerabilities of the 5.9L industrial cylinder head, significantly extending operational lifespan:

• Optimal Sealing Surface: The deck is resurfaced to strictly meet or exceed OEM specifications for Roughness Average (Ra), maximizing the sealing surface performance for the head gasket.

• Valve Train Geometry Alteration: The head is custom blueprinted to adjust valve height and valve recession, optimizing geometry for high-stress industrial applications.

• Lifter and Camshaft Longevity Fix: Valve stem heights are precisely machined to remove excessive preload on the lifters, a critical adjustment that dramatically reduces wear and extends the service life of both lifters and the camshaft.

• Optimized Flow and Sealing: Valve seats are cut with an industrial three-angle profile to optimize engine efficiency and ensure an airtight seal.

• Valve Prep: Valves are reground and margins are meticulously inspected to guarantee proper sealing against the new seats.

• All-New Wear Parts: New valve stem seals, valve seats, valve guides, and injector cups are installed across the entire assembly.

Meticulous Cleaning and Prep Process

Our manufacturing protocol begins with an intensive cleaning and stress-relieving process to ensure a flawless casting:

• Magnetic Particle Inspection (MPI): Every single core is subjected to MPI testing to scan for microscopic cracks or subsurface structural imperfections.

• Thermal Stress Relieving: Castings undergo a thermal baking process in a specialized furnace to eliminate residual industrial oils and grease by converting them to ash.

• Material Relaxation: The head is shot-blasted to strip away rust and scale. This vital step relaxes the cast iron before any precision machining takes place.

• Thread Restoration: All broken factory bolts and studs are professionally removed, leaving all holes clean, chased, and ready for head studs or bolts.