



Keep your heavy equipment operational under the most demanding workloads. The Workhorse tier cylinder head for the Kawasaki 70Z-II, 70Z-III, and 70Z-IV wheel loader (Cummins 5.9L 12-valve engine) is specifically engineered for sustained heavy-duty industrial work, continuous duty cycles, and extreme thermal loads. Assembled using a renewed, pressure-tested OEM core combined with brand-new, high-quality internal components, this cylinder head integrates premium durability upgrades to handle elevated cylinder pressures and eliminate common field failures.
Severe industrial operation causes rapid thermal expansion, which is the leading cause of head gasket failure in heavy equipment. The Workhorse model solves this by features precision-cut O-rings machined directly into the deck surface. This mechanical modification locks the head gasket securely in place, dramatically improving sealing under high cylinder pressures and severe operating temperatures to ensure zero combustion leaks.
Remanufactured Casting: Built from a high-quality OEM core casting that has passed rigorous magnetic testing and is machined to like-new specifications.
New Valves: Equipped with new, high-quality intake and exhaust valves, inspected for proper seating, depth, and clearance.
New Valve Springs and Retainers: Utilizes brand-new valve springs matched to the rigorous requirements of industrial engines, with durable retainers and locks for secure operation during prolonged high-torque output.
New Injector Cups: Pre-installed new injector cups ensure an absolute fuel seal and prevent coolant contamination.
This head features critical performance and structural upgrades, backed by an intense inspection protocol to guarantee every industrial specification is met.
40 PSI Pressure Testing: After machining, every cylinder head is pressure-tested at 40 PSI to confirm zero leaks and ensure casting integrity.
Blow-Proof Plugs: Threaded, blow-proof plugs are installed in the top of the head for increased security and leak prevention, replacing factory pressed-in plugs that fail under thermal stress.
Final Quality Control: The head undergoes an extensive final cleaning and strict quality control inspection. A detailed sign-off sheet is generated, measuring and recording critical specifications using a profilometer, including:
Valve Recessions
Stem Heights
Installed Spring Heights
Spring Pressures
Keeper and Lock Positions
Roughness Average (RA) Finish
Choate Engineering Performance has incorporated critical modifications to address common factory vulnerabilities of the 5.9L Cummins industrial cylinder heads, drastically improving field reliability:
Optimal Sealing Surface: The deck is resurfaced to 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 alter valve height and valve recession, achieving maximum reliability under continuous loads.
Lifter Longevity Fix: Valve stem heights are precisely altered to optimize valvetrain geometry and remove excessive preload. This crucial modification decreases wear and significantly extends the life of the lifters and camshaft.
Optimized Flow and Sealing: Valve seats are cut with a precise three-angle profile to optimize 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 Components: New valve stem seals, valve seats, valve guides, and injector cups are installed across the board.
Our commitment to quality begins before machining, with an intensive cleaning and stress-relieving process to ensure a flawless starting point:
Magnetic Particle Inspection (MPI): Each core is subjected to MPI testing to thoroughly check for any cracks or subsurface imperfections.
Thermal Stress Relieving: The head undergoes a stress-relieving process in a specialized furnace to eliminate residual industrial oils and grease by turning them into ash.
Material Relaxation: The head is shot-blasted to remove rust and scaling. This crucial step relaxes the cast iron material before precision machining begins.
Thread Prep: All broken bolts and studs are professionally removed to ensure threads are clean, chased, and ready for a seamless installation.
PLEASE READ AND FILL OUT THE WARRANTY REGISTRATION FORM TO ACTIVATE THE WARRANTY.

Supplied with every engine is a complete copy of our warranty with an attached warranty registration form. This form can also be found here. Once filled out:
Then email a copy of each document within 45 days from the time of purchase to warranty@choateperformance.com. You should also retain a copy for your records as it may be required to assist with a warranty concern.
MODEL C STANDARD WARRANTY
1 Year / Unlimited Miles

THIS WARRANTY IS WITH THE PURCHASE OF THE INSTALLATION PACKAGE AND IS FOR THE ENGINE/WORKMANSHIP ONLY. NO LABOR PAYOUTS.
EXTENDED COMMERCIAL WARRANTIES ARE NOT AVAILABLE ON WORKHORSE, CASSQUATCH RACE SERIES, OR MODEL C ENGINES.
Remanufactured Heads — 6 Months
PARTS ONLY

Cylinder heads are warranted to be free from defects in material and workmanship. This warranty does not cover cylinder heads that are damaged due to improper installation, overheating, abuse, or accident.
Short Block Engines

Warranty coverage for Short Block engines does not include labor payout. We do not cover fluid leaks on any Short Block builds.
DAILY DRIVER WARRANTY
5 Year / 100,000 Miles

THIS WARRANTY IS NOT A FULL COVERAGE WARRANTY. PLEASE REVIEW YOUR WARRANTY CAREFULLY.
Labor rate for PREFERRED DEALER ONLY is a higher shop rate using Mitchell flat rate time.
WORKHORSE SERIES ENGINE
5 Year / 100,000 Miles

THIS WARRANTY IS NOT A FULL COVERAGE WARRANTY. PLEASE REVIEW YOUR WARRANTY CAREFULLY.
Labor rate for PREFERRED DEALER ONLY is a higher shop rate using Mitchell flat rate time.
YOUR CASSQUATCH RACE ENGINE
6 Months / 3,000 Miles
PARTS ONLY

THIS WARRANTY IS NOT A FULL COVERAGE WARRANTY. PLEASE REVIEW YOUR WARRANTY CAREFULLY.
CHOATE ENGINEERING PERFORMANCE COMMERCIAL WARRANTY
1 Year / 20,000 Miles

THIS WARRANTY IS NOT A FULL COVERAGE WARRANTY. PLEASE REVIEW YOUR WARRANTY CAREFULLY.
Labor rate for PREFERRED DEALER ONLY is a higher shop rate using Mitchell flat rate time.
CHOATE ENGINEERING PERFORMANCE EXTENDED COMMERCIAL WARRANTY
3 Year / 60,000 Miles

THIS WARRANTY IS NOT A FULL COVERAGE WARRANTY. PLEASE REVIEW YOUR WARRANTY CAREFULLY.
WARRANTY COVERAGE DETAILS
This warranty will cover remanufactured Short and Long-Block engines that are built by Choate Engineering Performance unless otherwise stated. From this page on, engines will be referred to as “unit(s)” and/or “engine(s)” unless otherwise stated. Fuel pump, injectors, and turbo warranties, and warranties on all accessories, are covered by the supplying manufacturer’s warranty.
FOR PREFERRED DEALERS ONLY: LABOR RATE IS SET AT A HIGHER RATE PER HOUR UP TO A MAXIMUM OF $2,500, NO EXCEPTIONS.
THE LIMITED WARRANTY WILL BE VOID AND WILL NOT APPLY TO DEFECTS OR FAILURES CAUSED BY THE FOLLOWING:
BUYER ALSO ACKNOWLEDGES THAT PROPER MAINTENANCE PROCEDURES ARE REQUIRED TO KEEP THE UNIT IN PROPER WORKING ORDER. CHOATE ENGINEERING PERFORMANCE WILL NOT ASSUME ANY RESPONSIBILITY FOR THE COST OF THIS ROUTINE MAINTENANCE.
Buyer acknowledges the following:
This warranty will not cover damages caused by the following for remanufactured engines:
Choate Engineering Performance limited warranty will end after the expiration of time or mileage from the date of the original invoice. Any repairs or replacements will not extend the warranty. The buyer shall be responsible for all defects thereafter, regardless of cause. Choate Engineering Performance limited warranty is in lieu of all other warranties expressed or implied.
The buyer agrees Choate Engineering Performance will not be responsible for:
TO QUALIFY FOR THE 5 YEAR / 100,000 MILE WARRANTY YOU MUST FOLLOW ALL INSTRUCTIONS AND REPLACE ALL PARTS SPECIFIED.
THIS WARRANTY IS TRANSFERABLE THROUGH PRIVATE SALE AND CHANGE OF OWNERSHIP ONLY ONCE IF CERTAIN CRITERIA ARE MET.
CHOATE ENGINEERING PERFORMANCE LIMITED WARRANTY FOR THE WORKHORSE AND CASSQUATCH SERIES ENGINES IS IN ADDITION TO ALL ITEMS LISTED IN THE STANDARD WARRANTY PACKAGE AND SUPERSEDES ALL MILEAGE REQUIREMENTS.
The Limited Warranty specifically does not cover the following:
FREIGHT / SHIPPING CHARGES

CHOATE ENGINEERING PERFORMANCE SHALL NOT BE RESPONSIBLE, NOR SHALL IT PAY ANY FREIGHT/SHIPPING CHARGES.
ADDITIONAL INFORMATION

As consideration for the above warranties, the buyer agrees they will take no action, statement, characterization, or implication regarding Choate Engineering Performance that may in any manner be interpreted as disparaging to Choate Engineering Performance or the reputation of Choate Engineering Performance. Any violation of this is a material breach, entitling Choate Engineering Performance to void any warranty.
