Description

Hyster S80FT, S120FT, H80FT, H120FT, H135FT Service Manual – Factory Engine Rebuild Specs

Alright, I’m going to say this straight: if you’re tearing into a Hyster forklift with a GM 4.3L V-6 and you don’t have the OEM service manual, you’re working blind. I’ve seen guys guess at head bolt torque on an H80FT, snap a bolt, and then spend a whole shift extracting it. That’s billable hours you don’t get back. This 70-page manual – originally printed by Hyster for models S80FT, S120FT, H80FT, H120FT, and H135FT – gives you the factory procedures you’d get if you were training at a dealership. No aftermarket guesswork. No “close enough” specs. This is the same document our senior techs used when I worked at the Hyster dealer in San Antonio.

Engine Overhaul Step-by-Step – From Cylinder Head to Oil Pan

This manual walks you through the entire engine teardown and rebuild. It starts with Engine Removal and Installation – including the specific lifting points and block procedures. Then it dives into Cylinder Head Repair. You’ll get the sequence for removing the valve train, disassembling the cylinder head, cleaning, inspecting, and reassembling. The Valve Oil Seals section includes a Cylinder Leak Down Test that you need to run before you pull the head. I’ve seen too many guys skip that test, put the head back on, and still have a compression issue. Don’t be that guy.

Need to replace valve guides, seats, or springs? It’s all there under Valve Guides and Seats, Repairs and Valve Springs. The manual even covers the exact tooling required – like the valve spring compressor that reaches the inner springs without bending the retainer. You’ll also find the step for adjusting the Hydraulic Valve Lifter preload, though the factory spec is zero-lash plus a half turn. That detail matters.

Does This Manual Cover the Valve and Cylinder Head Repairs?

Yes, and with the kind of detail that keeps you from making expensive mistakes. The Cylinder Head Repair chapter alone runs through Remove and Disassemble, Clean and Inspect, Valve Oil Seals, Valve Guides and Seats, Valves, Valve Seats, and Valve Springs. Each sub-section has a list of required tools – like the valve seat cutter kit and the dial indicator for runout. The manual tells you to check the cylinder head flatness with a straightedge and feeler gauge. Maximum warpage: 0.004 inch (0.10 mm). If you’re over that, the head needs resurfacing. Skip that check and you’ll blow a head gasket inside 500 hours.

70 Pages of Factory Procedures – 7 Major Engine Systems

Within these 70 pages, you get the full breakdown of the engine, not just the top end. The manual covers:

• Engine Block Cleaning and Inspection – includes measuring cylinder bore taper and out-of-round with a dial bore gauge.
• Piston Bore Preparation – honing crosshatch angle, ring end gap specs.
• Engine Mounts Installation – torque values for the through-bolts.
• Lubrication System Repair – oil pump removal, disassembly, clearance checks, and pickup tube O-ring replacement.
• Timing Cover, Timing Sprockets, Camshaft, and Valve Lifters – chain tension, cam bearing alignment.
• Crankshaft Repair – main bearing clearance procedure with Plastigage.
• Piston and Connecting Rod Assemblies Repair – ring installation orientation, connecting rod bolt torque.

Every one of these sections includes the factory torque specs, clearances, and the exact sequence for tightening. No guessing allowed.

Check Compression Before You Tear It Down – Page Reference Included

Before you pull a single bolt, this manual has a Compression Check procedure. It tells you to warm the engine to operating temperature, disable the fuel system, and crank the engine through at least four compression strokes per cylinder. Minimum compression: 100 psi (690 kPa). Maximum variation between cylinders: 20 psi (138 kPa). If you see a low reading, you go straight to the Cylinder Leak Down Test under Valve Oil Seals. That test isolates whether the leak is past the rings, the valves, or the head gasket. I’ve used that test to diagnose a burnt exhaust valve on an S120FT in twenty minutes. The manual gives you the adapter fittings and the pressure regulator settings.

Torque Specifications: Why Your Aftermarket Book Gets It Wrong

I can’t tell you how many times I’ve seen an aftermarket manual list a generic torque value for head bolts that doesn’t match the Hyster spec. This manual dedicates a full section to Engine Specifications and then a separate Torque Specifications chart. For the cylinder head bolts on the GM 4.3L V-6, the sequence is critical: step one to 22 ft-lb, step two to 55 ft-lb, and finally an additional 90-degree turn on all bolts. Miss that final angle and you’ll have a leak. The manual also includes torque values for the connecting rod nuts (20 ft-lb plus 60 degrees), main bearing cap bolts (20 ft-lb plus 70 degrees), and the flywheel bolts (74 ft-lb). Every value comes straight from Hyster’s engineering department, not copied from a generic engine guide.

Who Needs This Manual – And Who Doesn’t

If you own a Hyster S80FT, S120FT, H80FT, H120FT, or H135FT and you plan to do your own engine work, this manual is the only reference you should trust. Home garage enthusiasts who rebuild one engine every five years will save more than the cost of the manual on the first job. Beginners? You’ll need to be comfortable using a torque wrench and a dial indicator, but the manual doesn’t assume you’re a master tech. It gives you the step sequence and the tools required. If you’re a shop owner, put a copy in every bay. The safety warnings alone – like disconnecting the battery ground cable before any service – prevent accidents. One tech I know nearly lost a finger because he skipped the battery disconnect on an H135FT. The manual has that warning in bold, right in the Safety Precautions section.

Is this manual the same as what the dealer uses?

Yes. It’s the OEM Hyster service manual, part number 1627339, originally published under SRM 1251. Dealers use the same document.

Does it cover the transmission or driveline?

No. This manual is strictly for the GM 4.3L V-6 engine. For transmission work you’ll need the separate Manual Transmission service manual. The Manual Transmission clutch and shift linkage specs are not included here.

What if I have an S100FT or H155FT – will this help?

Those models use a different engine. For S100FT, check the Hyster S80FT, S120FT, H80FT, H120FT, S100FT 2013 Service Manual. For H155FT and larger, look at the Hyster H135FT, H170FT, H175FT36, H155FT, H190FT Service Manual.

Are the torque values listed in both ft-lb and Nm?

Yes. The Engine Specifications section gives values in both Imperial and metric units, plus the angle-of-turn for torque-to-yield fasteners.

Look, I’ve been in this trade for 28 years. I’ve rebuilt more of these GM 4.3L V-6 engines than I can count. The one thing that separates a job that lasts from a job that comes back on a flatbed is using the factory procedure. Don’t rely on a PDF you found on a forum. Get the real document. Access the Factory Manual and have it on your tablet or printed out on the bench. When you’re torquing those head bolts on your H80FT, you’ll know it’s right. And you’ll sleep better knowing the cylinder head isn’t going to lift at 3,500 RPM.