Description

Sisudiesel 320, 420, 620, 634 2002 Workshop Manual

Let me be clear: the Sisudiesel 320, 420, 620, 634 2002 Workshop Manual is what you need if you’re tearing into any of these engines. I’ve seen too many guys try to rebuild a 620 with a photocopied spec sheet from a forum and end up with a cracked cylinder head. This 114-page OEM manual gives you the factory sequence for every major assembly. Not aftermarket garbage. Real numbers. Real procedures.

Engine Specifications and Technical Data (page 0-3)

Before you wrench on anything, you need the baseline numbers. The ENGINE SPECIFICATIONS section on page 0-3 lists bore, stroke, firing order, and compression ratios for all four models. The 320 and 420 share a common block design, but the 620 and 634 have different crankshaft throws. This manual lays out the differences so you don’t order the wrong piston set. The technical data section also includes cylinder liner protrusion, main bearing journal diameters, and camshaft lift values. Page 0-3 is your starting point before you pull the head.

Tightening Torques: Where Most People Get It Wrong

The TIGHTENING TORQUES section in TECHNICAL DATA (page 0-6) is where the rubber meets the road. Cylinder head bolts, main bearing caps, connecting rod nuts – all specified in ft-lbs. If you’re used to generic values, you’ll be off. For the 634, the head bolt torque sequence is critical because of the larger bore. Skip the sequence and you’ll warp the deck. The manual shows the exact pattern and torque steps. I’ve torqued enough heads to know that the difference between 85 and 95 ft-lbs on a cylinder block can cost you a gasket failure. This manual gets it right.

Cylinder Head and Valve Mechanism: Overhaul Procedure

Chapters 3 and 4 cover cylinder head removal, valve lapping, and installing new valve guides. The manual lists special tools needed – like valve spring compressor Sisu tool number [DATA NEEDED] – and gives the stem-to-guide clearance specs. I’ve done this job on a 420. Without the factory clearance numbers, you’ll either get valve sticking or oil burning. The valve mechanism chapter also covers rocker arm shaft assembly, tappet clearance adjustment, and camshaft timing marks. If you’re setting the valve lash on a 634, the cold and hot settings are given. The crankshaft section (chapter 5) pairs with this, showing the bearing clearance checks using Plastigage. Combine these two chapters and you can do a top-end rebuild on any Sisudiesel engine in that range.

Cooling System and Fuel System: Factory Diagnostics

Chapter 11 covers the cooling system – thermostat opening temp, water pump inspection, and coolant capacity. Chapter 13 and 14 cover the fuel system: injection pump timing, injector removal, and the fuel system equipment feeding table. If you’re chasing a no-start on a 620, the fuel system section has the bleeding procedure and pump timing marks. Don’t guess – use the manual’s alignment procedure. The cooling chapter also includes belt tension specs and hose routing diagrams. For marine applications, the optional equipment chapter (16) adds raw-water pump service data. This is the kind of detail you won’t find in a aftermarket reprint.

Sisudiesel 320, 420, 620, 634 2002 Workshop Manual: What You Actually Get

This is the genuine 2002 workshop manual, 114 pages, covering all four engine models. Inside you’ll find safety instructions, a special tools list, construction details, and 16 chapters from cylinder block to optional equipment. Each chapter includes disassembly, inspection, and assembly steps with tolerance tables. The manual uses imperial units where applicable. If you need the exact procedure for removing the counterbalance assembly (chapter 7) or timing gear alignment (chapter 9), it’s all here. No generic diagrams – real factory drawings with part callouts.

Why OEM Documentation Beats Aftermarket Copies

I’ve wasted hours on aftermarket manuals that had the wrong calibration data for injection pumps. This is an original Sisudiesel publication. The torque values come from the same engineering department that designed the engine. If you’re rebuilding a 634 for a generator set or a 320 for a tractor, this is the only source you should trust. The safety instructions alone (page 0-2) are worth the price – they warn you about high-pressure injection hazards and proper lifting points for the engine assembly. Don’t risk your shop’s reputation on a photocopy.

Does this manual cover the 634 model?

It covers all four: 320, 420, 620, and 634.

What torque specs are included?

Cylinder head bolts, main bearings, connecting rods, flywheel, and many more – all listed in the TIGHTENING TORQUES section with tightening sequences.

Is this a PDF or a printed book?

Digital access. You get the full 114-page PDF, searchable, printable. Immediate access after purchase.

Can I use this for a 620 engine in a boat?

The manual covers all applications of the Sisudiesel 620 engine – marine, industrial, generator. The fuel system and cooling sections include specific data for different installations. If your boat’s 620 has a heat exchanger, the cooling system chapter covers raw water and closed-circuit setups. You’ll need to identify your engine serial number to confirm the exact variant, but the core rebuild procedures are identical. The optional equipment chapter also includes data for marine flanges and couplings.

Related manuals you might need: SisuDiesel Fortius Series Engines Workshop Manual, SisuDiesel Citius Series 44 49 66 74 84 Workshop Manual, SisuDiesel 645 Engine Workshop Manual 01.02. For transmission work, see Manual Transmission and Manual Transmission for clutch alignment and gearbox mating procedures.

If you’re serious about doing the job right the first time, access the Factory Manual. Every torque value, every clearance spec, every step is laid out by the people who built the engine. Stop relying on forum guesses. Access the Factory Manual from AutoRepairManuals and get back to wrenching with real data.