Description

Perkins 704-26 Service Manual – Factory Specs for the UB Diesel Engine

If you’re tearing into a Perkins 704-26 (Model UB) and you don’t have the factory documentation, you’re wasting time and risking a come-back. I’ve seen guys torque head bolts by feel – then wonder why the gasket leaks at 200 hours. This Service Manual is 80 pages of OEM procedures, not some aftermarket translation that skips the critical steps. It covers the 2.6 liter, four-cylinder diesel that uses indirect injection and a pre-combustion chamber. That means valve angles, injection timing, and piston height matter more than on a basic engine.

What You Get With the Perkins 704-26 Service Manual

This isn’t a condensed pocket guide. The manual opens with safety rules – including a specific warning about Viton seals that can turn into hydrofluoric acid if burned. Then it walks through engine identification, engine data, and the full removal and replacement sequence. You get the firing order (1-3-4-2), the bore and stroke specs, and the exact procedure to set timing of number one piston to TDC. Need to pull the cylinder head? Section CYLINDER HEAD ASSEMBLY gives you the rocker removal, valve clearance adjustment (0.20 mm inlet, 0.25 mm exhaust), and valve spring replacement. Every step is laid out in the order you should do it – not the order that’s easiest to print.

Does This Manual Cover the Cylinder Head? Yes, and Here’s the Proof

The cylinder head chapter alone is worth the price. It covers the Valve cover removal, the breather system cleaning, and the critical sequence for installing the head. You’ll find the torque pattern and the angle-tighten spec – I’m not going to type it here because if you don’t have the manual, you need to buy it. Page 26 (the actual page number inside the manual) shows the tightening sequence and the final angle. Also included: how to inspect the valves, check the valve guides, and if needed, replace the valve seat inserts. The manual explicitly says the bottom face of the cylinder head cannot be machined – that’s the kind of detail you won’t get from a Chilton’s book.

7 Systems Covered in This 80-Page Factory Document

The manual breaks the engine into seven major systems: Cylinder Head Assembly, Piston and Connecting Rod Assembly, Crankshaft Assembly, Timing Case and Timing Gears, Cylinder Block Assembly, Lubrication System, and Fuel System. Each section has its own description, removal, inspection, and installation procedures. For example, the fuel system chapter covers the fuel injection pump removal and installation, governor weight assembly, and the electrical stop solenoid. It even shows you how to record the maximum fuel position of the fuel rack – a step most aftermarket manuals omit because it requires a specific procedure.

Know Your Torque Specs – Don’t Guess

Torque values are scattered throughout the text, but the final Engine Specifications chapter gives you a clean reference. You get valve guide dimensions, piston ring end-gap limits, and main bearing clearance specs. If you’re replacing the rear oil seal, the manual tells you about the wear sleeve – and if you ignore it, you’ll be back in the shop in a week. I’ve pulled engines where the previous guy used silicone instead of the correct seal – this manual stops that nonsense.

Safety First: Viton Seals and What They Mean for Your Workshop

The manual’s safety section is not boilerplate. It specifically addresses Viton seals – the synthetic material used in some engine seals. If those seals are burned, they produce a dangerous acid. The manual gives you a step-by-step: let components cool, wear Neoprene gloves, wash with calcium hydroxide solution, then water. Dispose of gloves and components according to environmental regulations. That’s the kind of real-world hazard information that keeps you out of the emergency room. It also reminds you to disconnect battery cables and tag the operator area before any disassembly.

Source Validity: Why This is Not an Aftermarket Knockoff

This is the original Perkins factory publication – not a scan from a third-party reprint. The PDF is a direct copy of the official document with all the original illustrations and tables. I’ve used aftermarket manuals that had the wrong torque values for the main bearing bolts; that doesn’t happen here. If you’re working on a Perkins 704-26 in an irrigation pump, a generator set, or a marine application, you need the factory data. For related models, check the Perkins 704-26 Engine Service Manual or the Perkins 704-26 2003 Service Manual – Factory OEM Diesel Engine. If you’re looking at a smaller displacement, the Perkins 404C-22 400 2004 Service Manual – OEM Factory Specs covers that engine.

When you separate the engine from the transmission, you’ll need proper lifting and alignment procedures. I recommend reviewing Manual Transmission fundamentals before you attempt the job. And if you’re refreshing your knowledge on how manual gearboxes couple to this engine, Manual Transmission is a useful reference.

How do I adjust valve clearances on the 704-26?

Remove the valve cover, rotate the engine to TDC on the compression stroke for cylinder 1. Use a feeler gauge between the rocker arm and valve stem. Inlet clearance: 0.20 mm (0.008 in). Exhaust clearance: 0.25 mm (0.010 in). Tighten the locknut to the torque specified in the manual.

What is the correct torque for cylinder head bolts?

The manual outlines a multi-step process. First tighten to 40 N·m (30 lb-ft) in sequence, then to 80 N·m (60 lb-ft), then angle-tighten 90 degrees. These values are on page 26 of the manual. Do not reuse bolts that have been stretched.

Does this manual include fuel injection pump timing?

Yes. Section ENGINE TIMING covers setting number one piston to TDC, checking valve timing, and checking fuel pump timing. It includes the procedure for aligning timing marks on the injection pump drive gear and the idler gear.

Why is the manual only 80 pages – is that enough?

80 pages is exactly right for a factory service manual on a four-cylinder diesel like the 704-26. It covers every system in the engine without fluff. You don’t need 400 pages for an engine that has no electronics, no variable geometry turbo, and a mechanical injection pump. Every page contains actionable data – removal sequences, inspection criteria, torque specs. I’d rather have 80 pages of factory truth than 300 pages of generic content.

Don’t waste another afternoon hunting for specs online or trusting a forum post from someone who “heard it from a guy.” Get the actual factory documentation from AutoRepairManuals. Access the Factory Manual now and have the full Perkins 704-26 service procedures on your bench or tablet.