Waterboxer Big Bore Barrel And Piston Kit - 95.5mm - 1900cc (Converts To 1977cc)

This big bore cast barrel and piston kit is designed to increase engine capacity on 1.9 Waterboxer (WBX) engines from the original 1900cc to 1977cc, delivering a noticeable improvement in torque and drivability without compromising reliability. It is a true bolt-on upgrade, requiring no machining, making it an ideal upgrade during an engine rebuild or top-end refresh.

Using the same outer barrel dimensions as standard 1.9 WBX cylinders but with thinner barrel walls, this kit allows for a larger piston diameter while remaining fully compatible with standard crankcases and cylinder heads.

What this kit does (and why it matters)

Increasing displacement improves low-end and mid-range torque—exactly where a T3 / Type 25 benefits most. This big bore kit:

• Increases capacity from 1900cc to 1977cc

• Improves pulling power, especially in heavier buses

• Enhances drivability without stressing the engine

• Maintains factory-style fitment and geometry

Because the Waterboxer is often worked hard in real-world driving, the extra displacement helps the engine feel less strained, particularly on hills or when fully loaded.

How it works

The kit uses 95mm pistons matched to specially cast barrels that retain the original outer diameters:

• Same outer diameter as standard barrels

• Thinner cylinder walls allow the larger piston

• Works with the standard 69mm crankshaft stroke

• No case or head machining required

Each piston converts combustion pressure into rotational force via the connecting rods, while the piston rings seal combustion gases, control oil, and transfer heat to the barrel—ensuring stable operating temperatures and long service life when assembled correctly.

Kit contents

Supplied as a complete set for one engine:

• 4 x 95mm pistons

• 4 x cast cylinder barrels

• 4 x gudgeon (wrist) pins

• Circlips / piston clips included

Technical specifications

• Capacity increase: 1900cc → 1977cc

• Bore: 95mm

• Stroke: 69mm

• Upper barrel diameter: 107mm

• Lower barrel diameter: 100mm

• Quantity: Set of 4 pistons and barrels

• Fitment type: Bolt-on, no machining required

Engine compatibility

Fits 1.9 Waterboxer engines with the following engine codes:

• DF – 1.9

• DG – 1.9

• DH – 1.9

• GW – 1.9

• SP – 1.9

Applications:

• VW Type 25 / T3 (1983–1992)

Helpful fitting notes

• Covers all four cylinders.

• Pistons must be installed in the correct orientation—check markings carefully.

• Always check ring end gaps before final assembly.

• Cylinder heads should be flat and in good condition to ensure proper sealing.

• Correct torque sequence and staged tightening of the heads is essential.

Parts you may also need (strongly recommended)

When fitting a big bore kit, it’s good practice to replace or inspect:

• Cylinder head gasket / sealing kits

• Barrel liner seals (top and bottom)

• Piston rings (if not pre-fitted or if upgrading)

• Main and big-end bearings (depending on mileage)

• Full engine gasket set for rebuilds

• Fresh oil and coolant, followed by correct cooling system bleeding