Waterboxer Big Bore Barrel And Piston Kit - 95.5mm - 2100cc (Converts To 2178cc)

This big bore cast barrel and piston kit is designed to increase engine capacity on 2.1 Waterboxer (WBX) engines from 2100cc to 2178cc, delivering improved torque and stronger overall drivability while retaining factory-style fitment. It is a bolt-on upgrade, requiring no machining, making it ideal for engine rebuilds or performance-focused refreshes.

The kit uses carefully matched pistons and cast barrels engineered to work with the standard Waterboxer crankcase and cylinder heads, allowing a capacity increase without altering the engine’s external geometry.

What this kit does (and why it matters)

The 2.1 Waterboxer is well suited to a mild displacement increase, particularly in heavier Type 25 / T3 buses. This big bore kit:

• Increases displacement from 2100cc to 2178cc

• Improves low-end and mid-range torque

• Enhances drivability under load and on inclines

• Retains standard engine architecture and reliability

Because the upgrade does not require machining, it keeps rebuild costs under control while delivering a noticeable performance gain.

How it works

The kit uses big bore pistons and cast barrels matched to the standard 74mm crankshaft stroke used in 2.1 WBX engines. By increasing bore size while maintaining original external dimensions, the pistons sweep a greater volume during each stroke, increasing total engine capacity and torque output.

The piston design, compression height, and dish volume are specified to maintain suitable compression characteristics for Waterboxer engines when assembled correctly.

Kit contents

Supplied as a complete set for one engine:

• 4 x big bore pistons

• 4 x cast cylinder barrels

• 4 x gudgeon (wrist) pins

• Circlips / piston clips included

Measurements & specifications

• Capacity increase: 2100cc → 2178cc

• Stroke: 74mm

• Piston type: Cast

• Compression height: 36.8mm

• Piston dish: 46cc

• Fitment type: Bolt-on (no machining required – 95.5mm)

• Quantity: Set of 4 pistons and barrels

Engine compatibility

Suitable for 2100cc Waterboxer engines fitted to:

• VW Type 25 / T3 buses (1983–1992)

Helpful fitting notes

• This kit covers all four cylinders, regardless of side

• Always check piston orientation and ring end gaps before final assembly.

• Cylinder heads must be flat and in good condition to ensure correct sealing.

• Follow the factory torque sequence and tightening stages when refitting cylinder heads.

• A careful cooling system bleed after installation is essential on Waterboxer engines.

Parts you may also need (recommended)

For best results and long-term reliability, consider replacing or inspecting:

• Cylinder head gasket / sealing kits

• Barrel liner seals (top and bottom)

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

• Full engine gasket set if doing a complete rebuild

• Fresh oil and coolant after assembly