OM606 Stroker Build Guide – 2.3 2.9 and 3.5 Litre Conversion Explained

OM606 stroker build fundamentals are simpler than most people think but require knowledge of which parts work together across the Mercedes diesel engine family. Today we cover the basics of building 2.3, 2.9 and 3.5 litre stroker engines from OM604, OM605 and OM606 bases.

The Three Stroker Configurations

All three four valve engines can be built as strokers sharing identical stroke and bore specifications:

• OM604 base → 2.3 litre stroker
• OM605 base → 2.9 litre stroker
• OM606 base → 3.5 litre stroker

The cranks come from two valve engines in the same Mercedes family. The stroke sources are:

• 2.3 litre stroke: OM601 2.3 litre or OM601 2.2 litre US specification
• 2.9 litre stroke: OM602 2.9 litre direct injection E-class 290 TDT
• 3.5 litre stroke: OM603 from S-class and G-wagon applications

All stroker configurations use 89mm bore pistons. The two valve engines with the correct strokes already use 89mm bore so the piston specification is consistent across all three build types.

What Cannot Be Done

A common question is whether a two valve block can be used with a four valve head to build a stroker. The answer is no.

Pre-chamber placement is completely different between two valve and four valve engines. Everything is in different positions. You cannot combine a two valve bottom end with a four valve head in any straightforward way. Some builders have created extremely complex hacks to make this work but the result is always far more complicated than simply using four valve components throughout.

Build your stroker with four valve parts throughout. Use the two valve crank for the stroke but combine it with four valve block, pistons, rods and head. This is how it works as close to factory intent as possible.

The Parts Challenge

Getting all the correct parts to work together requires knowledge of the engine family across multiple models. This is where experience matters enormously. Someone who has torn apart and rebuilt many different Mercedes diesel engines knows instinctively which components are interchangeable and which require modification.

The rod selection for stroker builds has one primary source that fits correctly without major modification. Identifying this requires doing the math on stroke, con rod length, compression height and deck clearance – all straightforward calculations if you know the engine family dimensions.

Oil squirters from two valve engines may or may not be compatible with four valve blocks. This has not been definitively tested and is an area where caution and verification are required before assuming interchangeability.

Real World Build Experience

One particularly complex stroker build involved boring the wrist pin holes in four valve pistons from 26mm to 28mm and machining new circlip grooves. The 28mm wrist pin from the donor application turned out to be wider than the 26mm version requiring the wrist pin to be shortened on a lathe. The machining process produced significant heat and smoke but achieved the goal.

The deck height of the assembled engine came out one millimetre too tall requiring the block deck to be machined down one millimetre. It worked but represented an enormous amount of additional labour compared to using correct specification parts from the start.

The lesson – use the correct parts and the build comes together logically. Substitute parts and every substitution creates cascading problems that require creative solutions.

Stroker Character and Camshaft Selection

A 3.5 litre OM606 stroker does not behave like a standard 3.0 litre OM606. The additional displacement and longer stroke create a noticeably more torquey character. These engines are particularly well suited to off-road applications and builds where low to mid range torque matters more than ultimate top end power.

The stroker can still rev freely – a 3.5 litre OM606 pulls to 7500 RPM and responds with the same enthusiasm as a standard engine. But the torque character at lower RPM is meaningfully stronger.

For race stroker builds camshaft selection becomes important. More displacement means more exhaust gas volume requiring faster exhaust valve opening to clear the cylinder effectively. On race stroker builds an NA intake camshaft combined with a Stage 1 exhaust camshaft has produced excellent results – the exhaust cam moves gases out faster while the intake cam fills the larger cylinder volume effectively.

For street stroker builds standard camshafts work very well. The engine is gentler, torquier and very pleasant to drive in daily use.

Why Build a Stroker

A 3.5 litre OM606 is genuinely rare. Approximately twelve to fifteen exist globally. Running one makes you part of an extremely small group of builders who have pushed this engine family beyond its standard displacement limits.

The performance advantage is real – equivalent to adding a seventh cylinder to a six cylinder engine in terms of displacement increase over standard. Combined with the correct turbo and injection pump setup these engines produce extraordinary results.

Summary

• OM606 stroker build uses two valve cranks combined with four valve engine components
• Three configurations: 2.3L OM604, 2.9L OM605, 3.5L OM606
• Crank sources: OM601 for 2.3L, OM602 290TDT for 2.9L, OM603 for 3.5L
• All stroker builds require 89mm bore pistons
• Two valve blocks cannot be combined with four valve heads
• Rod selection requires calculation and has limited correct options
• Deck height verification and possible machining is required
• Stroker character is torquier and more aggressive especially off-road
• Race builds benefit from NA intake cam combined with Stage 1 exhaust cam
• A 3.5 litre OM606 is one of approximately 12-15 in existence worldwide

Order your stroker engine today. Love what I do. Bye!