The Mercedes-Benz M104 engine, a sophisticated inline-6 power plant, has seen variations throughout its production run. As enthusiasts and mechanics delve into these engines for repairs, modifications, or performance enhancements, questions arise about the subtle yet significant differences between various iterations. One area of particular interest is the cylinder head design, especially when comparing early and late models. Having recently disassembled 2.8, 3.0, and 3.2 M104 engines, several key distinctions in head design have become apparent, prompting an investigation into which design offers superior flow characteristics. This article will explore these differences, primarily focusing on the intake port design and related features of the Mercedes M104 cylinder head.
Let’s begin by visually examining the late model head. This particular head was sourced from a later W124 chassis vehicle. Notice the water port situated at the front of the head and the presence of a slider, rather than a roller, on the intake side of the chain drive.
In contrast, let’s observe the M104.980 head, extracted from a 1990 300CE-24. A prominent difference is immediately noticeable in the intake manifold mounting and the overall intake port architecture.
An intriguing observation is the valve visibility. In this earlier engine head, the valves appear less visible. This is attributed to the angle cut on the intake mounting flange, which is actually opposite to that found on the later M104 head. This design suggests that the early head was engineered to achieve a vertical intake mating surface when the engine is installed in the car at its characteristic 15-degree lean. Conversely, the later model head exhibits a more pronounced angle, resulting in a more radically upward angle for the EFI intake mount when installed.
Furthermore, the early model head incorporates a tensioner sprocket located directly beneath the intake cam. The water outlet is positioned directly on the side of the block, mirroring the M103 water outlet location, which likely explains its placement.
Comparing the two head designs side-by-side further emphasizes the visual and structural differences.
The central question that arises from these observations is: which of these Mercedes M104 cylinder head designs facilitates better flow? Leaving aside considerations of CIS versus EFI systems or engine displacement for the moment, the focus here is purely on head design. The intended application for this engine is performance-oriented, potentially in a lightweight chassis, making head flow characteristics a critical factor. Induction system considerations are also minimized as the engine will be managed by an aftermarket MS3 system. Therefore, understanding the inherent flow capabilities of each head design is paramount in optimizing engine performance. Further analysis and potentially flow bench testing would be required to definitively answer which Mercedes M104 head design ultimately provides superior airflow.
