Hello,
The 230SL heads are based on the old M180 or M127 2.2 liter sedan engines. The mechanical injection required all the heads have wider chain galleries in the front compared to the carbureted sedan versions of the era. The 230 SL engine (M127) was a four main bearing engine. There were different heads for the 230SL during its production, but the differences were just minor improvements or upgrades and all the 230SL heads are interchangable. You can identify a 230SL head by its casting number. The 230SL head also holds its six injectors above its intake ports in the head. The M127 injected sedan heads did not accomodate any injectors since its mechanical injection used a two piston injection pump and all of its injectors were placed on the intake manifold. Also identify a 230 SL head by the 14mm valve adjusters (as opposed to the 17mm on a 280SL head).
The 250SL engine (M129) is basically a 230SL engine. The major diff. between the two blocks is that the M129 (250 series) uses a seven main crankshaft instead of the three mains in the 230series (thanks Scoot). The 250SL head is very similar to the 230SL head but does have some design improvements like larger valves. All the 230SL head and 250SL heads are interchangeable. Some 230SL owners upgrade there engines with the larger valve 250SL cylinder head. The fuel injected 250SE sedan engines of the time are (also M129) use the exact same heads as the SL. So the 250SE sedan head is a 250SL head or vice versa. Consequently the 250SE sedan engine can be a cylinder head donor for a 250SL or an upgrade head for a 230SL! These 250 series engines were all seven main bearing engines.
The M130 280 engines were very much different to the 230 and 250 engines even though the external size is identical. The cylinder diameters increased and the spacing between cylindes became dangerously close. It became so close that a cooling slot had to be machined in the narrow space between cylinders. There are two distinctly different 280 (M130) engines, the early version and the late version. The heads are not interchangable. Use the casting number on the head or the engine number to identify which version head. I refer to the early heads as "square" combustion chamber heads or the later as "oval" combustion chamber heads. Use my "Cylinder Head Chart" and the head casting number to quickly identify the two types. The fuel injected 280SE sedan engines of the era also used the same heads and they are the same on the 280SLs. However early and late heads and blocks DO NOT interchange!
There are some reports that the late 280 injected "oval" combustion chamber heads can be used on a 230 or 250 injected engine. I do not have any direct exprience on this matter.
Hope this helps,
Joe Alexander
Blacklick, Ohio
