Kyle' S Corner (FYI) the Mercedes 300 SL Gullwing: Fabulous but Its Engine Had a Humble Beginning

If you go back through
automotive history, you
will find many instances
in which great cars have
come from humble
beginnings, beginnings
in which automotive
people had to work hard
or else ... There was none
of today's if it works, we
make a lot of money and
if it does not, the
government and taxpayers
will ...

Automotive enthusiast know that the Mercedes 300 SL Gullwing is a great
car and a collector item. However, its engine actually started out from very
humble beginnings. The 1954-57 300 SL Gullwing and the 1957-63 300 SL
Roadster were powered by the Mercedes M198 three-liter straight six-cylinder
engine equipped with direct mechanical fuel injection

The M198 engine was very much ahead of its time. Its direct fuel injection
(many automakers are introducing direct fuel injection today) was derived
from Mercedes' V12 aro engines that powered Germany's Me 109 fighter
planes Additionally, the engine had dry-sump lubrication (used in racing
units) and was canted 50 degrees to fit under the Gullwing's sleek hood line.

Of the engine Martin Cushway (an expert on the 300 SL and owner of both a
Gullwing and a Roadster) states in Thoroughbreds & Classic Cars, "'Despite
its advanced design, the M198 was not the result of lavish budgets and unlimited
resources. Instead, it evolved in the 50s when the motto in austerity-hit Britain
was still 'make do and mend.'"

Rule changes in 1950 rendered Mercedes' three-liter supercharged engine
out for the W154/163 Grand Prix cars. Therefore, Mercedes racing director
Alfred Neubauer made plans to adopt the M186 2996cc sedan car engine as the
foundation for Mercedes' sports car racing in 1952-53. His goal was 200 hp and
this was a challenge as he had to work with a cerebrated production car engine.

Development for the engine started in the autumn of 1951. The first version of
the engine had two Solex carburetors and made 115 hp. The second version
with three Solex carburetors yielded 150 hp and a third version with a raised
compression ratio produced 172 hp. In the spring of 1952, the Mercedes board
held a press conference to announce its intention to enter sports car racing
internationally.

Even though the board stood behind the M194 cerebrated sports car engine,
Neubauer still had to go to the existing parts bin for the engine's development.
However, he was given a new sports car to put the engine in - the 300 SL
Gullwing! Development continued on the carbureted engine but finally there
was a budget increase. As the Gullwing's spaceframe was completed, the focus
for development moved to the engine. In the spring and summer of 1953,
Mercedes began talks with Bosch on fuel delivery for the engine.

By fall, four fuel injected engines had been built that produced 215 - 225 hp.
A bit later, an engine equipped with a race profile camshaft punched out 240 hp.
As the power of the engine was achieved, the focus shifted to engine reliability
and durability testing at Hockenheim and Solitude west of Stuttgart. After four
weeks of continuous testing, one of the engines obtained an equivalent of 215,000
miles before it was disassembled to inspect for engine wear. The same engine was
used in test rigs and in cars until 1956 and thus amassed more than 500,000 miles.

Regarding testing of the engine, Mercedes used 'drehfest' which translates to
'turning tight.' By this the engineers meant that if an engine is well designed,
and it is provided with the correct amount of fuel, oil and spark, it will produce
maximum power almost forever.

So what is the foundation for the 300 SL Gullwing engine? In Thoroughbred &
Classic Cars, Cushway says, "It was of a typically high basic specification with
seven main bearings and a duplex roller timing chain. The valve gear comprised
a single overhead camshaft operating both inlet and exhaust valves via rockers."

The carbureted engine started out with a cast iron block and an alloy cylinder
head. Rather than being mounted in the head, the spark plugs were located
horizontally in the top of the block. A bit later, the fuel injectors were placed
in the spark plug holes and the spark plugs were relocated into the head as is the
conventional practice. Other features of the engine included the piston crowns
(on the injector side) were machined off at an angle creating a neat combustion
chamber. As the cylinder block was usually machined at a 20 degree angle, larger
inlet and exhaust valves were able to be installed.

The M198 engine was in production until 1963 and then the 300 SL Gullwing
was replaced by the 230 SL that was powered by a 2.3-liter M127 II straight
six-cylinder engine. By that time, the M198 engine had become a legend thanks
to Mercedes design engineering and rigorous testing. Thus, many fine examples
of the Mercedes 300 SL still provide a thrilling driving experience today. And
from its humble beginning, the engine provides a growl that few can match!

Kyle Busch is the author of "Drive the Best for the Price..." He
welcomes your comments or car questions at his auto web site:
www.DriveTheBestBook.com.