Hello Mark,
The crankshaft on the M127 230-SL engine's crankshaft is counterbalanced to the front vibration dampner and the flywheel. In other words, these four main bearing crankshafts are out of balance by themselves. To achieve balance, an out of balance vibration dampner and a out of balance flywheel are used. It is just like adding wheel weights to an out of balanced wheel. So the vibration dampner and flywheel of the M127 engine have masses added (counter weights).
In comparison the seven main bearing crankshaft of the 250-SL and 280-SL are balanced in themselves. A balanced vibration dampner and a balanced flywheel are used with these crankshafts.
The automatic flywheels and standard flywheels in your 230-SL engines can be swapped as long as they are both 230-SL engines. The 250-SL, 280-SL standard and automatic flywheels can also be swapped in their respective engine series.
In all cases a transmission shaft centering bearing is installed in the crankshaft at the factory for all standard transmission cars. This most be removed or added depending on which tranmissiion you use.
The flywheel to crankshaft bolts are different lengths for standard or automatics also.
Your spare standard transmission engine will work fine in your automatic 230-SL. You will need to remove the flywheel and extract the centering bearing out of the crankshaft. Your original automatic flywheel can be bolted up to your spare engine using the flywheel/crankshaft bolts from the automatic.
Before the change over, you can take the original counterbalaced automatic flywheel and the counterbalanced standard flywheel to a performance shop and have your automatic flywheel exactly counter balanced the same as the standard flywheel.
Joe Alexander
Blacklick, Ohio
