its my opinion that all the 6.3 156 engines, (with the exception of the SLS, they have a different intake, probibly tuned up a little and the exhaust too and maybe some Black Series which have to show some performance advantage or they wouldnt be the special high price exotic) are the same engines, just detuned BECAUSE they are anticipating the buyer and only giving as much as they 'need'.
A 'C' costs less and its a smaller car so they dont get as much HP, a CL costs alot and is heavy so they get more HP, a E is a sedan for families so they dont get as much HP, a SL is a sports car so they get more HP etc. You can simply look at Renntechs sales lit and see that every 156 6.3 says it reaches the same HP with their ecu tune. So it has to be the same engine. If you look at the new 5.5 turbo 157, its the same story. All different cars , even with the performance pkg have different HP but with their tune all get the same HP

 

There are a few versions of the C63 with hardware differences inside the motor, but the base C63 motor and the E, S, SL, etc. cars have nearly identical motors.

The P31 Development Package option on the C63 added the pistons, connecting rods, and crankshaft from the M159 motor in the SLS and the Edition 507 and Black Series go even further with internal upgrades. These different C63 versions come with unique ECU programming but all of them leave a good amount of power on the table for a competent tuner to unleash.

 

what are the differences? I think the SLS has a 82mm throttle body, along with different top plenum setup.

 

this is new to me! can you tell us further details please!

afaik, the m159 is identical to all m156 p31 versions except a different intake manifold and a dry sump. and afaik there are no more hardware upgrades on the m156 engines of the 507 and BS.


yes, but the sls intake manifold has no switching intake system that the c does have! so the sls manifold has more top end power but less on the low end. but the sls gearing is a lot shorter to compensate that (or the c gearing and especially the final drive gearset is veeeery long... for better mpg and to hold the performance gap to the sls).

the sls bs has different camshafts. the other camshafts are all the same afaik. or are there any more differences?