Quote:
Originally Posted by Gilles
Jake: if you have a choice (similar cost) which route would you choose, BTW my car (CS '07) has a 3.4 M97.21
a) My 3.4 with 3.8 LN Nickies and forged rods. Q: Is the stock 3.4 crank strong enough? Would the cylinder walls be too thin & risk overheating?
b) A 3.8 from a Carrera S with LN Nickies and forged rods? But have to deal with the DME change and key programming etc.,
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Loaded question, with way too many potential variables for a general answer.
The crankcase for the Carrera S is not special, its the same as your M97.21 in most every way. It has larger diameter cylinders from the factory, but we never care about that.
Now, if you use the Carrera S engine, you'll have front console issues, as the water necks and routing are different than the M97.21, AND you'll have to weld, drill and tap to fit your unit onto the case. You won't learn this until the engine is almost done with assembly.
If running Nickies, we can go clear to 104mm without overheating concerns, unless you misconfigure the engine combination, and CAUSE the engine to generate more heat. Lots of people are doing that with stock bore sizes these days, or going to some funky iron cylinder that causes problems, too.
You need to educate yourself separate from whats online, most of it is plain wrong, or being distributed by some clown that doesn't even change his own oil.
You have one chance to do this right. Learning curves are 90 degrees and margins of error are near zero. This is why I offer classes.
I always stick with the M# designation that the vehicle came with, unless its a crazy project with no budget or time constraints.