The Raptor piston is made from 4032 high silicon alloy. 4032 is a aluminum/copper alloy, (mix). It has low thermal expansion, and contraction properties.
This means you can have tighter piston to wall clearance, thus more power.

The crankshaft and connecting rod are made from
4340 chromoly steel forgings. 4340 is a type of stainless steel. It is very tough, and extremely wear resistant under very high temperature.

 

Good for you, DesertRaptor!! It's good to see someone with some technical knowledge clear up this rediculous subject. Most of us knew it all along. Aluminum? Gimme a break!

 

Where have you found this kind of info???????
It is really nice, but I never thought "anyone" could find the exact metal used for internal parts.
Cool.

but 4340 Chromoly...you must have some aluminium in there? Kidding.