Quote Originally Posted by IXLR8 View Post
I think you missed my point. An aluminum motor radiates heat better than a cast iron motor. It's like adding more cooling capacity, and will usually allow a tiny bit more timing and compression.
I know exactly what you are saying, but the cooling system is what determines operating temperature, not heat radiation from the block. It might cool slightly faster after shut down, but while the engine is running it won't affect it. If both engines have the same thermostat and cooling system, they will both run at the same temp.