I'm not real sure what Kye is looking at (Sorry Kye) but I defiantly don't see any model parts on the HG Noble.It all looks to be model 2 parts to me.
I think you are comparing the HG Noble cylinder to the HG Palmer cylinder and yes they are different and the HG Palmer engine was more based of a Model 3 engine.Which is a completely different casting from the Model 1 & model 2.

Here for a good time,not a long time.