Difference between Quad 4 and the 2.4L

What is the difference:

Quad 4 dohc 16 valves vs. 2.4L Twin Cam

They are actually the same, its just that quad 4 usually refers the the 2.3L engines. 1995 was the last year they were put into the grand am.

The 2.4L DOHC is the latest version of the original Quad 4 2.3L. It's an Oldsmobile engine. Aside from improvements/changes since it's intro in '87, they are the "same" motor. Olds will no longer be making the Quad 4 according to legend (and the fact that Olds no longer exists.).