20v 4 cyl engine

I was just messing about in the sandbox making a 2L 4 cyl turbo engine, and I noticed that the cam belt isnt animated on the engine, if I swap it for a 4 valve head the belt goes round but it just stays still on the 20v.
A tycoon game made for people who live and breathe cars.
http://phpbb3.automationgame.com/