Need a little more info... so you have the 2.0 heads and the new 2.5 block? With the new cams I am assuming you adjusted the valves or at least checked the valve clearances? Are you 100% sure the timing belt is installed properly? What happens when you try to turn the car over? It just cranks? Do you hear the fuel pump turning on when you turn the key? Are there any codes in the ECU?