yeah if the timing is way off there will be valve to piston contact, but if it is off little bit it will miss sort of like a sputter and idle bad in some cases like it wants to stall and it will run like crap. firing order is the position of where the wires coming from the plug connects to the distributor cap. for example #1 spark plug wire may connect to the upper rear connect point on the dizzy #2 might connect to the lower rear and so on. mostly on hondas its either clockswise or counterclockwise, example 1,2,3,4 facing the front of the engine or 4,3,2,1 facing the rear of the engine. your best bet is to find someone with a si and look to see how thier firing order goes, also you might want to use the dizzy that came with the head.