I will be changing my timing belt in the next month. Instead of turning the cams and crank until all of the marks line up why can I not just put the new belt on in the same spot as the old one? The cam gears have a mark on them that the lines on the belt line up with. As long as the gears don't move after the old belt comes off and the new belt goes on with the lines on the cam gears marks what is the problem? This would eliminate turning the gears which is a pain unless you remove the spark plugs.
Thanks.

 

Well. I think that is exactly the issue - what happens if the gears turn? The idea is to line up everything first, by turning the crank, then remove the belt and install the new one and in so doing, make sure the cam gears are in the right position. If your crank isn't aligned to start, then the marks for the cam gears are worthless and you are likely to be off by a tooth or more. I think the FSM should walk you through the entire process in detail.

Andrew