The pistons are hitting the valves that are open. You have to remove the timing belt, then turn the camshafts until the timing marks are at the specified locations. Then you can turn the crankshaft to line its mark up. You'll need to remove the tensioner to get the belt off. What you have to watch is the camshafts will want to turn a little when the slack in the belt is taken up by the tensioner. That's why you have to double check for correct timing multiple times. Once everything appears to be correct, and you rotate the crank twice, any additional slack will get removed but the timing marks should still be in the correct relationship.
If either camshaft is off by one tooth, you'll feel the loss of power and you'll likely have a Check Engine light and a diagnostic fault code related to "cam and crank sync". Typically pistons hit and bend the valves when a cam sprocket is off by as little as three teeth.
If you can't turn a camshaft when the timing belt is off, carefully turn the crankshaft one way or the other so it's away from top dead center. It doesn't take much, but that will move all the pistons so none of them are up high enough to hit any valves. At that point you can turn the camshafts easily to get them to the correct positions, THEN you can bring the crank back to top dead center.
Wednesday, September 3rd, 2014 AT 2:00 PM