I am replacing a head gasket on a D15B7 engine. I aligned the arrow on the oil casing with the mark on the crank gear, but the 'up' mark on the cam gear is just a little before 12 o'clock and the cam marks are not exactly even with the head. The crank mark and the arrow are aligned, but maybe not exact as the belt is kind of in the way of the arrow. Shouldn't the 'up' mark be right at 12 o'clock if the crank and arrow are aligned? Which is more important to be aligned before I take off the head?