Remove your rocker arm on say the #1 cylinder. Take a sharpie permanent marker and color the valve tip. Replace your rocker arms and rotate engine over by hand 2 or 3 times. Remove rockers again and make sure you have a clean even line in the center of valve stem if not p.rods need to be altered or rockers shimmed.
You also want to make sure the rocker is riding on the center of the valve tip. You could use a adjustable pushrod to determine if you have the correct length.