lol its not easy, first of all when u put the head on u can "lock" the #1 piston in place and make sure it doesnt move until the head is installed and then obviously ur set up at tdc, next if the head is already on u can place a long extension, board, other object into the cylinder thru the spark plug hole (obviously make sure no debris fall into the cylinder) go to the highest point of the stroke, on the #1 cylinder and ur gonna be on either the intake stroke or exhaust stroke, so its a 50/50 from there, hopefully ur crankshaft pulley is marked so u can adjust the camshaft off of that mark. good luck putting it all back together.