I am wondering about two things that are being said. (1) The dimple is not very apparent on some cars. The dimple in the timing gears tend to be shallow and the timing pins tend to be blunt. In other words, when the pin drops into the dimple it can be oh so subtle. (2) looking down the spark plug hole, the piston is not right below the hole. It is at an angle to the front of the hole and towards the left side of the car. Use a bright flashlight. You can also verify that the timing gear is moving by observing the rotation of the distributor shaft. Like has been said; on a recently rebuilt engine, it seems unlikely that the pistons are not moving up and down as you crank. On the off chance that is the case, the next stop should be back to the rebuilder.
