As far as the not turning smoothly and springing back, that is the compression of the cylinders and seems perfectly normal. Now to the other part, you say there is more "clatter" than usual...if he timing belt were not installed properly, the enine would run terribly if at all. You may have the belt installed properly as far as timing goes but there may be a cover or guard not properly installed that is rubbing abainst a rotating part. I would go over the entire installation again before driving the car and make sure you don't have any left over parts and everyhing is were it came from. Also, you say there is more "clatter" but is the engine running roughly?

Jim