Because of the longer stroke it's possible for the big end of the connecting rod to hit the cam as it passes by. Usually stock rods with regular nut and bolt type rod bolts. #'s 1, 2, 5, and 6 are the most likely to hit. Some people think that small base circle cams will fix this but not always. It usually depends on what rods you're using. Clearanced cap screw type rods are usually your best bet for having enough clearance out of the box.
BSE Racing Engines