360 driveability problem

checked the distributor today.all springs hooked up.everything seems to be working there. i turned the motor past tdc.then turned back to tdc.had the cap removed and found the engine will turn approximately 8 deg.before the rotor moves.so i figured timing chain worn.tore it apart.has double roller.bottom sprocket has 3 key ways.it is set in the 0.has one with an A and one with a R.is it a possibility it should have been set on one of these instead of the 0??