My fellow Zilvians i need ur HELP!!!!!!

[NISMO NES]

Ok I recently did my swap on my S13 with an SR Blacktop. I took out the motor from my old hatch and swithced it over onto my other S13 hatch (motor been out and not running for 3 moths). I put some Royal Purple 10W/40 wen i cranked it over it made this type of sound TATATATATA at normal steady rpms wich is 900 now my motor is advanced by 38 degrees now wen i took it out for a liitle test drive my motor was running real rough and the sound on the mototr just got real loud so i was thinking now that sound turned into a clanking sound. BUt wen i stopped, it went back into that normal tatata sound. Wat i did today was took off the valve cover and spinned the cams manualy clock wise and notice at one point that wen turning, it turned real smooth and then it got hard to turn and wen i turned it made a clack sound i did not notice wat it was but i repeated this 3 times and it still did the same CLACK at one point of the turn. Wat do u guys think this type of situation is? or, is that clanking noise normal wen i turn the cam manualy? thanks i greatly apricciate the help. ( sorry for the long life story just giving u most of the info.)