a trashed 96

i just got a 96 cavalier from a guy for $50.00..
man have i got some work...
the front was damaged from hitting a deer stand on the road..
so now it needs a radiator ..coolant fan...the thermostat is shot...
so im running with out one for now..i put a piece of pizza hut pizza box in front of the radiator to keep it some what warm... right now its cold enough to run with out the fan...
the exuast is fallen and wired up..going to replace it with 2" pipe.high flow cat and a cherry bomb glass pack muffler...
i got a K&N filter and made a new intake box ..that alone almost doubled my fuel milage...i switched over to synthetic oil wich made it run smoother and gave it great response off the line...
the stock muffler was almost stopped up so ive got it cut out and im running a strait pipe till i get the cash for new exuast...
now heres a question..ive got this rattle in the engine at first i thought it was the valves..but its not...
it sounds like its comming from the timing chain...
is there an adjustment arm or something in there that has broken?
it doesnt do it all the time..its not there whenn first strated..after it warms up it really starts to chatter...
any ideas?
thx