will start sometimes

[powder1]

i bought a 240 sx in great condition all except it didnt run.it had been sitting guy i got it from got dui well he said his sister drove it and it died never ran again i brought it home tinkered with it got it to start. wont rev but only starts sometimes after sitting or after i depressurize the fuel lines. and when it does start its got some bad noise coming from the head. not like a rod knocking not that bad. but a noticable noise. any ideas why it starts after i do those things to it and why it wont idle i feel as though i may have a crack head or maybe some bad valve seats so tell me whatcha all think. thanks.