89 240sx loud clunk and wont start?

[DarkDrifter95]

OK i just finished fixing the timing on the car it started up quickly backed it down the driveway n started to go around the block. Then i was in 2nd and at about 4,000 rpms there was a loud clunk and the rpms went down into a stall and the car wont start now? Help! I just got the timing chain fixed along with the cover. fuel pump is working fuses are good distributor spins wtf!? help

[sRscooby]

did you check the timing chain again? maybe it got off track or something