jst98gtmustang

first off a few days ago i change the spark plug wires to ford racing 9mm wires.I didnt get a chance to start it the day i put them on so the car sat for a few days. well today i went to start the car and it turns over and cranks but the there a loud clunk noise and the car wont start.I put the stock plugs back on and it doing the same thing..I check the firing order on the plugs and they seem right.. I been having a problem with the battery keeping charge,it will sit a few days then be dead. I change the alternator and had battery checked out ok.

Any idea why it won't start what the noise could be?