help pleaseeee

How about this one guy.. A less greasy option. With your 1 1/4" socket on the crank bolt remove the distributor cap and watch as you move the crank back and forth till the rotor moves. See how many degrees "slop" you actually have. The backfire under load is usually indicitive of high secondary resistance such as an "open" plug or coil wire or an extreme lean condition such as low fuel pressure or stuck metering rods. Other culprits include a bad ignition coil... yes they do fail or balast resistor issues. I had an Accel Super coil go south one time and the car would run but only with the timing way advanced making me think like you that the timing chain had slipped..... See what kind of gap your spark will shoot.... should get a good 3/8 " without any trouble.

BD