I'm trying to start a new 383 for the first time tonight and I get the occasional pop and backfire, but it just won't start. I have spark and fuel, verified that the rotor was pointing to #1, and it was at TDC when I began trying to start it.

I put the paperclip in the A+B terminals on the ALDL terminal, unplugged the EST connector, turned key, waited 30 seconds and tried again and again. Still no luck. I've tried turning the distributor both ways with the timing light hooked up and it seems to want to fire but just isn't.

I did a search and found this post, which sounds a lot like what my motor is doing.

I took the advice stated there and backed off the rockers 1/4 turn 2 different times thinking they might've been too tight, but still no luck. (A couple of the rockers actually have some play in them afterwards)

I'm not sure what to check next.

 

You probably have the distributor in the #6 firing position. If you have the timing mark up and rotor pointing at #1 spark plug wire, turn the crank over one more time and line up the timing mark, and you'll see the rotor pointing at #6.

Lift the distributor up, turn the rotor 180 degrees, try it again.

 

Yep, it was 180 degrees off. Thanks man!