Timing for Buick 3.8

In my "winterizing" of my Jeep, I decided that it's time to do something about the backfiring on the starboard side of my 80's Buick 3.8 liter. Been looking around the web for some timing numbers, but have not had much luck. Anyone know what it should be set at?

Just to cover my bases, I've replaced plugs, cleaned cap/rotor, and checked that the plug wires were in correct order. I really only notice the backfire when ideling at a stop lights/whatever. While under power, I can't hear any backfiring, or at least can't tell if it;s popping or not. I also think the carb is loading up a little while idleing, but I don't know how to lean a carb either...

Dondo

 

From what I've read, specs for a 231 buick is 12 degrees. I'm not positive on that, but my '76 buick 231 runs good at 12.

 

My 84 buick w/ stock hei calls for 15*. I just installed the D.U.I. distributor and it call for around 20* because of the hotter coil.