Timing Curve on 360 in an RV

Slow the all in to about 2800 rpm, if you have a adjustable vac advance try to delay it to come all in later.
Awesome, will give this a shot. Currently have vacuum advanced set to zero. Played around with 0-5 degrees of vac advance, but pulling it back to zero helped with backfiring. For some reason, anytime my timing started getting into high 20’s, I was getting backfiring.