Hello, I have a 383 with 10.5 compression, comp cam xr288hr, 1.6 ratio rockers, afr 195s, Edelbrock Q-jet performer manifold, rebuild Q-jet that was done by Quadrajetpower, and a 4 speed. I have the timing at 26 at idle, 36 total and running 10” of vacuum advance connected to a manifold port on the carb. I have a MSD pro billet distributor and I’m using the lightest springs with stock weights for the advance curve. I currently use an Autolite 3924 spark plug. The car doesn’t hesitate even when at WOT and never runs on. The idle is set at 750 and it runs great but sometimes when I’m cruisng at let’s say about 2500 it’ll surge almost like I’m letting off the gas but if I give it more gas it’ll pick back up immediately. I was thinking about changing one of the lightweight springs to a medium spring but the timing isn’t advancing at idle I believe because on my other motor I wasn’t able to bring the idle down this low because they were so weak.