What muffler you running again?Here are some old ones. Will get new videos when I finally get new 8 rib pulley conversion and Walbro fuel pump installed to address fuel starvation at WOT, and then will do some pulls. Running around 3.8 s 0 to 60 with old build. 426 should be faster just can't do full WOT runs yet because of fueling & belt slip issue.
Video of exhaust idling.
Video of 40 mph acceleration (old SC stroked 5.7 motor)
Video of sticky lifter (426 build that had to come apart yet again - it was a long road LOL).