My older ('86) 454 C3500 High Sierra 3+3 runs great but will diesel badly when hot. When cooler, it idles lower & shuts right off but when hot it seems to idle quite a bit higher & will keep running even with ignition off. Often it ends with a bang or two!
I replaced plugs, wires, & coil. It had an Accel 140005 HEI coil but after a little research, I figured out it was the wrong one & bought the 140003. The former owner had swapped two wires so it was running but the manifolds were red-hot! I got the firing order straightened out, figured out the 'wrong coil' thing & got the manifolds to run cooler but now it back-fires on shut-off (after dieseling for a few seconds). That actually started when I got the wires on correctly, believe it or not.
Any suggestions?