I had some backfiring from my 283 prior to a complete new dual exhaust, now no backfiring on engine braking. Point being, do you have exhaust leaks near the engine, on deceleration it will suck oxygen into the exhaust leak and backfire.
No exhaust leaks present that I can tell. No carbon tracking at the head/manifold and I periodically check for exhaust and vacuum leak here since I know the manifolds like to loosen or warp with time. Its all brand new stainless single out exhaust to a Massey Ferguson muffler and downpipe right under the cab. Same setup as prior to the HEI.
Just had a nice long talk with Jerry who was beyond helpful. Im thinking the current advance setup still needs fine tuned so I am going to focus on that and see if dialing it in lessens this phenomena. I've got a nice 2.5 hour drive on Friday with the truck to pickup a water tank in Gary and plan to tinker with the advance and total timing during the drive to see how the truck responds. It may take a minute with trial and error but ill report back with what I find/learn in the process.
