I was thinking of this post as I drove the '75 Country Squire earlier. It used to behave exactly the same way. It has a 460 with the Edelbrock carb and Duraspark II ignition. I did end up installing a pre-1972 timing set in it to zero the cam, but after that, I could not seem to get rid of the bog/backfire that you describe. What I found was that setting the ignition timing to factory settings was not working.
I finally connected a gauge to manifold vacuum and advanced the timing until the gauge hit its maximum reading (20-21"). At this point, the engine was starting to miss, so i backed off the timing until she smoothed out and left it there. It was idling faster, so I turned the idle screw back down and adjusted the mixture for smoothest idle. This was all done with the engine at operating temperature and the advance hose connected to the gauge rather than the distributor. I also re-purposed one of the vacuum valves on the water outlet prevent vacuum advance at cold start-up.
This works well and the engine is a powerhouse. It has smooth, even acceleration and no longer hesitates/backfires. If you time it this way, you should be able to drive it warm without any detonation. If it does ping, retard the timing in small increments and test drive until the pinging is gone. My engine doesn't ping at all, but some slight pinging under heavy load is acceptable.
If it starts/cranks hard when hot, turn the ignition on and wait a few seconds, then crank it. This seems to allow the module to charge and retard initial timing as it was designed to do during starting. When I follow this procedure, the engine fires right up. Hope this helps...
1978 Lincoln Continental Sedan 460 V8
Last edited by landyawt78; 03-30-2019 at 01:59 PM.