So hopefully this helps…I have 2 dodge 4.7 and had 1 3.7 (same engine minus 2 cyl)
1st is an 04 ram 4.7
2nd is an 02 ram 4.7
3rd was 99 ram 3.7
In ALL these I would occasionally get random misfire codes (champions from autozone), pull everything apart, used scan tool to test fire coil packs, test/check sensors etc etc
Replaced plugs, fine for a while then start again, all 3 right around 20k miles on plugs…changed plugs another 20k then random misfire…this continued for 2 yrs on the 02 and 04 (sold 99)
For the 04 I went to Orileys and bought champs instead and on 02 bought set of Ngk from the zone
The ngks lasted about 40k the champs from Orileys about the same
So I’ve done some thermal checks with a dedicated temp sensor
Neither truck has ever overheated or run hot, both have factory thermostats, both thermos are opening on temp, coolants flushed., pressure test no leaks and on and on
So what we’ve found, with the coil on plugs in the 4.7, the thermal shock is coming after shut down
Metal to metal in the head the plugs are close to 300f, the exposed ceramic before the coil boot is about 225 when running, under the boot is about 295
When shut down occurs the metal thread on plugs after 15min is around 275 plug ceramic 160 and under coil boot is 260ish
We used heat shrink around the ceramic and reinstalled the ngk, the exposed middle ceramic stays more consistent with metal thread
All this said…these engines do have a thermal issue with the exposed ceramic on the plugs
In the 04 we stuffed standard fiberglass insulation around the plugs after install before coil packs and on the 02 we bought accell yellow high heat header plugs
In the end, champions from autozone have some issues, but champs from Orileys seems less of a problem, ngks seem to not care either way, and the accell high heat yellows are going strong
Both trucks after 45k on current plugs, 1 with insulation added and 1 running high heats with no insulation