Re: Octane ping
351, detonation and "ping" are two completely different things. Detonation occurs when the air/fuel ratio is too lean. The lean mixture actually causes an explosion rather than a smooth burn of the fuel/air mixture on the power stroke. Detonation can cause serious damage (i.e. holes in pistons, etc.) in a matter of seconds but "pinging" cannot.
Using a lower heat range spark plug, will have no effect on the knock problem. The conditions that caused the engine to knock will still be present regardless....
Knock aka pre-ignition is just that "pre-ignition." It takes place before the spark plug ever fires so a spark plug change would have no effect. Sometimes it's caused by carbon buildup in the cylinder, by using a fuel with a lower octane rating than that required, incorrect ignition timing, as well as by compression ignition alone.
When the air is compressed in the cylinder, it heats up. (PV=RT) If the octane rating of the fuel is not high enough, it will auto ignite before the spark plug ever fires. Obviously, if the fuel ignites before it should, it will be burning as the piston is moving towards TDC which is what causes the knock.
However as you said, using a thermostat with a lower temp rating would help by lowering the operating temperature of the engine as well as the air entering the cylinder thus reducing the likelihood of the autoignition temperature being reached which could get rid of the "pinging" problem but I personally wouldn't recommend it. The engine needs the higher temps to approach more complete combustion to lower emissions and increase efficiency and the computer is programmed for the specific temp range of the stock thermostat.
If Ford can't (or won't) reprogram the PCM for a little less advance, get yourself a handheld programmer and do it yourself.
End engineering psycho babble..... :-)
1992 Ford Bronco
E4OD- B&M Stage 2 shift kit
Full 3" stainless Bassani Exhaust
32" BFG's/stock suspension
"No replacement for displacement."
"Our lugnuts require more torque than most Honda's produce!"