How can the old plugs have a bigger gap after 2 years??? I did the tune up about 2 years ago(100K) new plug wires too(just checkin' to see if you're awake)and last june it started running "funny", after a couple of days it set 2 codes 307, 316. 307 #7 misfire #316 i dunno? I bought a set of the coils off the ebay guy, and a new set of Motorcraft plugs, and had at it. When I pulled the old plugs out the plugs all looked good (a bit whitish) but no corrosion or burnt electrodes, though the gap looked looked a lil big. All were around .062 - .065 except #'s 1 and 7, they were .072 and .076 respectively!!! I set the gaps myself ( I've done all my own work - which isn't much-just the consumables, it's been a great truck, thanks Gerald oops wrong family. Anyway, have ya ever heard of the gap getting bigger? I just changed the coil on #1 tonight (code 301) plug was good(coil maybe went bad - I kept the old ones, just in case)

 

the gap grows over time and I've pulled plugs were it had grown to nearly .0100. Normal.. Back in the day of low voltage point ignition systems you would have to tune your car up ever 25 thousand mile because of that. Plug gaps was like .32 and cars would run bad if it got much bigger.. Not really an issue with modern ignitions. I've seen engine go 160k without a plug change..

 

Why would you not expect a spark not to errode metal tips each time the coil fires? Same type condition as welding consumes the electrode but at very low power levels in the ignition.
It depends on the plug metal material as to how fast the tip and ground strap will errode.
Combustion errosion is also a factor.
As for electrode condition by sight, an FI motor will always look like it is running lean because the OX sensoros keep the A/F so tight and actuaaly a bit lean whenever possible. (EGR operation in OD)
Except for fuel additives and quality, the tips should stay fairly clean and a bit whitish.
Good luck.

 

My 98 did almost the same thing after modifying the intake and exhaust. Plugs were a little whiter and had signs of ware @ 30,000 miles. Not that bad tho. The pre-gap is .54, they were .56 when I changed them. Running Denso's (Iridium's) now, - I should be able to get 50,000 (healthy miles) out of these I figure... Maybe more.

NOTE: - When I was stock, all factory components, the plugs lasted allot longer and weren't as white from what I recall.

 

Sounds plausible, about the higher voltage and leaving them in longer - I'll buy it. It's sure a good thing we don't have to change these every 15k like the old days (seems more like it was plugs, points, & condensor every 5 to 10k - and cap and rotor every 15 - 20k)
There was no corrosion(as stated in the original post) just the gap was bigger; and no, I would not expect any - modern engines, better A/F ratios, spark, etc; todays fuel - probably "better" as well.
I wonder how the truck would run on the old GULF premium (104 octane) at $.36 a gallon ,I used to run in the BOSS 302 in high school --yeah, wish I woulda kept that one!!!
Nice Mach jethat!

 

The engine would run exactly the same on 104 as it does on 87 unless it was tuned to take advantage of it.. By itself higher octane does nothing.