Although my truck starts, runs, and drives fine, I decided to change plugs, cap, rotor, and check timing @ 253,000 miles

8 Autolite AP 25's plus cap and rotor - I did locate spout and disconnect, but sun was so bright in my driveway couldn't see marks on damper

All plugs were spot on tan color but center electrode way short and gap at 080, new plugs set at 0.054

loosened distributor clamp and tweaked a small amount to increase rpm

My question is about the black exterior part of the plugs, which looked like they've been in there for years

Again, ran fine and runs fine but how long for plugs to look like this? burnt to a crisp?

 

I have no idea why you loosened the distributor clamp, moved the distributor to increase your RPM??? You just messed up your timing.

 

Failed to mention I had timing light hooked up! Bumped it up to 13 degrees btdc

Engine is purring, running/driving like a new one...

 

Advancing the timing is not the way to increase idle speed. All you did was mask over an issue if your idle speed was too low since the idle speed is controlled by the computer..

 

Put it back to 10degrees with out the SPOUT. The ECU will take care of the timing just fine. If you are rich or lean, figure out where the problem lies. Do not throw parts at it just because you think it might help.
Pull the codes and post them. Somebody here can help get it straightened out.

 

Take it easy men
from original post: Again, ran fine and runs fine but how long for plugs to look like this? burnt to a crisp?

from earlier today: Engine is purring, running/driving like a new one

And no codes whatsoever getting 16 mpg too

Could some address original question re plugs? Gap out of spec by 50% - that's throwing parts at it???

 

Try not to take the previous response's personally Apple. You don't have to listen to them, but perspective is always valuable; their comment here may help someone else with another issue when they do a google search.

To comment on your original question; I'm no mechanic, but extremely burnt plugs suggest carbon fouling which can be caused from rich air-fuel conditions. Check your air intake and fuel delivery. Start at the air intake and work your way through (there is an oil filter in the intake as well). Idle control valve, Map sensor and air temp sensor get old and don't read accurately affecting air intake.

Next would be to check fuel delivery; fuel injectors, Injection Pressure Regulator(regulates fuel rail pressure), fuel filter(though it wont cause it to run rich, could cause it to run lean). All of these can affect your fuel to air ratio.

I see it a lot, "if it aint broke why fix it". That personally is not my approach or mindset. a 30 year old valve is not going to work like a new valve, period. I'm in the process of restoring a 92 f150 5.0 and I've got it sounding and driving like new as of yesterday.

Feel free to message me if you need to bounce ideas. Best of luck!