What causes it?

I've cleaned one set of plugs and put new plugs in twice in the past year. The plugs I take out have a black gunky substance all over them. I have a spare 350 w/ HEI in my garage. I stole the coil from it and slapped it in my vette. No help. I have replaced the ignition wires. No help. After I put new plugs in, gapped to 45 per instruction of the little sticker under the hood (1979 L82 Auto), the car runs like a bat out of he**. But after a couple of months of driving around the neighborhood a few times, the plugs foul and the thing runs like junk.

I am using AC Delco R45TS plugs. The car is all original and all stock, except for a 180 degree thermostat and new aftermarket off the shelf ignition wires. My timing is set to 12 degrees advance @ 700 RPM. When I set the timing, I make sure to unplug the vaccuum advance hose w/ a golf tee. I can't think of much else to tell here, except that I run 91 octane gas. My air filter is clean, I have installed a new fuel filter, and I change the oil often. The vette has 38,400 miles on the clock. It uses no or very little oil. There is no oil in the antifreeze, and no water in the motor oil. Any ideas of what to check before I pull the Quadrajet and rebuild it? (Thinking about sending it to Lars anyway)

I would like to get to the bottom of this problem, because I am sick of scraping up my hands putting new plugs in this thing.

 

my guess is you are running rich? try to lean it up a little bit. :)

 

Guess I'll take my handy Doug Roe Rochester Carburetor textbook out to the garage and try that. Thanks, Jenny!

 

Gunky? Sounds more like oil fouling than gas to me. A lot of cold starts and and short trips can cause wet plugs but an HEI in good condition shouldn't have any problem burning them off. Are you getting any smoke? If so, what color and when does it occur?

 

The only smoke I get is a brown-blackish smoke during warm-up. It is not blue smoke, it is more like smoke caused by choking. Plus, it only does it when it is cold outside, pretty much anything below freezing. I guess I should also have noted that the black gunky stuff smells like fuel... so maybe both of my HEI's are in bad condition? I just always wonder if I am not getting a hot enough spark.

I've been thinking about getting an Accel performance cap and rotor assembly and an Accel HEI coil... just need to cough up the cash to do so. Of course, that means I need to get better quality wires, and then the mod-o-rama goes on from there.

 

I was just thinking... a picture says a thousand words?
http://www.gnttype.org/techarea/engine/plugs.html
http://www.mechanicmatt.com/SparkPlugChart.shtml

:) Good luck

 

Splash fouled. Makes sense too, since I have let it idle sometimes without driving, usually when tinkering with it. I think it may be a combination of this, and the carburetor set up too rich.