Hi Everyone, I'm a new member with my first vette. It's a 1980 and I will be putting up some pictures and an intro thread eventually, but for the moment maybe you can answer something for me.

I've got a bunch of little questions but lets start with this one.

I changed out the old plugs (ACDELCO R45TS) to put in the E3s that were recommended at the shop, and I actually had the forsight to note which plugs came from where. This is unusual for me...

Anyways, as the title says, the spark plug in #8 is black/soot/charred on one side. The rest of them are white to grey, but now that I look a little closer I see that some of them have a slight colour bias, but not like #8.

Here's some info, to the best of my knowledge. Don't know about the guts or cam, but it has:

14x3" air cleaner
Holley 6619-1 600cfm "emissions" carb
Edelbrock C3BX (late model, no 3bbl cut out, dual bolt pattern)
Headers of unknown prodigy feeding
True dual, no cat exhaust with "midas special" crappy mufflers

Just had the carb rebuilt and the distributor timing corrected so I don't really know when/how long the plugs have been like that or when they were installed

I can post a picture if you can point me to a preferred image host

 

I didn't see any questions in your post, but I will advise you to get rid of the E3 plugs and put the correct ACDelco plugs back in

 

You spent more cash for the E3's that won't do you any good.
I'm not sure what trans they used in 1980, but if it's a 350/350C, check the vacuum line to the trans. The vacuum modulator could be leaking into the vacuum. It's ported to the intake right over the 6-8 intake runner.

 

I've seen something like this as well. If it's on one side of the porcelan, could be oil coming from a valve guide? If the orientation of the plug were marked prior to removing the plug, the sooted side may point to the source?

 

Unless the E3 plugs are going to hurt something I don't image I'll be buying another set. I can't return them so I'll certainly be using them! I'll take that as a lesson learned next time, thanks.

Oh, I should also mention that I have no plans to race this car, it's a cruiser for the wife and I, I won't be measuring anything in 1/10s of seconds. Oh, and it's an Automatic, don't know the tranny designation though.

My question is... why is that one plug different?

You know what Tim, the vac line to the tranny ended up splitting while we were out of town for a cruise and I had to rev it up past 4000rpm and shift down to 2 and back to 3 to get it to shift into 3rd. I don't know how long it was cracked, but it started that as soon as I got off the highway after an hour of steady driving.. (Probably the longest steady drive it has had in years).

I replaced the lower rubber hose that connects the steel line to the modulator yesterday when I changed the plugs, and will be replacing the rest of the vac lines in the next weeks when our new seats and carpet arrive and we start cleaning it up.

As long as there is nothing concerning about the one odd plug then I won't worry about anything. When is a good time to check the new plugs for similar patterns?

Edit: I just looked at the pictures from when the carb was off and I see the passenger side intake has a lot of soot in it, while the other side is clean. There is a rocker cover vent hose connecting there so that might explain it as well

 

There's the sooty intake

 

The discoloration in the intake is pretty normal- look at where the PCV line connects- right outside of the color.

Pull the modulator line off and see if it's wet- it's the one with the 180* bend just between #1 and #8 plug wire in your picture.
Check the condition of all those vacuum hoses and your PCV valve to- just like you noted.
Don't worry about the E3's- just remember that everyday A-C Delco plugs work as well as any of the "performance" spark plugs.

 

That vacuum modulator tube will actually suck tranny oil up the tube and into the intake, if the modulator diaphragm has a leak. If so, that oil would end up in the nearest cylinder to that vacuum connector on the intake manifold....usually #8.

Run the plugs for a couple of weeks or so, then check #8 again. If it is still blackened, it's probably a damaged/defective valve seal for that cylinder.