Mythical art of plug reading (help needed)

[Kivyee]

Hello Peeps!
Since it's a rainy day here I decide the next things to start looking into is to see what the plugs are telling me about the running condition of the car. It's been about 20-30km and not much driving since I've started to adjust the carbs and moved the vacuum advance to port vs timed (i.e. more timing at idle). The car was definitely running rich before, and is probably still rich but less so now. I only did 2 plugs for now just to see what I find, will probably pull the rest later.

Car has around 9300km at this point, plug likely have been in since rebuild.

Here's what Cylinder one plug looks like:
cyl 1 042826.jpg

And cylinder 5
cyl 5 042826.jpg
cyl 5 042826 - 2.jpg

Gap is at .35 (a little low isn't it?) and its a NGK Vpower R5671A-8.

What I'm seeing is:
1. Running rich (carbon build up)
2. Some carbon build up on the electrodes, especially Cyl 5 on the case of the side electrode

I don't have enough run time on the "new tune" to see if its leaned out yet, but looks to me like the plugs are too cold? Would appreciate your opinion!

[Presdough]

The gap looks a little narrow and I suspect oil residue. How many miles on the engine, and what ignition system are you running?

[rich grsc]

Those look bad.. Much of that can be caused by short trips, and or long idling periods with a rich mixture. I am NOT a fan of NGK plugs, they always fouled easily in my experience. Try some Autolite plugs, also get a slightly HOTTER plug, that one could be too cold. Maybe open the gap to .040

[Kivyee]

9300km on the engine since rebuild, and using a HEI ignition.

[StangRacer]

That looks like you may be getting some oil in chambers... I assume you are running pump gas. I always found it very difficult to get a good read on plugs with pump gas. If there is any idle time reading the plugs is not helpful to tell you what is going on... The best thing to do would be throw those plugs out and start with a new set to read.

The way to read plugs is to get on a good stretch of road and take it up through third gear, turn the engine off, coast to a stop, and then pull a couple of plugs. Get an otoscope so you can look down inside the plug at the fuel ring. Again, with pump gas this will be very difficult to see and may take a few runs to get it established. The heat mark on the strap of the plug will be a good indication of where you are as far as timing is concerned.

Also, as Rich suggested, try opening the gap up. I am sure he meant to .040... An HEI ignition shouldn't have any problems with an .040 gap.

My preference with plugs was the opposite of Rich's, I prefer NGK's. Maybe because the engine I learned to read plugs with had NGK's so I always stuck with them. I am sure Autolites would serve you just as well.

[BornWestUSA]

"Reading" is best done with new plugs under controlled conditions.

I used a lighted magnifier made by Champion spark plugs to get a good look at the insulator. (similar to this)
https://www.pegasusautoracing.com/pr....asp?RecID=209

I have not done it since road racing two stroke Kawasaki triples!

Those just look nasty. Time for new ones. I like NGK v power. I use FR5's (7373) in my aluminum headed 427W.

[rich grsc]

Yes, .040, a typo mistake, and it is time to replace those unless you have an old style plug 'blast' cleaner. Glad you guys had luck with NGK's, I still won't use them though

[Kivyee]

Thanks for the comments folks! I have a set of Autolite AR3924s on order now - from my understanding they should be a couple heat range up from the -8 on my current NGK plugs.

[Railroad]

What engine are you running? Might want to check your pcv system for pulling oil into the intake flow.
good luck,