I have about 5-6000 or so miles on a new engine rebuild. Did some routine maintenance now, changed oil, pulled the plugs to do compression test - 150-165.

Noticed odd plug issue - they were dull green on the ground electrode. I know red is that stuff found in octane boosters, but whats green? I run straight chevron regular gas without any extra stuff in tank. This isn't a spotted green, but fairly uniform on the outside of the ground electrode facing the piston.

Coolant is Zerex G-05 - clear with yellowish tint, not green. I topped off coolant level and will keep eye on it just incase thats the culprit.

Also see some specs that appeared shiny. Maybe leftovers from the machining process? Oil has been changed more then once before, but these are the plugs (ZFR5N) I first put into the motor. I don't think the motors detonating - granted I don't think I've experienced detonation but judging by how I've read the sound as being described like a firecracker or metal bb's on a tin roof, my motor isn't. I've heard a knocking like sound from the motor under load when cold, but its hard to replicate and doesn't seem to be as sharp inside the cab as detonation is described.

I'll try to take some pictures if the plugs stay like this the next time I pull them.

My only guess without seeing the color would probably be sulfur deposits. Some gasolines have sulfides in them and will appear a greenish yellow. Could also be high speed glazing of some kind- where the plugs experience a sudden rise in temperature upon acceleration. You did say that there was a minor problem upon accelerating under load while cold. Worst case scenario, you may need a colder plug. Let's see a pic so we can get a better idea though.


Russ

High-speed glazing is pretty much a thing of the (distant) past—it mostly occurred with leaded gasoline, for it was the Lead halides that glazed the ceramic plug insulators upon sudden temperature rise.

Coolant doesn't usually leave a greenish-yellow deposit, it generally leaves a brownish-tan sandy/crusty deposit.

I'm also guessing it's just an artifact of whatever additives Chevron are putting in their gasoline nowtimes and probably not much to worry about if it's just a thin layer and not a big goopy crust.

Tiny metal globules, on the other hand, mean you need to check carefully for pinging/detonation!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Heres the best pic I could get of the plug. Camera is craptacular at best....



Pic isn't as bright as it should be but you can make the green out on the electrode and a bit on the base of the threads.

I think it is the gas, because on my intrepid that uses chevron gas, put new plugs in it few hundred miles ago and its starting to show signs of the same green as well.

About the detonation - the side of the electrode is feeling a bit rough/pitted too. Maybe I am getting into it. With 60thou shaved off the block and 2 off the head perhaps one step colder is in order? Or run super instead of regular.

On that note, what is one step colder then zfr5n? I know the higher the # the colder for ngk - quick search shows theres zfr6f-11, zfr6f-11g, zfr6j-11. Not sure what the difference is between the first two. The j version has more positive electrode exposed. They all have less porcelain showing then zfr5n so I'm not sure if they will be direct swaps.

I just did a bit of tuning today on Beater Valiant and it has Autolite 985's in her...I found an intermittent misfire on #1 for some reason and I suspect the plug wires are due for replacement. Anyhow, I pulled the plugs to read them to see if any were fouled, and no fouling present, they are nice and clean but have that nice "green" patina to them like you described. This car get's occasional Chevron gas and more often than not, the 10%+ Ethanol Content gas at Union 76 on the corner...I suspect that it's the result of the '76 gasohol and the additives, my '76 Duster I run strictly on Chevron and it doesn't have the green look to them...

???

-D.Idiot

Gasohol eh.... I wonder if chevrons putting any alky with the gas here in california. Hmm that may screw with my afr readings....

Come to think of it one of our cars doesn't use chevron, may have to look at those plugs. I just freaked out when I saw green plugs. I think I'm going to try the ZFR6F-11 plugs.

All gasoline in California contains alcohol

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Oregon is not far behind...the powers that be have decided to build two ethanol batching plants here so we have readily available fuel (since we have a nice pipeline of natural gas). Can't wait until the sky gets browner from the formaldehyde combustion leftovers...

-D.Idiot