Thoughts on oily/sooty spark plugs

[WissaMan]

This is a 77 New Yorker with a 440. AVS2 650 carb (adjusted pretty lean I think), new Mancini electronic ignition, new plugs, new wires. Seems to runs well for the most part, but upon checking the plugs, some don't look real great. Most have an oily residue in the threads and some look carboned up. This is after only about 200 miles of mostly around town and light-foot easy driving. I got around 9mpg on my last tank of gas, but from what I've read around here that's typical town MPG for these cars.

The car has 156k miles on it, but I did a cold compression test and all cylinders registered nearly identical at 110 psi. (I did forget to clamp the throttle blades open, but it's the consistency I'm more concerned about). It also doesn't smoke at all on start-up and the oil stays relatively clean, but it does seem to use some oil.

 

[Toolmanmike]

Those are pretty dark. I would say running rich. Any blue smoke from the tail pipes? Double check your heat range conversion because you are running NGK's. A 650 AVS2 shouldn't be too big for a 440. Have you tuned it with springs, metering rods and jets or just adjusted the idle mixture screws? How about a fuel pump replacement? Has that happened lately?

 

[Big_John]

This is after only about 200 miles of mostly around town and light-foot easy driving.

They do look a bit dark, but around town and idling might be the issue. Go out and run it a little hard and then check the plugs. That will give you a better idea.

 

[WissaMan]

I did buy a tuning kit for the AVS2 and as of now I have the leanest rods in it. I kept going leaner a step at a time as long as it felt like it was running ok. I think I have the one step looser springs in the rods. At this point I feel it is one step too lean because it hesitates a bit when cold, but when at running temp is seems to run fine. I also tuned (tightened) the secondary flap because it was opening up way too easy at the out-of-the-box setting. I got on it the other day leaving a parking lot with my brother observing and he said it did puff a little smoke, but nothing that looked out of the ordinary or concerning.

I'll double-check the plug #'s -- I bought them at the local Autozone and just had them look it up, so I suppose there's a chance they're wrong.

I'll "blow out the carbon" tonight on the drive home and check a few of the worst looking ones

 

[stain]

What is your timing set at?

 

[Gerald Morris]

I did buy a tuning kit for the AVS2 and as of now I have the leanest rods in it. I kept going leaner a step at a time as long as it felt like it was running ok. I think I have the one step looser springs in the rods. At this point I feel it is one step too lean because it hesitates a bit when cold, but when at running temp is seems to run fine. I also tuned (tightened) the secondary flap because it was opening up way too easy at the out-of-the-box setting. I got on it the other day leaving a parking lot with my brother observing and he said it did puff a little smoke, but nothing that looked out of the ordinary or concerning.

I'll double-check the plug #'s -- I bought them at the local Autozone and just had them look it up, so I suppose there's a chance they're wrong.

I'll "blow out the carbon" tonight on the drive home and check a few of the worst looking ones

Try "steam cleaning" your cylinders, and de-gunk that AVS2 if it's been on there for some little while, then check your plugs. Maybe replace one or two with brand new ones after the cleaning, then watch these in addition to the others for comparison. One last possibility; is your ignition system delivering good spark?

 

[WissaMan]

Timing is about 16~18btc at idle I believe which it seems to like. I was experimenting with it and at 20 I got a slight ping under load. I think spark should be good, everything is new and it's getting good voltage at the coil (I think it was around 8v when I checked it several weeks ago but I can check it again to be sure). The AVS2 is also quite new, replaced by the PO not too long before I took ownership.

I have a hand-held wideband O2 gauge with a tailpipe sensor. I had used it to tune the idle but this evening I put it in the pipe and ran it into the cabin and took it for two short drives. First drive I had the secondary flap fixed so it wouldn't open. Second drive I undid that. What I discovered was that at light throttle cruse it was nicely lean (about 15-16 AFR). At WOT with the secondary fixed shut, it'd dip into the 12 - 13 range which is a little rich but ok. But with the secondary working, it would drop into the 10's and 11's which is way too rich and I could feel it. Exhaust note would get loud but not much acceleration to go along with it. So I think either the secondaries are still opening too early, even though I have the spring pretty tight, or the jetting in the secondaries is too fat. I'll tinker with those two things next. The kit has two jets that are leaner than the ones that came in the carb so I may try one of those.

 

[413]

Looks like 2.7 rear end gears and putting around town. Get the RPM up, maybe leave it in second gear in town.

I had a 440 that did that with 2.7 gears, swapped to 3.23 and all that black plug stuff went away and the mileage improved also.

 

[CBODY67]

Aside from all of the other tuning issues, I would be concerned about tha VARIATION in ceramic coloring. Some look a bit cool as others are "black".

That some look decent tends to indicate that the NGK heat rands is pretty correct, to me. The NGKs cover TWO Champion heat ranges, usually, so I feel their heat range is more tolerant of things than allegedly more specific. BTAIM

Note, too, that NGK heat ranges run in reverse to other spark plug brands. For your application, an "XR3" would be hotter than your current XR4s.

When installed, the threads should have a drop of oil on them to start with. Just like any other spark plug, for that matter. If there is oil migrating up the threads from the combustion chamber, THAT is another issue.

There is a difference between sooty (rich or incomplete combustion) and oily (valve seals/valve buide from the topside or rings if from the bottom side, or combinations thereof).

The "stuff" that was observed by your passenger on hard acceleration is probably NOT due to engine wear, but accumulation of particulate matter in the muffler, collected from normal driving, which is "blown out" when exhaust flow though the muffler suddenly happens. A better gauge would be to have somebody follow the car after a long closed-throttle decelleration, looking for "smoke" and its color.

I concur with @Big_John , get the car out on the Interstate and run it. It can take a good 1hour run, one way, at 65+mph to get all of the stuff cooked out of your round-town driving. Take your wrenches with you. After the cruise, off-ramp to some place you can park and eat. Then check the plugs that were the darkest. One or two, not all of them. Also check a few of the ones that were more-white on the ceramics, for good measure. See what things look like then.

Please keep us posted,
CBODY67

 

[Gerald Morris]

Looks like 2.7 rear end gears and putting around town. Get the RPM up, maybe leave it in second gear in town.

I had a 440 that did that with 2.7 gears, swapped to 3.23 and all that black plug stuff went away and the mileage improved also.

Yeah, I run the same 383 now with 3:23 gears as I did w 2:76, and in town it does better, no 2 ways about it!

 

[Gerald Morris]

Timing is about 16~18btc at idle I believe which it seems to like. I was experimenting with it and at 20 I got a slight ping under load. I think spark should be good, everything is new and it's getting good voltage at the coil (I think it was around 8v when I checked it several weeks ago but I can check it again to be sure). The AVS2 is also quite new, replaced by the PO not too long before I took ownership.

I have a hand-held wideband O2 gauge with a tailpipe sensor. I had used it to tune the idle but this evening I put it in the pipe and ran it into the cabin and took it for two short drives. First drive I had the secondary flap fixed so it wouldn't open. Second drive I undid that. What I discovered was that at light throttle cruse it was nicely lean (about 15-16 AFR). At WOT with the secondary fixed shut, it'd dip into the 12 - 13 range which is a little rich but ok. But with the secondary working, it would drop into the 10's and 11's which is way too rich and I could feel it. Exhaust note would get loud but not much acceleration to go along with it. So I think either the secondaries are still opening too early, even though I have the spring pretty tight, or the jetting in the secondaries is too fat. I'll tinker with those two things next. The kit has two jets that are leaner than the ones that came in the carb so I may try one of those.

Leaning your secondary jets out 1 more bump might help. I need to get that spring-rod-jet kit myself. A November-December job, here. I'll be watching your progress in this with interest. I wonder if retarding the timing a little for in town driving might do you good. That much advance would be better for higher revs I think. I keep mine around 12-14 degrees BTDC and it seems happiest there, in the city....

 

[413]

Timing, very good.

How is the timing chain with so many miles? If that is original then the cam timing will be late, not helping deiveability with those hiway gears.

 

[WissaMan]

This car has 156k miles on it, but I suspect the engine may have been rebuilt at some point since the compression numbers are perfect and the oil stays pretty clean. We have a 68 that has 100k miles on it and the oil goes dark pretty quickly. But I don't know it for a fact. The PO didn't have it done but this car has been through several owners. But the oil in the plug threads makes me go "hmmmm". I read in a different thread here about the possibility of the oil rings getting gunked up if the car is only driven on lots of short slow trips. Even my drive to work is only 25 minutes of easy driving, so getting it out and opening it up I'm sure would be a good thing. I also saw mention of some oil additives that can help clean up the rings.

I hear you on the rear gears. With those and the low stall converters they put in em it's almost like you're starting out in 2nd. I'd really like 3-something gears and an OD....something on my long long term wish list.

I'll revisit the timing after I get the fueling where it needs to be. I've read these low compression engines respond well to more advance than the factory spec and I felt this one has. But once the fueling is sorted the timing demands will probably be different.

 

[mr gtx]

what size metering rods are in there now ? are you running a vacuum advance ?

 

[CBODY67]

How much throttle is being used in the testing? ANY AVS (! or 2) air valve should not be opening in non-WOT situations.

Most of the "trouble trees" used now (and quoted by many) were probably configured 80 years ago. When normal motor oils did NOT have all of the detergents that even 1970s motor oil had in it (unless some no-name "oil" was used). Since the 1970s, many more detergents have been used to keep the inside of the engine clean.

What is the engine's normal oil consumption? Another marker for how well the oil rings are doing their job. On our '66 Newport 383 2bbl (150K+ miles from new, non-rebuilt) and my '70 Monaco 383 4bbl (same mileage), the oil darkens in a normal manner and time. NO oil fouling of the spark plugs OR dark ceramic colors.

Will the edges of the piston crowns be "washed" clean around the edges? Probably. But not enough oil use to foul a spark plug. One or two, but not 4 of them.

AS most of the driving is done on the primaries, worry MORE about how the plugs color in that driving mode. Which is what the highway driving mode is about. Stay out of the secondaries.

Other than changing the secondary jets, you can also enlarge the main air bleeds for the secondaries. The small holes in the venturi are also a calibration point. Smaller holes - richer mixture. Will not take much! Once done, no going back, though.

What intake manifold is on the car? Just curiious.

CBODY67

 

[USSMOPAR]

That engine is a pig, the plugs look terrible, I would expect 12 -15 mpg at a minimum.
As usual there are critical unknown factors
Operating temp?
Timing chain stretch
Valve seals?
Is the interior of the intake manifold wet with gas?
Quality of the spark plug wires

 

[WissaMan]

I put the smaller jets in the secondaries and did another test with the wideband. What I noticed was during a WOT pull the afrs would be okay at first but then drop down into the 10's after a few seconds...same as before. After giving it some thought, I put my hand on the intake where the exhaust crossover is and it was only lukewarm which made me suspect the crossover was blocked off. I know some people think that is a good thing to do, but I remember doing that on a 440 when I was a teenager (40 years ago) after reading about it in a magazine and it made the car run worse. I think it causes fuel to puddle, which is just what USSMOPAR mentioned above. So I removed the stock iron intake and yes, the pan gasket was the type with the crossover blocked. So I punched holes in it and put an Edelbrock aluminum intake on it that I had sitting brand-new on the shelf. I ran out of time and didn't get a chance to check it with the wideband but I'll try and do that tomorrow to see if that had an effect. Yes, I know, changing multiple variables at once isn't the best for troubleshooting but I really didn't feel like doing the manifold R&R twice.

In answer to some of the other questions:

Spark plug wires: I forget the brand, but they came with the car brand new in the box and I put them on shortly after i brought it home
Timing chain: unknown
Valve seals: unknown
Operating temp: unknown. But I will be getting one of those little triple gauge sets
I'm running vacuum advance using the "timed" port
I have very lean metering rods in the primaries, possibly the leanest in the kit

 

[WissaMan]

I would add -- when I first got the car, the plugs would foul so badly after just a few miles it would start missing like crazy, stall out, etc. What I discovered was whoever got rid of the lean burn (it wasn't the PO, it was a previous owner to him), when they put the new ballast resistor on, they wired it in series with the original ballast resistor and thus the coil was only getting about 5-6 volts. After I corrected that, it was a night and day difference. But that still might suggest some underlying issue, just that now with a good spark the plugs don't get so bad that it misses.

 

[Toolmanmike]

I would add -- when I first got the car, the plugs would foul so badly after just a few miles it would start missing like crazy, stall out, etc. What I discovered was whoever got rid of the lean burn (it wasn't the PO, it was a previous owner to him), when they put the new ballast resistor on, they wired it in series with the original ballast resistor and thus the coil was only getting about 5-6 volts. After I corrected that, it was a night and day difference. But that still might suggest some underlying issue, just that now with a good spark the plugs don't get so bad that it misses.

Just curious as to what distributor you have in the car? When you remove the lean burn system, the distributor should be changed as well.

 

[WissaMan]

When I got the car it had an old points distributor with a leaky vacuum diaphragm. However, a brand new Mancini electronic ignition kit came with it and I installed it according to the instructions (set the gap, made sure it has a good ground, proper voltage, etc.)