What do these spark plug say?

[Canadian1968]

Little back ground. I did the stealth HEI module swap inside the orange ecu box, gutted the ballast and got a summit E-coil. The car started right up, I'm running a wideband O2 and saw that it leaned out my idle so I adjusted the mixture and adjusted my rpm a bit and double checked my initial timing at 18*. Took the car out for a spin. It seems to be running great . I had a set of plugs that had basically no run time on them I gapped them to .40 and threw them in. I drove the car to work today it ran great except about half way home I heard an odd misfire . It honestly sounded more like my muffler fell off for a split second . Kept driving as nothing else seemed to oUT of the norm. 2 Corners from my house it did the misfire again honestly sounded liken it was right inside the muffler . Last corner the car almost stalls but keeps going and evens out. I get home and the car idles perfectly fine sitting in park. Put it drive and is fine , could not get it to miss again.

I pulled a few plus to see what they look like . I am crusing at 14.0 on wideband and the car seems to be running great other than the weird misfire.
The car deffinently seems to be running cleaner dosent smell as rich as it used to.

Here are the plugs. Thoughts.......

 

[Aron Gleason]

Looks like it's running a little rich. Might try to get the afr's in the upper 14's to low 15's at cruise. What's your afr's at idle?

 

[Slap Stick]

Regap at .035, also.

 

[ddpsnake]

well i did not know plugs could say something.

 

[Lefty71]

One note to keep in mind.... you can't just drive around, then pull plugs out and get an accurate reading.... You really need to kill engine immediately after a WOT run and then check them. Also, it seems to me anyway, you'll have a hard time getting a perfect burn all the way around the porcelain on any wedge.... it'll always be a little discolored from one side to the other, in my experience.

 

[Ghostrider 67]

Bzzsttxzzztt.....bzzztztxxsttz,,,

 

[Canadian1968]

I wasn't looking for WOT reading . More how the car is running under regular driving conditions . And is there anything that may help me figure out the random miss fire.

 

[Don Frelier]

Sounds like the miss occurred near corners?
Water or debris in the carb?
Random misfire can be rotor phasing or spark scatter inside the cap.
Not saying it's the cause but it can be.
Spark gap at .040 is likely on the low end with HEI.

 

[Canadian1968]

I heard one miss just cruising at about 60k. The two more noticeable were pulling away from a stop. Going to check the inside of the distributor cap and rotor when I get home

 

[BSB67]

One note to keep in mind.... you can't just drive around, then pull plugs out and get an accurate reading.... You really need to kill engine immediately after a WOT run and then check them. Also, it seems to me anyway, you'll have a hard time getting a perfect burn all the way around the porcelain on any wedge.... it'll always be a little discolored from one side to the other, in my experience.

Old plugs, some idling in neutral, some idling in gear, some cruising, some accelerating, some decelerating. You cannot come to any real conclusion, although people seem to think they can.

Also, folks seem to believe that certain AF numbers are what you need to target because of stoichiometry/chemistry. What a chemistry book says and what a 1960 vintage motor/combustion chamber needs are two different things. Absolutly use the AF info as a tuning tool, just don't hang on too tight to some absolute numbers or values. Give the motor what it needs/wants. If you think it's AF related, try moving in both directions.

Think real hard on when the misfire happened. Anything below 2000/2100 is probably in the transition. Were you accelerating or decelerating ever so slightly?

I'm not even 100% certain that your new problem is necessarily from the change you made (but that is where you should absoulty focus, just keep your mind open). Buy new plugs and try them, maybe a step cooler, and think hard about anything else, no matter how small, that you did/touched during the conversion.

 

[moparedtn]

Bzzsttxzzztt.....bzzztztxxsttz,,,

 

[Canadian1968]

Old plugs, some idling in neutral, some idling in gear, some cruising, some accelerating, some decelerating. You cannot come to any real conclusion, although people seem to think they can.

Also, folks seem to believe that certain AF numbers are what you need to target because of stoichiometry/chemistry. What a chemistry book says and what a 1960 vintage motor/combustion chamber needs are two different things. Absolutly use the AF info as a tuning tool, just don't hang on too tight to some absolute numbers or values. Give the motor what it needs/wants. If you think it's AF related, try moving in both directions.

Think real hard on when the misfire happened. Anything below 2000/2100 is probably in the transition. Were you accelerating or decelerating ever so slightly?

I'm not even 100% certain that your new problem is necessarily from the change you made (but that is where you should absoulty focus, just keep your mind open). Buy new plugs and try them, maybe a step cooler, and think hard about anything else, no matter how small, that you did/touched during the conversion.

You raise interesting point about the transition. The misses were basically all at very light throttle 2 for sure on decell and one for sure on accel .

I had adjusted my idle higher. Could be getting into a problem with the transition slot...... hmmmm

 

[Ron H]

well i did not know plugs could say something.

You mean verbally or visually? lol
Old school mechanics read plugs like a book.

 

[RJRENTON]

One note to keep in mind.... you can't just drive around, then pull plugs out and get an accurate reading.... You really need to kill engine immediately after a WOT run and then check them. Also, it seems to me anyway, you'll have a hard time getting a perfect burn all the way around the porcelain on any wedge.... it'll always be a little discolored from one side to the other, in my experience.

Very true, to some extent.....the basic cause is the dark colored side faces the intake valve, where it is "charge cooled" by the incoming fuel mix. AFR devices are a tool that takes an INSTANTANEOUS reading of the %O2 in the exhaust gas. Do you have a sensor in each exhaust stream or just one stream? Due to the the uneven mixture velocity characteristics and mixture densities, usually due to the manifold runner length differences, accounts for the uneven AFR numbers. Perhaps a better method is to use 2 probes and AVERAGE the combined readings over time. But unless one can make in process adjustments, at each desired operating point, the whole process seems futile. Carbs cannot be electronically conttolled (with the exception of GM's M4MEA Quadrajets) like a pulse width modulated EFI, to obtain best AFR. Just my opinion of course.....
BOB RENTON

 

[RJRENTON]

Bzzsttxzzztt.....bzzztztxxsttz,,,

Translate please......what language are you speaking....or thinking in.....or perhaps just noise.....
BOB RENTON

 

[ddpsnake]

.........................................................

 

[MarPar]

Bzzsttxzzztt.....bzzztztxxsttz,,,

 

[Canadian1968]

Very true, to some extent.....the basic cause is the dark colored side faces the intake valve, where it is "charge cooled" by the incoming fuel mix. AFR devices are a tool that takes an INSTANTANEOUS reading of the %O2 in the exhaust gas. Do you have a sensor in each exhaust stream or just one stream? Due to the the uneven mixture velocity characteristics and mixture densities, usually due to the manifold runner length differences, accounts for the uneven AFR numbers. Perhaps a better method is to use 2 probes and AVERAGE the combined readings over time. But unless one can make in process adjustments, at each desired operating point, the whole process seems futile. Carbs cannot be electronically conttolled (with the exception of GM's M4MEA Quadrajets) like a pulse width modulated EFI, to obtain best AFR. Just my opinion of course.....
BOB RENTON

I learned a long time ago that the wide band is not the answer to all the problems. But it is a an amazing diagnostic tool and aid in tuning. I only run one single sensor on driver side bank about 6 after the collector. I did weld a bung into the other side but have never bothered to switch. I use the AEM unit with self calibrating bosch sensor. I forget the exact specs but this thing takes multiple readings per second. The gauge never really sits still , due to the numerous variation in each cylinder that you mentioned ( intake runner, header length, cylinder head ect.... ) But you can get a pretty good idea of whats going on, once you learn to read the gauge and know your motor . I expect a variations of around .2 to .4 during idle, if I consistently see a blip of more than that I can choose to look further into it. And during driving nothing beats the ability to instantly know if you are leaning out or running rich during different throttle inputs. You can then use that info to decided if you need to adjust jets, play with accel pump cams, change springs, the list goes on. I can promise you it would have taken me twice along to get the car to where it is now, with out it.

 

[moparedtn]

I'd be more concerned about going too lean under hard demand myself...
but I ain't no expert.
That's why I'd like to use a wideband eventually to dial in a carburetor:
Run the car down the road, go through the paces watching the meter.
Get back to the shop, make any jet/rod changes, run it again...

 

[RJRENTON]

.........................................................

I thought that is what you meant to say, but were unable to express yourself more accurately, due to a minimal command of the SPOKEN word. You may consider saying: qzyzuz....yyqqxex,rsqqyyg, or something equally profound.....or not....just something to consider....
BOB RENTON