Reading My Spark Plugs

[glrestomod]

Hello everyone! I’m part of the way through the advice given to me in a previous thread to try and solve a miss in the 1970 383 engine in my 1969 Dodge Charger. I’m now to the part where I check the plugs to see if they are fouled.

Below are pics of the even cylinders in one pic and the odd cylinders together in another. I have three different pics for each four plugs (6 total pics). Do they seem fouled or does anything look problematic? I’m new to learning how these things work (and loving it!) but have a long way to go and appreciate everyone’s input! They should be high resolution so you can zoom in if needed.

 

[glrestomod]

Hello everyone! I’m part of the way through the advice given to me in a previous thread to try and solve a miss in the 1970 383 engine in my 1969 Dodge Charger. I’m now to the part where I check the plugs to see if they are fouled.

Below are pics of the even cylinders in one pic and the odd cylinders together in another. I have three different pics for each four plugs (6 total pics). Do they seem fouled or does anything look problematic? I’m new to learning how these things work (and loving it!) but have a long way to go and appreciate everyone’s input! They should be high resolution so you can zoom in if needed.

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Here are the odd cylinders:

 

[BeepBeepRR]

Here is a chart to help you Identify the problem. Yours look to be in the hot or lean condition. Lean would mean you need more fuel.

 

[oldbee]

Couple jet sizes bigger?

 

[glrestomod]

Here is a chart to help you Identify the problem. Yours look to be in the hot or lean condition. Lean would mean you need more fuel.

View attachment 1649779

How do I fix “hot?” Higher heat rating on the spark plug I assume? Also, as for the lean condition, we just upgraded from a 600 cfm Holley (that was old and already been rebuilt) to a brand new Edelbrock AVS2 650 cfm. Hoping this helps the lean problem. Still trying to solve a miss in the engine that gets worse as the car heats up to operating temperature. Thought it might be a plug. Doing a compression test this evening. Thanks for the chart (I saved it to my phone for future reference) and the help!

 

[glrestomod]

Couple jet sizes bigger?

I now have a larger cfm carburetor on the car, went from a 600cfm to a 650 cfm. Hopefully that will help with the lean condition. Thanks for the help!

 

[Geoff 2]

[1] Carb size has NOTHING to do with a lean condition
[2] You could fit a lawn mower carb.....& it could be rich.
[3] Congrats on the Edel carb, a great choice.
[4] Reading spark plugs for heat range is useless, unless it is done under certain conditions.
[5] Get some NGK BP5S plugs. They are the correct plugs for THAT engine.
[6] Your misfire could be plug. That is why it is best to replace them, to rule out a faulty plug.
[7] Is the engine stock or modified?

 

[Bee1971]

Looking at the base ring and ground electrode - Pictures when you download with this website do not show up as high resolution so that makes things difficult

Anyways I don’t see an lean condition at all

 

[glrestomod]

[1] Carb size has NOTHING to do with a lean condition
[2] You could fit a lawn mower carb.....& it could be rich.
[3] Congrats on the Edel carb, a great choice.
[4] Reading spark plugs for heat range is useless, unless it is done under certain conditions.
[5] Get some NGK BP5S plugs. They are the correct plugs for THAT engine.
[6] Your misfire could be plug. That is why it is best to replace them, to rule out a faulty plug.
[7] Is the engine stock or modified?

Thanks for that info, VERY helpful! I found some Autolite copper spark plugs on sale (40% off) and gapped them to factory spec (0.035) and replaced them and I still have that stubborn miss.

 

[glrestomod]

Looking at the base ring and ground electrode - Pictures when you download with this website do not show up as high resolution so that makes things difficult

Anyways I don’t see an lean condition at all

Sorry, I uploaded them at 1920x1080 but it automatically downgraded the resolution. Maybe uploading them all at once caused the problem? Thanks for the input and the help!

 

[RJRENTON]

Here are the odd cylinders:

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Personally, your issue appears to be a MIXTURE DISTRIBUTION problem rather than a spark plug heat range, Mixture distribution can be corrected by stagger jetting and port/manifold matching By the markings these plugs appear to be Champion RJ-14YC??? Autolite AP-85 or AC R44S would be an equivalent...NGK plugs are good, but not the panacea as described by others Each manufacturer has plugs with different firing end configurations...consider trying a different configuration. I use CHAMPION UJ-11G or CHAMPION HO-8A, both are platinum tip NON PROJECTED FIRING END configuration, gapped @ 0.032" and are 3/8" reach (same as the ones shown in your pix). My engine/car is a '70 GTX, RS23V0A******, with the original aluminum manifold and #'s matching HOLLY carbs. I believe that the normal firing end configuration makes them less susceptible to mixture variations. You DO NOT HAVE TO FOLLOW THE "RECOMMENDATIONS" BY THE MANUFACTURER or buddy.....experiment......just my opinion of course.......
BOB RENTON

 

[glrestomod]

Personally, your issue appears to be a MIXTURE DISTRIBUTION problem rather than a spark plug heat range, Mixture distribution can be corrected by stagger jetting and port/manifold matching By the markings these plugs appear to be Champion RJ-14YC??? Autolite AP-85 or AC R44S would be an equivalent...NGK plugs are good, but not the panacea as described by others Each manufacturer has plugs with different firing end configurations...consider trying a different configuration. I use CHAMPION UJ-11G or CHAMPION HO-8A, both are platinum tip NON PROJECTED FIRING END configuration, gapped @ 0.032" and are 3/8" reach (same as the ones shown in your pix). My engine/car is a '70 GTX, RS23V0A******, with the original aluminum manifold and #'s matching HOLLY carbs. I believe that the normal firing end configuration makes them less susceptible to mixture variations. You DO NOT HAVE TO FOLLOW THE "RECOMMENDATIONS" BY THE MANUFACTURER or buddy.....experiment......just my opinion of course.......
BOB RENTON

Thank you! Those plugs pictured are from my previous carburetor. I’ve since replaced the carb and replaced the Champion plugs with the Autolites, as I got them for 40% off! I appreciate the help and your feedback!

 

[Geoff 2]

The trouble is......a misfire can be sooo many things. Easy to fix/change things like spark plugs is a good idea.
But you could have burned/bent valves, wiped cam lobes, broken v/spring, leaking intake gasket etc

 

[glrestomod]

The trouble is......a misfire can be sooo many things. Easy to fix/change things like spark plugs is a good idea.
But you could have burned/bent valves, wiped cam lobes, broken v/spring, leaking intake gasket etc

That's what I'm finding out, it is very difficult to diagnose seeing that I'm new to all of the mechanical stuff. However, everyone here has been so helpful. I have a checklist of things to get to. Definitely going to do a compression test soon (just got a new compression testing kit) and a mechanic friend is going to help me out. There's no smoke or anything from the exhaust, but there is a slight pinging sound that I can feel when it idles and when I drive it. Other than that issue, it starts up faster than a new car! Just hoping to trace it out and get it resolved. The engine was rebuilt in the early 2000's and doesn't have even 5000 miles on it since then, but it sat from 2013 to 2023 due to a near fire. Just got it running last summer and been trying to sort it out ever since (put over 1000 miles on him since last summer).

 

[NoCar2023]

Also need to check the vacuum.

 

[glrestomod]

Also need to check the vacuum.
View attachment 1651342

Thank you for this! I tried to tune the carb with a vacuum gauge, the highest reading was 18 when I turned both idle mixture screws. The needle would hold steady, then slightly bounce, then be steady, then slightly bounce. Maybe a sticky valve?

 

[NoCar2023]

"the highest reading was 18 when I turned both idle mixture screws"

When you turned them all the way in?

 

[glrestomod]

"the highest reading was 18 when I turned both idle mixture screws"

When you turned them all the way in?

No, I'm sorry, I turned them in until vacuum dropped and turned them out until vacuum dropped and then set them where it was the highest starting with the driver's side idle mixture screw on the new Edelbrock AVS2 carb. That highest reading was 18.

 

[NoCar2023]

No, I'm sorry, I turned them in until vacuum dropped and turned them out until vacuum dropped and then set them where it was the highest starting with the driver's side idle mixture screw on the new Edelbrock AVS2 carb. That highest reading was 18.

Sounds like you're pretty close.
Is the "miss" only at idle?
How does it perform on the road?

 

[glrestomod]

Sounds like you're pretty close.
Is the "miss" only at idle?
How does it perform on the road?

Not just at idle, at idle under load and when driving it unfortunately. Before the new carb it would be worse once up to operating temperature (still does that) but it would be so bad it would want to die it would be so rough.