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What do you think reading this plug?

JG71B

JG71B

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Stock 78 400 motor, Seems to run good drive good but what's up with these plugs? They all look wet and dark like this. I've never been good at tuning carbs (running an eddy 1406), is this a rich condition? Need a hotter plug maybe? I really don't think it's oil as it's a low mile motor and it doesn't blow smoke at all. Appreciate any help !
20210731_235450.jpg
 
400 have exh manifolds? Passenger side heat riser stuck closed (check it) could be 1; if Champion plug, TRASH em!!! Try Autolites: Background: 77 Cordoba 400 Lean Burn with 4bbl; same issues back in 80s: Champion took 8 plug ranges made 1 in middle range: heat riser valve was stuck closed, FORTUNATELY, found LB expert in New London CT in 1987 who straightened it out & educated me. GOOD LUCK
 
Open up the air needle screw's a half turn. See what that dose. That should lean it up.
 
Looks like it has been on the choke a lot and not driven much.
That said ensure the choke is fully open when engine is warm.
I haven't used Champions for ages but the last time I did they didn't work well.
Give er the old Italian tune up and flog that thing.
 
Slap Stick said:
Looks like it has been on the choke a lot and not driven much.
That said ensure the choke is fully open when engine is warm.
I haven't used Champions for ages but the last time I did they didn't work well.
Give er the old Italian tune up and flog that thing.
Click to expand...
Plan on 86in the Champions today trying something else. Choke open full
 
I would lean that out for sure. Edelbrock has a chart to do that. Pretty simple.
 
Frank Mopar said:
I would lean that out for sure. Edelbrock has a chart to do that. Pretty simple.
Click to expand...
I have the chart from the carb manual I been looking at. Trying what I can before I start diggin in. Been a minute since using Champions. Didnt realize how nobody cares for them these days. As a lot of things, not like they used to be. Anyone use the ACCEL plugs?
 
Some better shots of the plug would be great. Looks way too rich. You didn’t say anything about the application except stock 400 with an edelbrock carb. Adapter on a TQ intake? Car or Truck?

Everyone is quick to have you dump the champion plugs but this plug is the correct heat range for that motor stock and they were the OEM plug for decades in new Chrysler products.

How do the rest of the plugs look? What ignition system? Are you using oil?

Cliff Ramsdell

A close up like this is a better view. This plug says it’s a little rich at idle and has a couple degrees too much total timing. This is from a 68 372” 340 with stock manifolds and an edelbrock. Champion RN9YC plugs.

BE51329E-5AC9-4508-B301-3C8B1EC971C1.jpeg
 
Edelbrock Performer carb/intake, Cloyes double roller and Hooker Comps. Internals untouched otherwise. (Dont mind the pie tin)
20210723_151012.jpg
 
Last edited:
looks like its running rich to me . What were the driving conditions before the plugs were pulled??? Long cruises?? OR short drive. Kinda of looks like its running cold to??

Thats why I ask what the drive was like before you pulled the plugs, if the engine never got fully warmed and its running rich as well ?
 
Mostly sit and idle since just getting it all together. Farthest is around the block 1/2 mile or so!? Never drove it before, just heard it run then pulled it. It seems ok driving. Responsive, smooth, no stumbling or hesitation. I really just pulled a couple to see what they looked like and was surprised. Temp typically 185 to 190. When its 90 out or hotter around 190 or so
 
Inside the back cover on older Chilton's manuals is a Spark Plug Troubleshooting Chart complete with photos. I haven't bought a Chilton's in years so am not sure if newer editions still have them, but it sure is handy.
 
That is oil fouled rich would be sooty and have deposits on ceramic.
High mile motor?
 
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