Spark plugs condition

[Cisco82]

Hi fellows
After about 700 miles i d like to share with you the condition of my spark plugs .. they seem good o me what about your opinion?
The truck runs good , sometimes it struggles a bit if I go just with a bit of throttle opened but if I open a bit more it goes well without hesitation.
Thanks
Cheers

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[svramselaar]

hi

for me if the timing is ok it is a bit lean or the wrong heat plug
normal i say for the color it must be coffee with milk

george

[rickf]

I also say a bit lean but I cannot see the insulator to see where the heat ring is forming. What plugs are they? Do you have the timing set right on the line?

[acudanut]

I also say a bit lean but I cannot see the insulator to see where the heat ring is forming. What plugs are they? Do you have the timing set right on the line?

Yeah, What type of plugs are those ???

[Lou]

That looks like a civi plug in a military adapter. Agree it looks a little lean, maybe the plug is the wrong heat range?

[Cisco82]

HI
The plugs are champion rj6c , the same suggests by the vendor where I bought the spark plug adaptor.
I was thinking the mix was a bit lean as you suggest, I ll increase the mix (unscrew mixture screw) of about half turn and i ll check the results
How many miles do you think it is necessary to wait before checking again the plugs?

[Cobra5]

Here's a thread from a few years back on the other forum. Looks like champion J-8 or AC-45. https://forums.g503.com/viewtopic.php?f=14&t=303504

[rickf]

HI
The plugs are champion rj6c , the same suggests by the vendor where I bought the spark plug adaptor.
I was thinking the mix was a bit lean as you suggest, I ll increase the mix (unscrew mixture screw) of about half turn and i ll check the results
How many miles do you think it is necessary to wait before checking again the plugs?

It all depends on the type of driving you are doing. If you are driving 50-60 miles at highway speed then one trip and check the plugs immediately after the trip. If you are driving around town then basically you would want to check them after a normal day of driving around. This will tell you if you are set for that type of driving. Keep in mind that the only mixture setting on these carbs is the idle mixture. This will carry over to the midrange but once at full road speed it is all through the main jet, the very minor bit added from the idle mixture makes little to no difference at that speed. You need to look at the heat ring on the insulator and see where it is, if it is up close to the tip then the plug is too cold but in your case I am betting it is down near the bottom. Are you by any chance using Never Seize on the plug threads? If you are that will screw up the heat transfer of the plug big time!

[Cisco82]

After 1 day driving in the town/highway about 30 Miles

I ve increased half turn the mixture screw and the idle consequently. The only results seems to be increase of carbon on the top.

I don't use copper on the plug screw

Any feedback?

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[rickf]

Ok, I have to run out for a couple hours but I will get back to you when I get home. Here is something for you to look at in the meantime. Plug reading is a complex science. It is best done at a track and done a wide open throttle with the engine cut at the end of a run and put in neutral. Then the plugs are checked. This will tell you if the main jets are correct, the timing is correct, advance is correct. That is the easy part, checking plugs for around town driving is tough. And changing anything when you have a basically non adjustable carb does not help. Just looking at what you have, Myself, I would just go down one heat range on the plug and see what that looks like. What you have is perfectly acceptable and a bit on the idle rich side which is good for eliminating the M-151 flat spot so do not change the carb if it is running good.

http://www.4secondsflat.com/Spark_plug_reading.html

[rickf]

Ok, Just got back and took a better look at the pics and I back off what I said about the adjustments. I would go back on the adjustment you made and leave it alone based on what I see from the second set of pics. there is a substantial increase of carbon on the plug tip and base in the second pics. The first pics show carbon on the base but lean on the electrode which is usually an indication of advanced timing or hot plug range. The original pic does not look all that bad though so I would leave it alone and if you get the chance to do so, take it out on the road and run 50-55 mph and then just shut it off in a safe place and coast to the side and pull a couple plugs and take pictures of them. This will give a much better idea of what is going on, if the base of the plug cleans up then it is just fine. Those adapters can change the heat range of a plug due to the extended path the heat has to take to dissipate through to the head.

[Cisco82]

Back to the previous setting and you can see the result after 50 miles highway.. more or less the same of the first one.

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[rickf]

That is just fine for a 70 year old design engine, quite good as a matter of fact.
With these engines you need to follow the tune up procedure to the letter and they will run great. If you try to improvise (set timing by ear) you will have problems. Maybe not right away but they will crop up. Timing has to be right on the mark, valves have to be right, distributor timing advance has to be working correctly and if you are running points they need to be set correctly. Last thing to check after all of the other stuff is done is the carburetor.