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Spark Plug evaluation

JohnEngland

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I need a little help if I may get it. I am a beginner at reading plugs. The attached plug was pulled after cruising around. Timing is set at 15 initial and 35 total., The enginge is a 472 stroker with a Quick fuel 780 vacuum secondary carb. Vacuum advance is being used. Hughes cam Lift .571 and .582 lobe sep 110 degrees, duration at 50 degrees is 232-236. Plugs are RC12YC campions gapped at .035. Rev a nator Ignition box. Idles at 850 rpm. 93 octane no alcohol fuel.
The ground strap to me looks lean.
Thanks for any guidance:)

newest.jpg
 
I would say that is not too rich. Possibly lean. How did the car act on your cruise? Did you do any burnouts or anything. Did it cut out, overheat? What jets are in the carb primary side?
 
Drives excellent. It pulls good. It will roast tires.It did not cut out. Drives at180 degrees. Primary Jets 72
 
I would say that you are pretty close then. Somebody else on here will have a more experienced analysis than mine. I remember watching on Nascar, Jack Roush and Robert Yates look at the plugs with those magnifying glasses...I'm not that good.
 
If You want to play with it maybe go up in jet till you see some color. If it was mine I would leave it alone. Find a safe place and do a full hard pass shut it off and coast then pull a plug. Are you running an AFR meter?
 
Are you running stock iron or aftermarket heads? I ask since they aren't the shorter RJ12YC.
 
If You want to play with it maybe go up in jet till you see some color. If it was mine I would leave it alone. Find a safe place and do a full hard pass shut it off and coast then pull a plug. Are you running an AFR meter?
No AFR meter
 
What scares me the most in the ground strap not showing any color and no timing mark . They are new plugs but after 20 miles they should show some marks or maybe not?
 
Which heads? What is the CR? The RC12YC is a fairly hot plug. That looks a tad lean to me, but I have never been good at reading plugs. If it runs good, you're in the park.
 
What scares me the most in the ground strap not showing any color and no timing mark . They are new plugs but after 20 miles they should show some marks or maybe not?
Our unleaded swill makes it tough to see anything on the plugs. Maybe try a colder plug like 66Satellite47 says. Cant hurt.
 
Which heads? What is the CR? The RC12YC is a fairly hot plug. That looks a tad lean to me, but I have never been good at reading plugs. If it runs good, you're in the park.
Agree. I would go two steps colder. The actual fire ring is inside on the porcelain.
 
I see no reason to go to colder plugs. If anything, alum heads need a hotter plug because they conduct heat better than CI & run cooler. If the head runs cooler, a hotter plug is needed to keep the tip temperate between the desired 400-850*C.
 
I see no reason to go to colder plugs. If anything, alum heads need a hotter plug because they conduct heat better than CI & run cooler. If the head runs cooler, a hotter plug is needed to keep the tip temperate between the desired 400-850*C.
You’ll never hurt and engine with a colder plug. If you raise hp thats first thing you need to do. If they foul then you step up. Thats good advice to anyone.
 
True, you will never hurt an engine with colder plugs. But you can certainly cause it to run like crap & lose HP. That is because if too cold, the plug does not burn off the deposits....& it misfires.
You want the hottest, not the coldest, plug that the engine will tolerate that does not cause pre-ign.
If look at the engine specs, they are quite mild; this is a tq engine, not a 900 hp monster. There is no need for a colder plug. You use colder plugs when [a] the engine is at WOT for long periods such as road racing has a power adder. This engine has neither.
 
No, you put in the manufacturers heat range plug, which in my NGK catalog is a '5' heat range.
If the engine use/load changes as per post 16, you go to a colder plug.
 
True, you will never hurt an engine with colder plugs. But you can certainly cause it to run like crap & lose HP. That is because if too cold, the plug does not burn off the deposits....& it misfires.
You want the hottest, not the coldest, plug that the engine will tolerate that does not cause pre-ign.
If look at the engine specs, they are quite mild; this is a tq engine, not a 900 hp monster. There is no need for a colder plug. You use colder plugs when [a] the engine is at WOT for long periods such as road racing has a power adder. This engine has neither.
Perhaps you have not heard of the concept of "charge cooling", where the spark plug electrodes and center electrode insulator are cooled below the auto-ignition point by the incoming fuel mixture's velocity and the latent heat of vaporization principle. In addition, substitution of NON-PROJECTED center electrode spark plugs and insulators and or spark plugs with different alloy electrodes can help solve fouling or preignition issues. In addition what is your definition of "power adder", and the generalization of:
"You want the hottest, not the coldest, plug that the engine will tolerate that does not cause pre-ign" is too vague, without knowing specifics.
BOB RENTON
 
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