what spark plugs

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moparraceman

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have a 1974 360 duster mild cam, alum intake , 625 carter carb ,headers, what spark plugs do you run? auto light or champion ? thanks
 
I have run Champion RN12YC's and can't complain one bit. Recently I ended up with NGK (BPR5ES) because my local parts house couldn't get the champions. It may just be me, but I swear the car idles better with the NGK.
I am not saying it's because the NGK is a better plug, but my engine combo seems to be happier with it. You may want to try a few flavors of plug to see what your combo likes.
 
zakimodo said:
I have run Champion RN12YC's and can't complain one bit. Recently I ended up with NGK (BPR5ES) because my local parts house couldn't get the champions. It may just be me, but I swear the car idles better with the NGK.
I am not saying it's because the NGK is a better plug, but my engine combo seems to be happier with it. You may want to try a few flavors of plug to see what your combo likes.
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The 12 is probably one range too cold. Go to a 14 and see that happens.
 
yellow rose said:
The 12 is probably one range too cold. Go to a 14 and see that happens.
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I have run the 14's and had issues with the engine wanting to "diesel" when shutting it off. That is what led me to the 12's.

All of that said, lots of fine-tuning has taken place since then. Might be worth trying them again.
 
zakimodo said:
I have run the 14's and had issues with the engine wanting to "diesel" when shutting it off. That is what led me to the 12's.

All of that said, lots of fine-tuning has taken place since then. Might be worth trying them again.
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Interesting. What is your compression ratio?
 
I went from champ 12’s to accel plugs. Difference between night and day.
 
I have tried in the past year on my 30 over 340 with headers, exhaust, camshaft etc... champion RN12C, Autolite equivalent, and NGK equivalent plugs... I am no mopar genius so take this with a grain of salt...

With all the different brands of plugs and in no particular order... My car starts right up, idles, drives fast, drives slow, stops, and turns off...

A couple of times I even mismatched the plugs and had the same results. Good luck with your search.
 
I run the NGK's as well. You should always check the resistance of the plugs to make sure they are good. I've had to go back to the parts store 3 times to get a good set of 8 and in the end I just took my multimeter with me to make sure I left with good ones. Spark plugs have 2 joints that can fail and create problems of high resistance so a good one will measure no more than 0.08 Ohms and lower.

You would be amazed at how many actually come out of the box with issues.
 
You could pretty much run any of the more popular brands out there and have good results, it’s just a matter of getting the tune and heat range dialed in IMO.
 
Bought a new set of plugs to replace in one of the bracket cars a while back....found out i had 3 different brands of plugs in it....autolite...ngk and champion...

New set of all the same did not run any faster either
 
ch1ll said:
I went from champ 12’s to accel plugs. Difference between night and day.
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I should say this was with a stock 318, 340 x heads and a wild crower cam of unknown specs(swap meet cheapie). the motor had very low compression. It ran 14.06 at 90mph in the quarter with 4.56 gears and a spool. the thing is it hit 90 at the eighth mile mark and would not accelerate any more. I knew I should have milled those heads before I put that motor together but didnt.
 
zakimodo said:
I dont know for certain (a younger,dumber, impatient me didn't take the time to check). 78 block w/ flat top pistons. 360 heads shaved .040. If I remember right the guestimation was 9ish:1
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Thanks. For that CR the 12 should be the coldest plug to use. If you are running a 195 thermostat that affects run on and things like that. The higher the coolant temp the more sensitive the engine is detonation, run on, timing curve and such.
 
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