Spark Plug theory!

[Dart_340_Swinger]

Well i have a 318 with a low-end cam, headers, dual, intake holley 650cfm carb! I used to run autolite 65s and switched to Accel 496 plugs! Does anyone know if i should run a colder or hotter plug!
What are the advantages of a:
COLDER PLUG
HOT PLUG
And what should i be careful of!

Also i didn't pick the plugs out the guy at the Speed Shop looked them up for me (This guy is all MOPARS, i trust him)I HOPE!

[toolman]

Spark plug recommendations in a performance book I have says for a stock 318 use Champion N14Y. I had the Performer Package from Edelbrock and I used anything from N9Y up to the N14Y. The coldest N9Y is recommended for racing because it can foul easier with regular street driving. I didn't notice any performance gain or loss with any of them comparing one to another. Although if you ever have any dieseling or pinging, I would stay away from the hotter ones. Which ever you choose, you should be able to look at your old plugs to see if colder or hotter is needed. I think Champion has a brochure on haw to "read" a spark plug. Typically, I check the color. If it is dark brown or black, I go to a hotter plug. If it is White or light brown you can go colder.

[moparking]

I'm not sure about autolite/Accel spark plug heat range numbers, but I can give some advice. You want to run the heat range as high as possible without detonation. This will "burn" deposit off of the plug. The advantage to the lower heat range plugs in a race application is that they will prevent detonation, and allow a more agressive advance curve for more power at the expence of plug longevity. If you try to run too cold a spark plug, they will foul and the car will miss and run like s*#%t. It's better to start out cold and foul a few plugs, than to burn holes in your pistons.

[Christopher]

I ran into the same problem on my 318 a long time ago.I ended up using Champion N-12Y's and they worked great.The N-11-Y's were too cold.

[Stan Cameron]

I agree with moparking.
But the higher compression you have the colder the plug needs to be.

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69 RR 426 4bbl 727 9.88 @ 135 best so far.
79 Lil Red Express.
96 2500 Ram 5.9
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