Cold Spark Plugs Vs. Hot Spark Plugs - Third Generation F-Body Message Boards

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Cold Spark Plugs Vs. Hot Spark Plugs

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Old 10-26-2000, 12:01 AM   #1
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Cold Spark Plugs Vs. Hot Spark Plugs

I am sure this question comes up a lot. But i need to know, what the differences are between the two. Right now im running accel u groove plugs with sucess. But the are the equivilent to a R45s AC plug. So I went and bought some R43s plugs. I want know what to expect. I have mallory promaster coil, accel cap rotor, plug wires, headers, edelbrock performer rpm intake and holley 600cfm 4bbl. If any of that makes a difference. And if it makes a difference in performance, where will it be like top end or bottom end.
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Old 10-26-2000, 10:51 AM   #2
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The "path" the heat takes inside the spark plug is different for hot & cold plugs.

For a cold plug, the heat path is shorter (more direct) from the center electrode to the head. Heat gets sucked into the engine's head quickly.

For a warm plug, the heat path is longer inside the plug, which keeps the plug hotter. I had a website with a great diagram of this, but lost it- anyone know what site that was?

-Tom P (Hot rodded 1986 Firebird 2.8l) from message boards
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Old 10-26-2000, 11:42 AM   #3
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A cooler plug will allow more ignition timing under heavy loads without detonation, especially in a high-compression motor, since the plug is one of the hottest things in the cylinder. A hotter plug will run cleaner longer, and will fire better at medium to high RPM under light load (cruising). Just as a general guide, hotter plugs usually go in lower-compresion, lower-performance motors. There's no "magic number" though; every motor combo is different. You will probably notice no difference in performance or longevity with the change you are making.

"So many Mustangs, so little time..."
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