Spark plug testing ------Part 2

[Bruce B.]

Ok so the testing is going well, now I need some other information concerning heat ranges.

What physical characteristics are used to produce plugs of different heat ranges?

In particular I am interested in AC 43, AC 44, AC 45 and AC 46 plugs.

Thanks in advance.

[William F.]

Re: Spark plug testing ------Part 2

Size of insulator, biggest thing. Reach into combustion chamber has some influence.

[Paul O.]

Re: Spark plug testing ------Part 2

Bruce

The smaller in length the insulator down by the tip is usually the cooler plug the larger or longer is the hotter plug.

[Dale M.]

Re: Spark plug testing ------Part 2

What spark plug heat range would be best for a car for Judging? I assume you want a hotter plug for ease of starting? Is the spark plug heat range every Judged?

Paul, when you reference smaller is that the diameter or thickness of the insulator or the lenght or how much of the electrode extends out of the insulator?

[Paul O.]

Re: Spark plug testing ------Part 2

Dale

In general a hotter plug would be better for cruising around town or during judging for frequent starts and idling. A cooler plug maybe best for long distance cruising at a constant highway speed. As I stated it is the amount or length of insulator that is exposed to the combustion chamber. The more insulator exposed the hotter the plug less the cooler. The insulator prevents the electrical charge from jumping the gap at the side wall of the plug or until it get to the electrode tip.

[Dale M.]

Re: Spark plug testing ------Part 2

Paul, Thanks. I guess I have just gapped and put plugs into the engines without really examining and studing them much. Its somwhat confuing between the heat range and the extended plug, like the S (45S) vs a 45. That seems to just make it a hotter. We used internal electrodes, where the electrode came in from the side in my racing days. It was claimed that our high compression would mast the electrodes together. I believe we used a 43 heat range, but it did not take long to foul these plugs and it was hard starting. Luckly most of the time we were able to push start our car and with our vertex mag that put out a hot spark it always started. Again, thanks for the additional information.