Spark Plug Heat Range

I know that is something that is not discussed much here so I thought I'd bring it up. I'd like to hear everyone's opinion and practical experience as well as share my own.

My first true experience with the wrong heat range was when I added a 150 shot of N2O to a Ford I built when I was 18 (OK fine, Flame on peckerheads, but this is how experience is gained, lol!). Anyway, I couldn't understand what the little "specks" were on the center electrode insulator when I'd pull a plug after a nitrous run. needless to say, I blew a head gasket shortly thereafter and had to pull the heads. When I did, I noticed that one edge of a few of the pistons looked like it was chewed by a small mouse.

This being the early 80's and widespread use of nitrous was fairly rare and there being no internet as we know it now, I figured it was due to too much advance and backed off 4 degrees. Went back to the strip and promplty comprimised another head gasket. I limped back home with a couple jugs of water and changed the gasket again. The chewing was worse and I had a three or four (my memory fails me, lol!) cracked plug insulators.

I called NOS, and they said "Drop your heat range 2 numbers". End of problems but I still had to re-piston the ford.

So, this being my experience I thought I'd also add what Autolite says about heat range:

Heat range

The term spark plug heat range refers to the speed with which the plug can transfer heat from the combustion chamber to the engine head. Whether the plug is to be installed in a boat, lawnmower or racecar, it has been found the optimum combustion chamber temperature for gasoline engines is between 500
Author: admin