ok i didnt know how the heat ranges ran I didnt know if they ran like 12s thec 11s 10s ect
Yes, down in number is colder.
Normally stock heat ranges for passenger car and light truck engines are 14 and 12. For performance 11 and 9.
Sorta. The higher the compression, the colder the plug, as a general rule. in other words, you don't want a plug that puts a lot of heat into the cylinder head (and combustion chamber) on a high compression engine, like a hot plug would tend to do. Saying the a cold plug is better for a performance engine is a little broad, since a low compression engine CAN also be a performance engine if built for it. In that case, the performance engine would not need a colder than normal plug. It's compresseion dependent. If that makes sense.
You won't notice any difference changing from one brand to another, as long as the heat range is the same. If you run a compression test, you can get a good idea of what plug heat range you should run. Sounds like you should be running whatever plug is correct for the 68-71 340.
You can find old stock ones all over eBay pretty cheap. If you hunt long enough you can get them cheaper than the new ones from rock auto
ok thank you
if you try different searches for champion n10, champion rn10y, etc., you'll get all kinds of different results
