[673x2]

I have an opportunity to purchase nos AC sparkplugs for my car.Its a 68 ss 396/325. The standard AC plug is a 43n, the plug thats being offered is a c42n (cold plug). Can someone shed some light on the differences.Will it matter if I put in cold vs standard plugs? Any input is welcome.Thanks,Brian

 

[Keith Tedford]

If you are doing a lot of around town driving a 44N works well. I have always run AC 43N plugs in our engines and that is what came in them from the factory. One heat range colder probably wouldn't hurt especially if you are doing much highway driving. Cold plugs don't like city driving and long idles. When I run out of 43N plugs I will be looking for NGK equivalents.

 

[NickeyChevelle]

Back in the day I ran cold Lawn Mower spark plugs in my '70 SS for (street) racing. They worked very well, there was a noticible increase in seat-of-the-pants response. The only problem was the plugs didn't last very long, and not many stores carried 8 of them in stock.

 

[engineguy]

Brian,
The standard plugs will work best in your application. Colder range plugs are only necessary if the compression ratio has been raised and as stated in previous posts, they will not last as long as the standard plugs will.