Spark Plug Heat Range

[Granny 2]

Which AC plug is the hotter plug, a 42 or a 43?

 

[cruzn57]

plug heat range

In an AC spark plug, the hotter is the larger number,
so 43 is hotter than 42. other brands vary, so this will only apply to AC
good luck
cruzn57

 

[Chuck Leeper]

PLUGZ??

As the numbers get larger, the heat increases. This is due, mostly to the tip being further into the chamber..

I use:
AC CR42ts for hi boost race gas.
CR43ts for the street.

 

[Granny 2]

Thanks

 

[TR Custom Parts]

So which would you use if running high boost on the street with alky? I am using the 43's now and wonder if I should switch to 42's?

 

[Dan Thompson]

This is from GNTTYPE website on a recipe build up.

"... replace the plugs with AC R43TS plugs gapped at 0.035 for 13 to 14 second cars and AC R42TS plugs gapped for 0.035" for 12 second and faster cars."

 

[Blk Bty]

Use the CR plugs. They are for commercial vehicles and they have a bigger electrode. I think they help handle the boost better, less knock,IMO. Picked up 6 at Champion Auto for $10. Good investment.