Spark My Plug

[brodie123]

Hi All;

I have a question about spark plug selection - specifically the heat range.

I'f I'm trying to burn off carbon a little better, do I go up or down in heat range?

i.e. The engine (Merc 4.1L L6) calls for AC Delco MR42TS, am I better or worse with AC Delco MR43TS (heat range of 3 vs 2)

With thanks.

 

[Scott Danforth]

the MR42TS will be a bit harder to find than the 43. I would try switching. if you have run-on switch back.

carbon usually means your running rich.

 

[brodie123]

So I assume then that the 3 actually gets hotter?

I wasn't sure if the higher # meant the plug gets hotter or could tolerate more heat.

 

[brodie123]

After some light reading, I believe that the hotter (lower #) spark plug would foul more easier than a colder (higher #) spark plug but the colder (higher #) could cause run on because the tip is hot.

Do I have this right?