Correct Spark Plugs - 72 Indian?

[Clyde9]

From: agilek91  (Original Message)
Sent: 9/1/2007 10:31 PM

Hi,

I'm ready to replace the spark plugs in my '72 Indian. I've been reading all of the different ways to deal with the hard to reach left side of the engine. I believe I've worked out a method.

However, I went to a local auto parts store and asked for plugs for a Dodge 413 engine. They gave me champion RN14YC plugs. When I removed the first plug, it was a RN12YC plug. I stopped and decided to contact this group.

I'm just learning about all of this and don't know if these two plugs are interchangeable. What is the difference between the two?



From: denisondc
Sent: 9/1/2007 11:17 PM


I would say they are interchangeable. The different numbers refer to the heat range. I believe the higher number means a 'hotter plug'. I think I have RN12YCs in mine. If the engine had high compression, the hotter plug (RN14YC) would be more likely to reach high enough temperatures to cause 'pinging' or detonation. But the 413 is a very low compression motor, so its unlikely that would ever happen. Having the lower number would be more likely to lead to cold-fouling in a motor that was used for lots of short trips where it didn't get fully warm each time. Also not likely in a motor home. Thats why I think either plug would be fine.