sweetnessmonster wrote:
FrugalFreak wrote:
440 All years use
Champion Copper / Spark Plug Part Number: #406 or RV12YC
This is what I picked up and installed today. The parts store didn't have any RV9YCs, and the guy said he hadn't seen that cold of a plug in a while. He was familiar with the confusing situation, and found the RV12YC listed for use in all motorhome 440s. I figure the previous owner had changed to a colder heat range for some reason. I'll pull them and check them after some miles to see how they look. So our rig now has a new cap, rotor, and plugs and it runs great. Now just to see if it will pass smog.
Pinging (pre-ignition/detonation) would be one reason for going to a colder plug. Basically, the sparkplug tip gets hot enough to ignite the fuel/air mixture before the distributor fires that plug ... make sure the timing is on the mark. (Yes, I've seen people install colder plugs to deal with timing that was off ... they should have fixed the problem, not the symptoms.)
