spark plugs used in a 440 CID

[jimbo36]

What are you 440 owners using for spark plugs. My research points to champion RJ14YC. Thoughts??

[captainmaniac]

I have 360's. I used to use RN9YC, but a year ago a mechanic told me I should be using RN12YC....

Also just found this http://www.marineengine.com/parts/champ ... guide.html, which backs up the mechanic's view! Suggestion is that RJ14YC is right for you.

[mikeandanne]

Jim, the stock plug for a 440 was the champion 12 heat range...now in my opinion if you run the boat with the hull in the water at lets say 1500 to 1700 rpm then the 14 heat range will probably be ok ....but if you are going to beat on it then run the colder plug ( the 12)...will suck some heat out of the chamber...thats all I got buddy..

One more thing this all depends on the engines being good ( no oil burn and clean carbs)

[jimbo36]

Thank you for your replies. Mike, the carbs were professionally rebuilt, less than 20 hours on them. They were swapped from my 400's I replaced last fall. My research says the RJ14YC application is for 2 BBL carbs and the 12's for the 4 BBL (can't imagine 2BBL on a big block 440) Anyway, I pulled J6C plugs?? from the port engine and installed the RJ14YC's. The J6C plugs were carbon coated. I can't figure why they were even there. They are used on some 2 stroke outboards and farm equipment. Go figure. Engine runs better in the boathouse. I expect to go for a run on Saturday. I have fixed a couple of issues with the repower. Just trying to stop a small heat exchanger end cap leak. Starboard engine leaked oil on my 6 hour shakedown last week. Just an oil pressure sending unit, got lucky.

[mikeandanne]

Jim , that 6 plug is just a very cold version of the 12, that would explain the carboned appearance, not sure what they were after there, anyway good to see all is well.