Spark plug Question which ones NEED HELP

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Sep 13, 2005 | 10:26 AM

triplepower

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Spark plug Question which ones NEED HELP

I have a 91 250 4x4 with a 351 I pulled the plugs and they are champion-RN9YC4 and the book call for champion RV15YC. I just bought the truck and the plugs that were in it(rn9yc) are much bigger around and the threads are like a quarter in longer. Does anyone have any insight, should I just put the new ones in. They just look so much different in thickness and length.

Sep 13, 2005 | 11:06 AM

triplepower

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ok i went on champions web site, and answered my own question, the ones that were in there won't even fit a ford. I don't know what dumb *** put them in. No what do you think putting the new ones in will do for my motor????????

Sep 13, 2005 | 12:27 PM

triplepower

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got it all back together and it is missing all over the place!!!!! I got a haynes manual and I think I got the wiring right to the distributer no I'm at a loss!!!!!
All I did was plugs wires cap and rotor

Sep 13, 2005 | 08:11 PM

TigerDan

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From: The hills of No. Calif.

If you're positive the wiring is correct, pull the plugs and have a look at them. See if they are still gapped correctly. If not, if the gap has closed up, then the plugs are not correct and maybe someone changed the heads. I don't really see it since you describe the old plugs as being longer, but I suppose it's possible.

If all looks okay, then test each plug, you may be suffering from Champion Syndrome. I have seen brand-new Champions dead right out of the box. I had 3 in the same set one time, truck only ran on 5 cylinders till I put the old plugs back in. Switched brands, problem solved.