Champion Plug question...

[i386]

Guy at the parts house gave me a pair of CJ8 plugs. Everything else I'm reading says use J4C.

I have not taken them out of the package. What's the difference?

 

[Paul Moir]

Re: Champion Plug question...

If you look up the recommended plug for your engine in the Champion book, it says J8C. If you look it up in the BRP reference you find it should be J4C. Now you have a CJ8. Here's the differences:

J4C - correct plug. J=3/8" threaded section, 4 heat range, C Copper Plus design (regular)

J8C - Incorrect plug. Heat range 8 far too hot.

CJ8 - Incorrect plug. "Shorty" version of the J8C.

The plug's porcelain insulation needs to get up to a certain temperature to burn off carbon (to prevent fouling). But if it's too hot, it'll cause the fuel/air being compressed in the cylinder to pre-ignite. The resulting misfire drives up cylinder temperatures causing the piston to melt.
The "heat range" is a code for how hot the insulator is supposed to get. Different engines need different "heat range" plugs. 8 is far too hot for a 33hp and it's use will result in sever engine damage.

 

[i386]

Re: Champion Plug question...

Thanks! Now I'm armed to defend myself if "bubba" at the parts house tells me they are the same when I take them back! 8)

 

[F_R]

Re: Champion Plug question...

See item # 190034046433 on e-bay

 

[Paul Moir]

Re: Champion Plug question...

I don't think he did a bad job. Looked up the motor in the champion book, and then found a reasonable substitute since he didn't have the J8C. The big problem is that damn Champion book.

Not that any other plug manufacturer's are much better. Always go with the engine manufacturer's recommendation.

EDIT: J4C plugs are available easily. You do not "have" to use J6C. The difference between JnC plugs and JnJ is that the ground electrode on the JnJ plugs was filed back until the centre electrode was only half covered. Apparently that helped reduced fouling. It doesn't seem to do much to me, but if you really wanted to you can turn your J4C into a J4J very easily. Perhaps it's all unnecessary because of TC-W3.
The long and short of it is, there's no need to go buying overpriced "vintage" plugs. Get the Champions BRP currently recommends.

 

[i386]

Re: Champion Plug question...

Well, all he had to go on was the plug I gave him. It was an Autolite 2976 which is what was in the engine when I got it.

 

[i386]

Re: Champion Plug question...

This is a done deal.

I went back and exchanged them for J4C. They even say marine on the package. He didn't give me any trouble either.

Thanks for the tip about the heat range. I knew it mattered, but I didn't know you could cause damage by using the wrong one. I just figured it would run like crap.

I hope all my patience and double checking everything pays off.