Re: Whats the difference?
I belive the main difference is that the J4C has a 13/16" socket drive, and the JC4 has a 3/4" socket drive. They're both 14mm, 3/8" reach, heat range '4', non-projected nose, and full sized plugs. There's a slight difference in the ground electrode design, but I can't imagine that matters much.<br /><br />Hope this helps!<br /><br />EDIT: If you're planning on using plugs that weren't recommended for your engine, you must check the plugs after running them a bit to make sure they're not too hot or too cool. Both plugs are cheap as dirt, and I never have any trouble finding them in stores myself.
