Spark Plugs: HD 6R12 vs. Champion RA8HC - Not the same!

[Rusticwater]

Over the years I've read that the Champion RA8HC is "the same" as the HD spark plug.

I've always run HD plugs yet decided to try Champion just out of convenience. Tried gapping the new Champion and thought something isn't right. I keep my old spark plugs as a snapshot of engine condition so I grabbed one from the drawer that has about 5K miles on it.

Compare the length of the center electrode on the plugs. The 6R12 plug definitely has a shorter center electrode. Now compare the ground electrodes, notice how the HD one is flat all the way across the entire space above the center electrode.

Not saying the RA8HC won't work...just saying it's definitely not "the same." To me it appears the 6R12 is designed better to handle a wide gap.
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[Ohio HD]

I have no idea who makes HD plugs, but I do know that OEM's will give specifications, characteristics and parameters to the company that makes their product. So still, Champion could be making them to an HD specification.

[Thermodyne]

The Harley part looks a little better as far as strap fit, but its got that old fat steel electrode, where as the champion part is a copper core.

Personally I just use iridium's and change them after 30K miles.

The electrodes on them will really worry you.

[Rusticwater]

I have no idea who makes HD plugs, but I do know that OEM's will give specifications, characteristics and parameters to the company that makes their product. So still, Champion could be making them to an HD specification.

As a Buckeye originally from NE Ohio I have nothing but respect for Champion (Toledo), they have always been my go to. I certainly hope they are the OEM supplier to HD, both have been around a long time. 

[Tynker]

Champion has made HD spark plugs, forever. Don't worry about the little difference in the ground strap in your picture, the Champion just has a slightly longer center electrode.

[klammer76]

I have run the Champions for 17 years, never a problem.

[Heinz]

The gap spec on the ra8hc is .022-.028. I'm pretty sure that is narrower than the 6r12.

[smoserx1]

I have never heard that the ra8hc is the exact same plug as the 6r12.  Rather it was a compatible substitute (along with several other brands).  I did use a set long ago and they worked fine.

[Heinz]

The ra8hc came with my S&s 124.

[dirty jim]

Don't know who makes Harley's plugs nowadays, but back in the Shovel Head days it was Autolight. If you held them side by side the porcelain insulators were identical.

[calif phil]

Champion has made HD spark plugs, forever. Don't worry about the little difference in the ground strap in your picture, the Champion just has a slightly longer center electrode.

This!

Champion has made HD plugs probably for 100 years.  The RA8HC work just as good as the HD plug.   

[Rob L]

The S&S 124 I bought came with the Champion plugs

[Propflux01]

I just use NGK.

[No Cents]

I just use NGK.

      me too.   
let's keep it a secret.