Spark Plug Confusion

[a_disalvo]

I'm not the sharpest knife in the draw, but I know when I don't know or understand something!!! I was using Champion RN12YC spark plugs in my shovelhead. I decided to try Autolite, and their cross reference is a 4265. I than looked at NGK, BPR5ES-11, also cross referenced as a Champion RN12YC. Now here is the weird part!! All 3 plugs have different length electrodes and porcelain, Champion being the longest, than NGK, and Autolite's electrode barely goes past the end of the plug! How can 3 plugs of different lengths cross reference as substitutes for each other with the same heat range? I don't get it!!! Frank

[jamnut]

I really can't answer your question as to why the difference but I have used all three in my 92" stroker shovel and never noticed any difference performance wise. I usually use the 4265 autolites with no problems. Champions work fine as well.

[smoserx1]

I always thought the porcelain was what governed the heat range, but it might be a combination of the porcelain length and "fatness" as mass of a substance is one of the parameters in heat transfer, at least in physics 101.

[Hossamania]

How about the distance or length from the base of the threads to the tip of the electrode and grounding strap? Are they the same length?

[a_disalvo]

No Hoss, they are all different!!! That's what caught my attention. They are the same from the shoulder where the plug seats into the head to the end of the tread. From the end of the tread to the end of the electrode they are all different!

[Hossamania]

That would cause some concern for me. I guess I would get the one that matches closest to the stock dimensions.
Having said that, I run the Autolites in my '01 and use them in friends Evos as well. The '12 gets stock plugs, just to avoid any ignition problems with the anti-knock sensors.

[mr. pitts]

Why not email them all for a definitive answer?

[K4FXD]

IIRC, the extended tip plugs are supposed to perform better than the normal plugs.

I believe they were marketed as having a wider heat range.

Supposedly the manufacturer could design a hot tip, that reduced fouling, but have it act like a colder plug. The incoming air fuel mixture cools the tip keeping it from becoming too hot.

So each plug you mention uses a different way to make the proper heat range for the engine. All are compatible in the application.

[a_disalvo]

That makes sense, thanks for your input!!!

[dirty jim]

Back in the '60's and '70's Harley was in bed with Ford. Harley plugs were re-branded Autolites.

[Boe Cole]

Had a Maico dirt bike when I was living in Germany that I used to race motorcross.  Had major problems with plugs fouling.  Used a cross reference for the required Bosch plugs and got some Champions.  Never fouled a plug after that.

Moral of the story - not all cross references are the same.  Just have to find what works best for your bike.  If the plugs are reading right, life is good and stay with them.

[1workinman]

  Years ago many years ago I helped a friend with his Camaro . I did wrenching he drove it . We took it to San Antonio to the nationals and we parked by a fellow that had a record holding car it was I think a hemi cuda ,  The Camaro had a aluminum 427, glide ect . It has a 1050 dominator on it . I had problems with the car and the fellow with the car asked what king of plugs , I said champions and he laughed and said go get a set of autolight plugs and when you win screw in the champion plugs . It helped a lot I never forgot . That and a 2.5 power valve lol    The extended plugs I was told a long time ago run hotter at slow speeds and get cooled by the charge at high speeds hope that Is correct

[No Cents]

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[a_disalvo]

I can remember when Autolite was the only spark plug manufacturer that gave a warranty on their plugs! Now, today, the box states " MADE IN CHINA" !!! Frank

[1workinman]

I prefer Bosh , NGK , Autolite , Ac Delco . My favorite use for a champion was to hook it on my line and drop it in the water to un fowl my lure . That was about it lol 

[a_disalvo]

Just for S##ts and giggles I priced the NGK Iridium~~~~~~ $13.00 each. Not for me!!!!