Decode Champion Spark Plug Numbers
Thread Starter
Racer
Joined: Mar 2005
Posts: 294
Likes: 1
From: Racine Wisconsin
Decode Champion Spark Plug Numbers
The recommended plug for my 1973 SB is R44T and the engine performs fine with those installed--no pre-ignition and no fouling. When I asked the local parts shop for "spark plugs," I was given a set of RV17YC. I don't have a brand preference so I purchase them. When I was about to install the Champions, I noticed that the electrodes for the RV17YC extend 1/4" (5 mm) farther into combustion chamber than the R44T. To make this more confusing, Champion recommends the RV19YC for the 1973SB not the RV17YC. The extended electrode would appear to be an improved design provided it does not interfere and retain heat. My questions: Does the extended electrode of the RV17C cause any problems? What would be the appropriate temperature range 17 versus 19?
Race Director
Joined: Apr 2000
Posts: 17,665
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
RV17YC is not correct replacement. It has a projected tip where the R44T doesn't, but more important is the fact that it has a tapered seat where the R44T ( unless there are some other numbers after ) is a gasket plug. Putting those plugs in your motor could ruin it. 
Correct replacement Champion plug is RV12C6 or RV8C.
Correct replacement Champion plug is RV12C6 or RV8C.
Last edited by MotorHead; Jul 20, 2008 at 04:18 PM.
Race Director
Joined: Apr 2000
Posts: 17,665
Likes: 194
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
That is what I thought, but has been a while since I had stock heads. Anyway I have a huge spark plug master cross reference that is telling me R44T is a gasket plug. So disregard any info I gave as I guess this reference is not reliable 
Racer
Joined: Apr 2004
Posts: 370
Likes: 0
New England Events Coordinator
I just spoke to AC Delco, they tell me that the R44 (for the 70 Vert 350/300HP) is no longer available, replace with r45s, "s" stands for extended tip. Is the extended tip an issues for this application?
Race Director
Joined: Nov 2002
Posts: 12,142
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From: Taylor Michigan
Le Mans Master
Joined: Nov 2008
Posts: 5,691
Likes: 12
From: columbus oh
the neat things about comparing champion plugs with ac plugs are the many numbers available for each and every heat range they have....ac stands for albert champion as lore would have it , so he started marketing champion plugs. back in the day, an ac 44 would cross reference with a j 12 champ........you had 44,44r(resistor)44rs(extended tip) 44rsx(serrated tip) and so on. the champs that ended in a y were extended tip. a yc was extended with copper. a u prefix was resistor, the t means tapered plug. sorry for the long run on but i think you have the wrong cross referenced champion to ac plug...jmho
btw,an r44 will not work for an r44t because the t stands for tapered
btw,an r44 will not work for an r44t because the t stands for tapered
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