looks like the RN12YC is called out. I assume the next heat range down would be the RN9YC?
What Champion Plug ru Using in you 340?
- Thread starter 340inabbody
- Start date
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N9Y
It depends on what year and compression I believe.
I don't think so...
Well my block is a 73 running J heads with TRW 12:1 pistons. Compression is a little high on pump gas as it’s not stock so I want to go with one heat range from stock. Which I believe to be rn9yc or n9y not sure of the difference.
When you go to Champions ******* web site they use different part numbers like 405 for some dam reason.
Then you go to technical help they have no heat range charts or anything but they do show you how to change oil!
Dam retards over there or maybe someone can prove me wrong and show that Im the retard.
When you go to Champions ******* web site they use different part numbers like 405 for some dam reason.
Then you go to technical help they have no heat range charts or anything but they do show you how to change oil!
Dam retards over there or maybe someone can prove me wrong and show that Im the retard.
With all that compression, run 9's beat on it and read the plugs. They will probably be too cold. That should tell you if they are too cold or not. Many plug reading threads here on the site.
For instance, a 73 340 calls for a 14 where a 68 340 calls for a 12. I don't think any used a 9.
Fast340cuda
Well-Known Member
I ran the RN9YC’s in my 340 when I had cast iron heads as my local speed shop told me that they were the next step down from the 12’s on the heat range.
For what it’s worth, a few years back I had a few champion plugs lose the insulator around the electrode so I have switched over to NGK plugs and have not had any issues since.
For what it’s worth, a few years back I had a few champion plugs lose the insulator around the electrode so I have switched over to NGK plugs and have not had any issues since.
mygasser
Well-Known Member
Well back in 71 that epa mandate changed compression across the board. My 71 454 dropped to 8:1!
I wonder what the C means on the Champion plugs. Another thread someone like Yellowrose or someone said it was a “better quality “ plug wtf?
I wonder what the C means on the Champion plugs. Another thread someone like Yellowrose or someone said it was a “better quality “ plug wtf?
mygasser
Well-Known Member
the 'c' is for crap 
We sold RN 12Y's to everyone back in the day for a run of the mill LA small block.
Locomotion
Well-Known Member
Lower # = lower heat range with Champion. R= resistor, C= copper.
340's started out with N9Y and used N12Y in 1973. Not sure about 1972 - may have been a transition year, like with forged to cast cranks.
Other 1970+ were usually-
426 Hemi= N10Y
/6=N14Y
318=N13Y
360=N12Y & N13Y
I had some N7Y and N63Y plugs long ago, which were considered cold race plugs. There was some footnote about N63Y and similar #plugs as far as heat range goes but I don't recall the details. See bottom of chart.
There are some plug crossover charts out there. Just gotta find the ones with the plugs & # code you're looking at.
340's started out with N9Y and used N12Y in 1973. Not sure about 1972 - may have been a transition year, like with forged to cast cranks.
Other 1970+ were usually-
426 Hemi= N10Y
/6=N14Y
318=N13Y
360=N12Y & N13Y
I had some N7Y and N63Y plugs long ago, which were considered cold race plugs. There was some footnote about N63Y and similar #plugs as far as heat range goes but I don't recall the details. See bottom of chart.
There are some plug crossover charts out there. Just gotta find the ones with the plugs & # code you're looking at.
A56
Street Survivor
Question "What Champion plugs are you running"?
NGK
Wouldn’t you need more/hotter spark in a lower compression engine?
1WildRT
Well-Known Member
R = resistor
N = 3/4" reach
7/9/11/14 = heat range
c = copper center electrode
Personally I haven't run Chumpions in over 40 years... they suck..
NGK or ND...
N = 3/4" reach
7/9/11/14 = heat range
c = copper center electrode
Personally I haven't run Chumpions in over 40 years... they suck..
NGK or ND...
1WildRT
Well-Known Member
Yes, Hot Plugs = lower compression, the hot plug reduces fouling... Cooler plug = higher compression, reduces detonation..
I agree with Locomotion. My 69 340 had N9Y's in it. I found a couple in an old tool box I kept spare parts in.
C= copper
What Champion Plug ru Using in you 340?
none, i only use ngk.
the 'c' is for crap
Am I doing something wrong??
Question "What Champion plugs are you running"?
NGK
I've run Champions in my mopars for 40 years, zero issues. My 360 in my Ram had 326,*** miles, ran fine with Champions on 100k mile changes. Now that I think of it, I haven't changed spark plug in our '80 Dodge 5.9 in 5 years. Nor in my Duster in 5 years. Nor my '89 van 360 in 5 years. All run perfect. Please help me understand..... Did I miss the memo ??
Me too. I have ran Champions in every Mopar I have owned since 69. Never an issue or misfire.Am I doing something wrong??
A56
Street Survivor
My comment was a reflection of some opinions that have nothing to do with the question. Happens quite a bit.Am I doing something wrong??
yeah, oil and spark plugs become fan favorite discussions, lolMy comment was a reflection of some opinions that have nothing to do with the question. Happens quite a bit.
A56
Street Survivor
Lmao, from my original '69 operators manual
68-72 340 per Champion dealer catalog is N9Y
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