84 Fifth OE spark plugs

[rcmaniac791]

So the sticker under the hood says that the OE spark plugs are Champion RN12YC with a .35 gap. I went online to look for pricing info to see where to get them cheapest, and every auto parts place is telling me that the OE plug for my car is the RN14YC. What's the difference? Should I just stick with the what my car tells me it came with?

 

[Jack Meoff]

R - Resistor Plug
N - 14mm Thread, 3/4" Reach, 13/16" Hex
14 - Heat Range
Y - Standard Projected Core Nose
C - Copper Plus Design

12 and 14 are different heat ranges. I'd have to look up the differences. Don't know them off hand. My factory service manual says RN12YC's.

That being said I've heard mixed reviews on Champion over the past few years. It's rumored they're Chinese now. Some folks still swear by them and others bailed on them.

I run NGK ZRF 5N's in my Fifth. They sit a squeak lower and apparently fire the mixture better. That's what I read in an article from one of the engine designers at Chrysler a while back. So I tried them. I've had the same set in for roughly 4 years and they run great.

Seems to be a personal choice thing but I'm happy with the NGK's. The "12"YC's are still out there though if that's what you want.

Also keep in mind that the "experts" telling you what is OE for your car are primarily kids on a computer as opposed to real mechanics or knowledgeable car guys.

 

[brotherGood]

Run into that problem constantly with my magnum heads. Idk how many times I've walked out, grabbed the plug and walked back in. Last time, I told him the number and he said he didn't have it, but he had what the computer caled for. So, I went to another guy who pulled it right off the shelf.

I still run champions, ive heard mixed reviews on them, and NGK. I figure keep what's factory in it (says the guy with a no longer factory car)

 

[rcmaniac791]

Ok, I'll stick with the OE plugs and see how that does.

 

[89.Fifth]

Also try looking up plugs for 1996 Grand Cherokee with the 5.2

The Magnum motors used a projected nose plug that helps cold firing

Champion RN12PYC
Bosch FR8LYC

 

[NoCar340]

Keep in mind, a plug's heat range has absolutely no effect on spark energy. An RN12YC will make exactly the same spark as an RN14YC at the same gap. Heat range is a measure of how quickly heat is transferred from the center electrode and the ceramic insulator's protrusion around it to the cylinder head.

If you've got a stock engine you drive like an old lady and things like emissions and a 20-second-quicker-overall warmup time are important to you, use the RN14YC. If you've got a beater engine that fouls plugs, these will also take longer to foul... but fix your junk, man!
If you like a little kick in the pants from your car, and especially if you've added a four-barrel, free-flowing exhaust, etc. in order to get one, use the RN12YC and throw the factory timing specs out the window. Starting with static (idle) timing of 6-8°BTDC is a very safe, conservative start. Unless it results in preignition or detonation, more timing means more power and better economy. Search "big fat friend" on this site for a proven way to get the most out of your car without killing it, requiring nothing more technical than a chubby buddy and a basic timing light.

The number of guys I see that are terrified to time their engines at any other number than what the manual or underhood decal says is very frustrating. It's free HP and MPG, and makes for a much-more-enjoyable car, even with a stock Slant Six. This ain't my first rant about this and it won't be my last.

The Magnum motors used a projected nose plug that helps cold firing

Champion RN12PYC

Actually, it's an RC12PYC. The Y is what indicates the projected nose; Mopars have used that design for several decades. The P indicates it as a platinum. In other words, an RC12YC is the exact-same plug with a copper electrode. An RN12YC is the same plug in copper, with a larger hex. The only difference between the RC plugs and the RNs is the hex size:
RC = 5/8"
RN = 13/16"
Header owners take note... that smaller hex can make life a lot easier around your bundle of snakes.

Also worth noting: For all their expense and the advertising money spent promoting them, platinum and iridium plugs are not high performance parts and are not worth the money from a performance standpoint. Copper plugs have lower resistance and transfer more spark energy to the electrode than platinum or iridium. This is basic physics, carved in stone on the Periodic Table of Elements. For the same reason, copper plugs are harder to foul. Simply put, if you fit the RN14YC guidelines above other than fouling, you'll probably love platinums. If you picture yourself more in the RN12YC camp, buy the less-expensive, better-sparking standard copper plugs, but expect to change them more often... like, y'know, every 25,000 miles or so.

 

[Aspen500]

Good info NoCar! I've found that older, meaning non computer controlled, non fuel injected (etc) engines run better on plain copper plugs for whatever reason. The iridium and platinum work better in engines designed for them. They also last like 100,000 miles but in our cars, that isn't really a factor to worry about.

As for Champion plugs,,,,,,,I've fixed a lot of vehicles with random misfires or slight misfire on light acceleration, hard starting and various other ignition related driveability problems by replacing either fairly new or perfectly good looking Champions with (for example) Motorcraft or AC over the years at work and on my own stuff. Just my experience though and some guys have good luck with them.

I'll admit to having NGK in my Aspen and they work just fine. Your results may vary. Honestly, the Motorcraft and AC plugs are some of the best plugs out there.

 

[NoCar340]

AC Delco has not made a spark plug in over 20 years. Their plugs are made for them by NGK and... wait for it... Champion. It's true.

I love to drop that bomb on GM guys and just walk away, but the truth of it is that much like Mopar oil filters being made by Allied Signal but being better than Fram junk, Champion and NGK make the AC Delco plugs to AC's specifications. However, if you're curious the next time you have an AC plug in your hand, look for a row of slashes around the base below the hex: ////////////////. It goes all the way around the plug. That's a Champion Spark Plug "maker's mark" just like a finding a cast-in snowflake on an aluminum part means it was cast by Winters Foundries. If you see it on an AC plug it's defintely made by Champion.

Very important: Never use a cross-reference to determine what spark plug to put in your engine. Always use the catalog application guide. Spark-plug companies are full of smart people; it's not that they've never heard of (or forgot about) your dual-fuel 1957 Farmall D450. They just don't make a plug they feel is suitable for it, regardless of whether another manufacturer's plug crosses to it. If it's not in the application guide, choose a different brand. Period.

As far as the EFI/carbureted thing, I've definitely had better luck with Champions in Chryslers (non-Mitsu) and ACs in GMs on both the carbureted and EFI end. Then again, the newest MPFI vehicle I've owned for any length of time is my '92 Dakota 3.9L. I will say this, though, I can't remember if my 340 Challenger ran worse with ACs than my 455 Pontiac ran with Champions, but in both cases the plugs were removed the same day and replaced with what the factory recommended. It was literally that bad. I know Mopar guys from both eras that love Autolites; my experimentation with those many (over 20) years back on carbed engines kept me well dug into the "Champions in a Mopar" trenches. However, I've sold a ton of NGK and Denso platinums for GM applications simply due to cost. ACs are often twice as expensive as either. It's hard to sell $50 worth of spark plugs to a guy with a 17-year-old K1500. I've never had a problem or a complaint, so I would tend to agree that in the multi-port era, the differences are not as large.

On the flip side of that, if you own a coil-on-plug Ford, I would highly advise you to use Motorcraft plugs only. For whatever reason, Ford used very-specific coil drivers in many of their PCMs. Changing to a different brand of plug, even Autolite (who makes Motorcraft--again, that doesn't mean they're the same), can and has burned up the coil drivers in the PCM. The 2004-06 Ford Escape/'05-'06 Mercury Mariner and Mazda Tribute with the 3.0 V6 were so bad, there were multiple Ford TSBs, some of which were withdrawn, dealing with those vehicles' appetite for PCMs. One of said TSBs regarded using only Motorcraft plugs in the engine. Sure enough, back in 2010 I sold a set of Autolites to a customer working on an '05 Escape, and a week later it was back in his shop with a dead miss on #1. It was a burned coil driver, and it turned into one of my biggest nightmares ever as a parts guy. To this day, those PCMs are "R&R only"--meaning you've got to send yours in for remanufacturing; good cores and junkyard PCMs don't exist.

Based on that experience alone, whatever the factory used is what I'm going to use. Things are only getting tweakier under the hood with each new model year.

 

[rcmaniac791]

Certainly some good info here. I bought the RN12YC's and threw those in today, also fixed a huge vacuum leak because all 4 carb mounting bolts were loose. Now it purrs like a kitten. I'm going to take it out on the highway tomorrow and cruise some.

 

[Jack Meoff]

Great news.
Enjoy that thing.

 

[metallicaman0258]

AC Delco has not made a spark plug in over 20 years. Their plugs are made for them by NGK and... wait for it... Champion. It's true.

I love to drop that bomb on GM guys and just walk away, but the truth of it is that much like Mopar oil filters being made by Allied Signal but being better than Fram junk, Champion and NGK make the AC Delco plugs to AC's specifications. However, if you're curious the next time you have an AC plug in your hand, look for a row of slashes around the base below the hex: ////////////////. It goes all the way around the plug. That's a Champion Spark Plug "maker's mark" just like a finding a cast-in snowflake on an aluminum part means it was cast by Winters Foundries. If you see it on an AC plug it's defintely made by Champion.

Very important: Never use a cross-reference to determine what spark plug to put in your engine. Always use the catalog application guide. Spark-plug companies are full of smart people; it's not that they've never heard of (or forgot about) your dual-fuel 1957 Farmall D450. They just don't make a plug they feel is suitable for it, regardless of whether another manufacturer's plug crosses to it. If it's not in the application guide, choose a different brand. Period.

As far as the EFI/carbureted thing, I've definitely had better luck with Champions in Chryslers (non-Mitsu) and ACs in GMs on both the carbureted and EFI end. Then again, the newest MPFI vehicle I've owned for any length of time is my '92 Dakota 3.9L. I will say this, though, I can't remember if my 340 Challenger ran worse with ACs than my 455 Pontiac ran with Champions, but in both cases the plugs were removed the same day and replaced with what the factory recommended. It was literally that bad. I know Mopar guys from both eras that love Autolites; my experimentation with those many (over 20) years back on carbed engines kept me well dug into the "Champions in a Mopar" trenches. However, I've sold a ton of NGK and Denso platinums for GM applications simply due to cost. ACs are often twice as expensive as either. It's hard to sell $50 worth of spark plugs to a guy with a 17-year-old K1500. I've never had a problem or a complaint, so I would tend to agree that in the multi-port era, the differences are not as large.

On the flip side of that, if you own a coil-on-plug Ford, I would highly advise you to use Motorcraft plugs only. For whatever reason, Ford used very-specific coil drivers in many of their PCMs. Changing to a different brand of plug, even Autolite (who makes Motorcraft--again, that doesn't mean they're the same), can and has burned up the coil drivers in the PCM. The 2004-06 Ford Escape/'05-'06 Mercury Mariner and Mazda Tribute with the 3.0 V6 were so bad, there were multiple Ford TSBs, some of which were withdrawn, dealing with those vehicles' appetite for PCMs. One of said TSBs regarded using only Motorcraft plugs in the engine. Sure enough, back in 2010 I sold a set of Autolites to a customer working on an '05 Escape, and a week later it was back in his shop with a dead miss on #1. It was a burned coil driver, and it turned into one of my biggest nightmares ever as a parts guy. To this day, those PCMs are "R&R only"--meaning you've got to send yours in for remanufacturing; good cores and junkyard PCMs don't exist.

Based on that experience alone, whatever the factory used is what I'm going to use. Things are only getting tweakier under the hood with each new model year.

Gospel truth. I worked in auto parts for 5 years. and this is so true it should sticky.

I cant tell you the number of Jeep (AMC and Chrysler) and Chrysler guys that came to me with "it just ain't runnin' right and the plugs are only 2 weeks old". i would talk them into a set of standard Champion copper plugs (I wouldn't use a Champion in a lawn mower!) only for them to come back in a few days and thank me. I don't know the science behind it but Mopars (and AMCs) love a Champion plug