Collected wisdom from the DiRT list and sparkplug manuals
Q: Which sparkplugs will fit a Magnum engine in a 1994+ Ram or Dakota pickup?
The Ram V-6 and V-8 engines use a plug with:
|1993-2000 RAM 3.9 V6, 5.2/5.9 V8 PLUGS|
|Champion||Champion Truck||Autolite||Autolite Platinum|
|Champion RC12LYC is a longer 'projected nose' plug used in the Viper V10.|
Champions are available from www.edelbrock.com, www.federalmogul.com,
Subject: DiRT: Engine Ping
Date: Fri, 18 Jun 1999 11:21:03 EDT
To all you Rammers out there with pinging gas engines, listen up! I had a pinging beast which was driving me crazy. First tried switching to 89 octane fuel, no change. Next was the TSB for rerouting plug wires, no change.
Figured I would try a spark plug change, BINGO. Switched to Champion Truck Plugs and NO MORE PING. The plugs are much different dimensionally (shorter) than the factory Champions. Don't know the exact reason why the pinging has stopped but it is wonderful and the truck runs as well as, if not better, than before. Solved the one problem my otherwise perfect Ram was experiencing. These plugs should be factory standard equipment!
Rich Busch - Pittsburgh, PA.
98 QC SB 4X4 5.2L AUTO
Subject: DiRT: Re: Spark Plugs ( V6/plug numbers/slightly colder)
Date: Tue, 4 May 1999 09:51:45 -0400
From: firstname.lastname@example.org (Henry LaViers)
> I have a RAM 1500 V-6, and I was following the discussion on the Truck Plug threads
> and was wondering does anyone have a V-6 and have any smashes or trashes regarding
> other non-Mopar plugs
Your V6 should be alot like a 318 V8 - as they share the same bore and stroke - except with your lower horsepower you probably have to keep the throttle more open than a V8 - even as a daily driver.
Even though Dodge puts the same sparkplug in your V6, I think a V6 should get a slightly colder plug because of this. The more open the throttle, the colder heat range the best sparkplug will be.
I wouldn't replace with the stock Champion RC12YC. I would go to at least a RC11YC or maybe a RC10YC - which are colder plugs less prone to preignition at wide open throttle. The Champion Truck Plug recommended for the Magnum engines ( Champion stock number 4071 - can someone email me the letters/numbers on the actual "Truck Plug") seems to be a colder heat range plug too.
Champion makes a "Double Platinum" type plug that is original equipment on several cars - this might be a good plug style to switch to. They claim it is their top of the line plug and warrantee it to last 5 years/ unlimited mileage.
The regular style Bosch sparkplug with a platinum centertip for the Magnums is stock number 4102, Bosch Plug No. FR8DPX. This seems to be a slightly colder plug than the stock Champion RC12YC but it never seems to foul. Starts great. I use it in my 360 V8.
NGK recommends for the Dodge Magnum 3.9/5.2/5.9 their "V power" sparkplug FR4, stock number 5155 or their FR5-1, stock number 7252. (NGK does heat range numbers opposite that of Champion, so the FR4 is hotter than the colder FR5-1. I would go with the FR5.)
See my post on how to read a Champion Sparkplug's numbers.
DiRT listers who know the Magnum recommended Autolite, AC Delco Rapidfire, and Splitfire plug numbers/stock numbers should post them.
Subject: DiRT: TruckPlugs
Date: Mon, 24 May 1999 01:02:07 -0400
From: "Martin C. Olson" email@example.com
I have a 96 Dodge Ram 1500 with the 3.9L V-6 and I just installed a set of TruckPlugs (#4071) and I am very impressed with the performance with the plugs.
I did not expect the plugs to make a big difference one way or the other. Since installing, the idle is noticably smooter and when I get on it a little bit it seems to move out strongly without a lot of complaining.
The old plugs looked good for normal wear and tear. The plugs had 25,000 on them and the gap ranged from .37 to .40.
I gapped the new plugs at .35 per specs. They seem to be working fine. Thanks for all the recommendations. I guess the only way to compare them would be to try a set of new factory plugs, but this is my daily driver and I don't have time for that. If you are interested, I would give them a try.
Subject: Re: DiRT: Spark Plug Gaps
Date: Mon, 17 May 1999 22:26:04 -0400
From: "Tim Brennan"
From the 1996 Service Manual:
- Engine:3.9L V6
- Spark Plug:RC12YC
- Gap .035" (0.9 MM)
Subject: RE: DiRT: need a better spark
Here are some that I have archived, in no particular order:
- Bosch Platinum +4, P/N 4418 (but not intended for truck applications)
- Bosch Platinums (old style, not +4's) FR8DPX, P/N 4102
- AC Delco Rapid Fires, P/N 5
- Torque Master, P/N VFN8BR ($12.50 per plug) http://www.torquemaster.com
- Champion Truck Plugs P/N 4071
- NGK FR5-1, P/N 7252
- Autolite Double Platinum
Subject: DiRT: Addition to Bob B's sparkplug table (V10 plugs for V8s ?)
Date: Thu, 24 Jun 1999 15:47:13 -0400
From: firstname.lastname@example.org (Henry LaViers)
I was talking to a parts guy today and was shown three V10 sparkplugs:
1. The '95 stock factory sparkplug for the Dodge V10 is a Champion Copper Plus RC9MC4 and the 1995-1999 is a QC9MC4 where the Q instead of the R means the resistor is a "wire wound" instead of the SAC semiconductor that Champion primarily uses. I don't know why they went to the Q from the R.
2. A TruckPlug for the V10, which I think was stk number 4334(?).
This plug looks just like the stk number 4071 TruckPlug specified for the 5.2/5.9 Magnum V8's but the Champion catalog's heat range table shows these two plugs by themselves in a seperate column with the 4334 on top of the 4017 - which means it is a colder plug than the 4071. The gap seems to be 0.045
3. The Autolite No. 5224 for the Dodge V10. This is not the "Double Platinum' plug, but the standard electrode type, but I am told the Double Platinum looks the same. What is interesting about this Autolite sparkplug is that is has a longer "projected nose" than the stock Champion or the TruckPlug. As best I can measure, the 5224 sticks out 8 mm and the Champion 4071 sticks out 6mm. A longer projected nose is supposed to start the spark closer to the piston top and may produce more horsepower, similar to advancing the timing a few degrees. It also seems to have an even larger gap - 0.050
I wonder if the V10 sparkplugs can be used in the V8's ?
It would seem to me that if you made sure the ground electrode is not pointing down then there should be enough clearance not to hit the top of the piston. The V10 does have a lower compression ratio (8.6 versus 8.9) so that may mean there is more piston to sparkplug clearance in a V10.
My theory is that the "heavy truck" 2500 series where the V10s are available don't have to pass as strict a 50,000 mile EPA emissions durability test - so Chrysler put the right sparkplug for performance in them - instead of the "emissions" RC12YC (very hot heat range for nonfouling) that seems to cause pinging in the V8s when you put your foot down.
Subject: DiRT: Platinum+4s
Date: Mon, 17 May 1999 20:15:48 -0400
From: "Dick Campagna" email@example.com
The June '99 issue of Consumer Reports has an article (p. 9) on the Bosch Platinum+4 spark plugs. They tested 'em on a high-mileage Honda and made a series of timed acceleration runs and their standard fuel-economy tests, which combine city and highway driving. They ran the tests with a new set of standard NGK spark plugs recommended in the Accord's owner's manual, then again with the Platinum+4 plugs. They found ". . . no meaningful difference between the regular plugs and the Platinum+4s
." They do prefer platinum-tipped single-prong spark plugs ". . . because they last longer - typically 100,000 miles between changes instead of about 30,000."
Dick (& Geri) Campagna, Mt Laurel NJ
'95 Ram 1500/CC/SB/5.9-V8/auto/2WD/3.5/Flowmaster/RhinoLiner/5W hitch
Subject: DiRT: What the letters/numbers on Champion sparkplugs mean
Date: Tue, 4 May 1999 10:02:50 -0400
From: firstname.lastname@example.org (Henry LaViers)
The stock plug for the Dodge Magnum 318/360 V8s and the 3.9L V6 is the Champion RC12YC so we will use it as an example.
I wrote an email to Champion about a week ago asking if they had a booklet explaining what the numbers and letters mean. Yesterday in the snail mail I got two booklets:
"High Performance Heat Range Chart and Tuning Guide" reorder No. 98770 and
"The Spark Plug Handbook" Reorder No. 99084
The SP Handbook (now posted here) was on the web at the (now defunct) Cooper Auto site but the Heat Range Chart is not. Both are great little 3 by 8 inch booklets with full color photographs.
If the first letter is "R" it stands for resister. A plug without a resistor would just be called a C12YC. There is some evidence that resistor plugs give slightly better gas mileage, according to both the Champion and NGK websites. The resistor delays the spark initiation but makes it hotter once it does fire.
The "C" is the 'shell' type and sets the threads and hex size. A "C" shell has a 14 mm thread, a 0.750 inch reach (reach is the length of thread), and a 5/8 inch hex bolt size for your sparkplug wrench. The "N" shell is similar to the "C" shell but has a 13/16 hex. Other shells are G, A, J, V, L, and S. The other shells won't fit the Magnum engines - except - the S shell has a .708 inch reach but is otherwise like the C shell. Put one of these 'S' in your Magnum and it would reduce the compression ratio a tiny bit. This might be useful for supercharged engines.
The "12" is the heat range. 12 is about as 'hot' as they go. Champion says that the ditty to remember is:
"Put a hot plug in a cold engine and a cold plug in hot engine."
I think the reason Dodge chose a 12 heat range plug is to pass emissions tests - which simulate stop and go city driving. This is cold engine type driving and the hot plug is there to keep the plug from fouling. The booklets mention that Champion makes colder plugs down at least to a RC9YC .
n Champion's racing sparkplugs they go to a two number heat range system that goes from 69 (hot) to 51 (cold). All racing plugs are very cold and not recommended for street use. In the booklet they have a chart that shows that a RC9YC is about the same heat range as a racing C67YC. This chart also shows that a 'N' shell RN5C is about the same heat range as a 'C' shell RC9YC. Yes, it can be confusing.
The "YC" means "Projected Nose." Quoting from Champion......
"This gap style projects the spark an additional .060 inch into the combustion chamber for a total projection of 0.210 inch, and providing there is sufficient clearance to valves and pistons, provides the ultimate in performance. Initiating the flame front closer to the center of the combustion chamber has a similar effect to advancing the timing. Therefore, maximum timing may be reduced which helps reduce the chance of detonation and provides superior part throttle response. A second valuable feature of this style is a broader heat range. The core nose is longer, providing a 'hotter' plug at low speed which helps prevent fouling. As engine speed increases, the incoming air/fuel mixture flows across the tip of the core nose, providing charge cooling which effectively reduces heat range at higher engine speeds for increased preignition and detonation protection."
Other gap styles from Champion are:
The V10 takes a Champion QC9MC4 which I haven't been able to completely understand yet - the Q or the MC4 - except that one of Champion's experts emailed that:
'Yes, the 12 is a hotter plug than the 9. That rule applies as long as you stay within the "family",which is the projected tip style in this case.' Ron.Dohr@cooperauto.com
Reading Spark Plugs
Close inspection of the spark plugs can reveal much about how the engine is running.
This page was edited on: May 3, 2004