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 Spark Plugs for Magnum engines - DiRT

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[DiRT] Re: Spark plugs again ( Standard Answer - add your comments)

Date: Sat, 26 Aug 2000 08:15:09 -0400

From: "DiRT Mail List"

Subject: 'What sparkplugs will fit a Magnum engine in a 1994+ Ram or Dakota pickup? '

Here are some sparkplugs that will fit:

RAM 5.2/5.9 V8 PLUGS


Champion RC12YC is the 1993-2000 factory installed plug.

Champion RC12LYC is a longer 'projected nose' plug used in the Viper V10.

Champion RC11YC is one heat range cooler and is part number 3344.

Champion RC9YC is an even colder heat range available locally,

or Champions can be got by mail order from

Champion Truck Plugs P/N 4071

another better Champion sparkplug site at:

Autolite Double Platinum Pro APP3924

(APP3923 is a colder heat range platinum plug)

Autolite 3924 or cooler 3923

Many Dakota owners who drag race their trucks recommend

this relatively inexpensive ($0.99 at Walmart) plug, and some claim to have

chassis dyno results showing 4-5 hp improvements. See dyno graph at this


Autolite 5224 conventional metal tip

Autolite 5223 is a colder heat range plug

The 522? series is similar to the 392?, but has a longer 'projected nose' than

the 392? design that puts the spark farther down in the chamber, which has an


similar to slightly advancing the ignition timing 2-3 degrees. Note this

timing effect might increase pinging if timing/carbon deposits are at 'the


Bosch Platinums (old style, not +4's) FR8DPX, P/N 4102 (gap .044)

Bosch Platinum FR7DPX p/n 4202 is a similar but colder heat range plug.

{these are 'fine wire' tip sparkplugs that seem to give exceptionally quick

cold starts and good mpg on Interstate driving. Increased gaps up to 0.050

seem to work ok. Standard gap out of the package is 0.043}

Mopar Performance recommends and sells Bosch conventional

metal tip sparkplugs in their 2000 year catalog for mopar engines, and

gives a table of interchanges on page 125.

Bosch Platinum Super+4, P/N 4418

{but not recommended by Bosch for truck, towing, or high

performance/racing applications. Seems to give quick starts, smooth idle - but

has been accused by Dakota owners of increased pinging. Consumer Reports

found no mpg difference when compared to factory NGK sparkplugs on a Honda.

1995 Ram 5.9V8 owner on four 300+ mile test runs over same stretches of

Interstate 95 from NC to FL found 2% worse mpg with Bosch Super+4 plugs

compared to Bosch FR7DPX gapped at 0.050 }

NGK FR5-1, P/N 7252

NGK platinum tipped PFR6J-11, P/N 2743 (colder plug).


Kenne Bell recommends after extensive research and testing

the "V" design NGKZFR5F11 for non-supercharged,

and ZFR6F11 (one heat range cooler) for blown 5.2/5.9 Dodges.

The ZFR5F11 is NGK's Viper V-10 plug -- with a nose that

projects farther into the combustion chamber.

AC Delco Rapid Fires, P/N 5

{ some Ram owners report the Rapid Fire plugs give a

smoother than stock idle, and the p/n 5 is supposed to be a


relatively cool heat range. GM did hire an independent firm to test these

sparkplugs in fleet use, and some gains were found.}

In the Splitfire Catalog it specifies that a 5.9 Magnum V-8

uses different plugs for different years:

A '95 360 uses plug "SF392D" with a .035 gap

A '99 360 uses plug "SF522D" with a .040 gap

Torque Master, P/N VFN8BR ($12.50 per plug)


Switching to larger hex (old style) sparkplugs from the 'peanut' plugs used on

the 1992+ Magnum engines:

If the heat shields around Magnum engine sparkplug holes are

removed by gently squeezing them with channel lock pliers, Champion 'N'

series sparkplugs with the 5/8 hex nut flats can be fitted to

3.9V6/5.2V8/5.9V8 Magnum engines, but a special sparkplug socket must be

ground down on a grinder to a small enough diameter to fully tighten the

sparkplug - otherwise an unmodified sparkplug socket will hit the hole

designed to retain the now removed heat shield. A cheap stamped metal 'lawn

mower' sparkplugs socket works well for this. Some prefer to use N series

Champion sparkplugs because a wide variety of heat ranges are available.


The Dodge Stealth 3.0L V6 DOHC Turbo

"trick" to find a colder heat range sparkplug for your Ram

pickup when dealing with non-knowledgeable parts counter attendants.

If you want a colder heat range sparkplug, because you

aggressively drive your truck and keep the throttle more wide open than most,

you can find a colder range sparkplug by asking for one for a 1995 Dodge

Stealth 3.0L V6 Double Overhead Cam Turbocharged engine. Sparkplugs

recommended by any sparkplug manufacturer for this application are 1-2 heat

ranges cooler than the factory Ram sparkplugs, but these 'Stealth' plugs are

the same physical size.

Warning: colder heat range sparkplugs foul easily, quit

sparking, create more pollution, and give lower mpg when the engine is not

driven at wider throttle openings frequently to burn away carbon deposits.

This can also cause hard cold starting and a miss at idle. Prolonged

running of an engine with fouled sparkplugs can overheat and ruin a catalytic

converter that is getting unburned gasoline dumped into it.


Originally posted on Eric P's site, this information was reposed from archived data.
If I find Eric's web page, I will return the link to there.

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This page was edited on: May 3, 2004