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High-Performance Spark Plug Leads
Spark Plug Wire Leads
Manufactured for your specific application, MagForce
include a Kevlar
magnetic suppression core, with superior RFI
elimination to protect the most sensitive modern electronics from stray
noise and static. Durable stainless steel wound conductors create the
hottest spark for maximum horsepower and engine performance. Spark
plug and distributor terminals are also stainless steel for corrosion
resistance and maximum conductivity. Premium silicone jacketing and
OEM-style boots provide the ultimate in high-temperature protection,
with sealed barriers against heat, dirt and moisture.
Spark Plug Speak
Reading a Spark Plug
Spark plugs are the "window" into your engine (an eyewitness to what's hap-
pening in the combustion chamber), and can be a valuable diagnostic tool.
Like a patient's thermometer, the spark plug displays symptoms and condi-
tions of the engine's performance. The experienced tuner can analyze these
symptoms to track down the root cause of many problems, or to determine
air/fuel ratios. Being able to "read" a spark plug can be a valuable tuning aid.
By examining the insulator firing nose color, you can determine a great deal
about the engine's overall operating condition.
In general, a light tan/gray color tells you that the spark plug is working at
optimum temperature and that the engine is in good condition. Dark coloring,
such as heavy black wet or dry deposits can indicate an overly-rich condi-
tion, too cold a heat range spark plug, a possible vacuum leak, low compres-
sion, overly retarded timing or too large a plug gap. If the deposits are wet, it
can be an indication of a breached head gasket, poor oil control from ring or
valvetrain problems or an extremely rich condition-depending on the nature
of the liquid present at the firing tip. Signs of fouling or excessive heat must be
traced quickly to prevent further deterioration and possible engine damage.
Gap and Heat Range
Proper combustion depends on several factors, most importantly, the plug's abil-
ity to ignite the fuel/air mixture completely. The two attributes of a plug which have
the largest impact upon this process are the gap and the heat range.
the distance between the center electrode and the ground electrode
(the bent one). The spark travels across this distance to ignite the fuel/air
mixture. The precise distance is determined by the engine manufacturer and
is dependent upon the size of the cylinder and other factors. An improper
setting will result in misfires and a general decrease in combustion efficiency.
The correct gap setting can be found in the engine manual.
A spark plug's voltage requirement is directly proportionate to the gap size.
The larger the gap, the more voltage is needed. Experienced tuners know
that opening gaps up to present a larger spark to the air/fuel mixture en-
hances burn efficiency. That's why most racers add high power ignition sys-
tems. The added power allows them to open the gap yet still provide a strong
spark. With this in mind, many think the larger the gap the better, and some
aftermarket ignition systems boast that their systems can tolerate extreme
gaps. Be wary of such claims. In most cases, the largest gap you can run
may still be smaller than you think.
the theoretical "temperature" of the plug, determined by its ability
to dissipate heat away from its tip. This is also a precise measurement, as plugs
that are too "hot" are prone to pre-ignition, and plugs that are too "cold" fail to burn
the fuel/air mixture completely in the combustion cycle, which can leave deposits
and cause plug fouling over time. Consult the most recent engine manufacturer's
plug heat range guidelines, and read the application note. Let's make this really
simple: when you need your engine to run a little cooler, run a colder plug. When
you need your engine to run a little hotter, run a hotter spark plug. However,
going to a hotter spark plug can sometimes mask a serious symptom of another
problem that can lead to engine damage. Be very careful with heat ranges. Seek
professional guidance if you are unsure.
Champion spark plugs are available with stainless steel shells, which are im-
pervious to rust. NGK marine plugs are double-dipped with a zinc chromate
coating for corrosion resistance, and use cold-rolled threads to help prevent
spark plugs from seizing, even in aluminum heads or saltwater environments.
Wire-Wound Resistor Plugs
Champion and NGK recommend resistor plugs to eliminate RFI related false
readings on your depth/fishfinders or GPS and other navigation instruments.
Wire-wound (or inductive resistor) plugs also reduce static in audio and com-
munication systems, with no loss of ignition performance. Champion plugs of
this type have a "Q" (for Q-Type Suppressor) in their plug type name. NGK
plugs have an "R" (for Resistor).
OMC/OMC Cobra Selection Chart
OEM# SIERR #
, 80, 100, 110, 120(1965-74)
, 140 (1974-81), 140 Jet (1973) 503748 18-8800-1
3.8L, 4.3L7, 262 King Cobra (1989)
5.0L, 5.7L, 185, 200, 225, 225 (1976)
, 230, 230 IB
LH/RH (1976), 260(1979-81)
, 260 IB RH (1976),
260 LH (1976), 305 IB RH (1977-82)
, 305 IB LH
, 305 IB LH (1977-82)
, 305 IB RH
, 305 IB RH (1977-82)
, 350 IB RH
, 350 King Cobra (1989), 454 IB (1979-82)
370 King Cobra (1988), 460 King Cobra (1988-89) 503752 18-8803-2
1. 1974: Model FF and R only. 2. 1974: Model R1 only. 3. Model M only. 4. Models w/o closed cooling.
5. V-Drive model w/closed cooling. 6. Direct Drive Model w/closed cooling.
Volvo Penta Selection Chart
OEM SIERR #
AQ190A, AQ200B-F, AQ211A, AQ225B,D; AQ231A,B;
AQ240A, AQ255A-F, AQ260A,B; AQ271A-D, AQ290A,
AQ311A,B; BB225A-C, BB231A, BB260A-C, BB261A 8757166-7 18-8802-1
8 AQ190A, AQ200B-F, AQ211A, AQ225B,D;
AQ231A,B; AQ240A, AQ255A-F, AQ260A,B;
AQ271A-D, AQ290A, AQ311A,B; BB225A-C, BB231A,
MerCruiser Selection Chart
OEM# SIERR #
120 (153 CID), 140 (181 CID), 2.5L, 3.0L 84-816761Q5 18-8800-1
224 CID, 3.7L, 3.7XL
3.0LX Delco EST
185, 229 CID
262 CID, 4.3L,4.3XL, 4.3L EFI (TBI)
198 GM, 225 Ford, 225 GM, 228 GM, 233
Ford, 250 GM, 255 Ford, 260 GM, 280 GM,
330, 370, 400, 440, 460, 888 Ford, 898 GM 84-816761Q16 18-8803-2
260 TR, 305 CID LH & RH, 320 EFI, 330 TR,
350 CID LH& RH, 350 MAG, 420, 454 CID,
454 MAG, 5.0L, 5.7L, 7.4L, 7.4L IB
350 MAG Ski, 5.0L Alpha & Bravo (Gen+) 84-816608Q78 18-8821-1
350 MAG MPI MIE (Gen+) 350 MAG EFI
Ski, Black Scorpion Ski (Gen+), 350 CID,
454 EFI MAG MPI & Horizon MIE, 502
MAG, 502 EFI & MAG MPI
5.0L MIE MPI
454 Hi Perf.
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