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4.6L Ignition Systems
The 4.6-liter engine rolled out the door of the factory with a computer controlled ignition system.
There were 2 coil packs mounted on the front of the engine, each with 4 plug wires connected to
them. The coils are fired by the computer in pairs, which is why it’s known as a waste-spark system.
Cylinders 1 and 6, for example, would fire at the same time, and while one of the cylinders would
require ignition, the other would be on the exhaust stroke, and therefore not require any spark
energy. There were, therefore, 4 channels from the computer, each firing 2 cylinders. In 1999, the
4.6 Mustang went to coil-on-plug ignition, where each cylinder had its own coil, directly on top of the
spark plug. The computer triggered the coil, so now we had 8 channels, each firing one cylinder.
Both systems have their idiosyncrasies, which we will discuss.
Spark Plugs
The first point of discussion on the 4.6-liter engine is the type of plugs that should be used. The
stock engine comes with platinum-tip spark plugs and a recommended plug gap of .055 inch. The
platinum spark plug is largely used by the OEM manufacturers to achieve the 50,000-mile
emissions warranty required of them by the federal government. Platinum plugs do provide good
service in stock and mildly modified cars and trucks. I am sometimes asked why the spark plugs on
new Ford 4.6 cars have different part numbers on the plugs from the left and right cylinder banks.
The reason is that there is a small button of material on the ground electrode on one bank of plugs,
and on the center electrode on the other bank. This extra material is to compensate for erosion of
the plug as it fires, and one bank fires from the center electrode to the ground strap, while the other
bank fires in the reverse direction, from the ground strap to the center electrode. These plugs are
replaced with service replacements which all have the extra material on the center electrode,
because once the plugs are changed, Ford does not have to meet the 50,000-mile emission
requirement any more.
Motorcraft NGK and Nippondenso 4.6 Liter Spark Plugs Compared
The standard Motorcraft platinum-tip
spark plug is on the left. The NGK TR6
copper-core plug in the center is an
excellent performance replacement.
The Nippondenso iridium plug on the
right can provide better ignition
performance in marginal situations.
The preferred plug for most performance applications is the NGK TR6 copper-core spark plug. The
copper core conducts current well, and I recommend the gap be set at .035 inch for
naturally-aspirated (NA) engines, and .030 inch for forced induction. The small gain in power to be
obtained with a larger gap is more than offset by the very real possibility of misfires with high
cylinder pressures. This plug is one heat range colder than a stock plug; the TR5 would be the
same heat range as the original. Spark plugs on supercharged and nitrous engines should be
replaced at regular intervals. There is no way a spark plug is going to have a long service life in this
harsh environment, and replacing plugs regularly is just part of the price of admission. On a street
car, plugs should be changed once a year, or every 12,000 miles, whichever occurs first. With a
dual purpose or track-only car, plugs need to be inspected every time the car is at the track, and
replaced as often as inspection dictates.

Some ignition systems will work with Champion race spark plugs, but not all of them. Electromotive
Tec2 and Tec3 systems will work with the Champions, but the production 99-up coil-on-plug coils
will not work with the Champion race plugs, even with an aftermarket ECM. The Champion race
plugs are not resistor-type plugs, so they cause interference with some systems.
The Champion is available in a multitude of configurations and heat ranges, but there are a few we
have used commonly. S59YC is the most common Champion plug we use in supercharged engines
to 1600 hp. There are S57YC and RS9YC plugs as well, which are colder and hotter respectively.
On NA engines, we sometimes need to use the S59C plug, which does not have a projected nose.
With a domed piston, there is not always room to accommodate a projected nose plug. This plug is
also available as a S57C, S55C, or S53C, all colder than stock. The Champion plugs have a more
brittle insulator material than the ceramic found on the NGK plug. If too much spark advance is
dialed up, the resulting detonation can break the ceramic right off the nose of the plug. The
subsequent bouncing around this material does in the combustion chamber makes a mess of all
kinds of things.
Champion Projected Nose Spark Plug Compared to a Non Projected Nose Plug
Champion race spark
plugs are available in
projected-nose design, like
the S59YC on the right, or
in a non-projected nose for
use with domed pistons,
like the S57C on the left.
The newest spark plug on the block is the Denso Iridium plug. This plug seems to have a higher
temperature tolerance, which helps in marginal situations. It also seems to require less current to
fire, which again helps in some areas. If you have an engine that misfires under high cylinder
pressure, this plug may get you by without switching to a better ignition system. The stock heat
range in the Denso Iridium plug is their IT16. The IT 20 is a colder plug that is suitable for
supercharged engines up to 10 pounds of boost. The plugs are available in three stages colder
yet, IT22, IT24, and IT27. The heat range should be one step colder for every 6-8 lbs of boost
added, or for every 50 horsepower shot of nitrous added. Similar to some issues I have seen with
the Champion race plugs, the coil-on-plug factory ignition seems intolerant of too cold a spark plug.
It seems the engine needs to see a certain degree of plug temperature or a power loss ensues.

On racing and high-performance engines, sometimes the spark plug appears to have a leak
between the insulator and the spark plug body. In fact, the seal between the two is leaking and
combustion gasses escaping past the seal cause the brownish color on the insulator. Plugs that
exhibit this leakage are toast, so replace them immediately.
Indexing the spark plug ground strap seems to provide some power. On the 4-valve engine, the
ground strap should face the exhaust valves, exposing the spark to the intake valve side of the
chamber. In the case of the 2-valve engine, the ground strap should face the wall of the combustion
chamber, aiming the spark, as it were, towards the far side of the combustion chamber.

It should be noted that all the aftermarket plugs we have discussed are .708-inch reach,
conical-seat plugs with a 5/8-inch hex. The production Motorcraft spark plug is only threaded on the
bottom .375 inch of the body. This poses no problems for the aftermarket plugs, as there is
adequate clearance in the cylinder head. The Ford Motorsport SVO cylinder head, in fact, is
machined to accept only a fully threaded plug like the aftermarket plugs we are talking about. I
caution you to not over torque the spark plugs into the cylinder head, use only 20 ft-lbs of torque to
install. A small amount of anti-seize compound may be used on the threads if required. If the plugs
need to be removed, let the engine cool first. The primary cause of damaged threads on the
aluminum cylinder heads is trying to remove the plugs when the head is still too hot. The aluminum
material expands when warm, and the plug is going to take more turning effort to loosen than when
the head has cooled. So, patience and care are the order of the day.
Ignition Wires
In the beginning, as more supercharger boost was applied to the 4.6, the spark blew out. Changing
to a copper-core plug gapped at .030 inch helped, but did not cure all cases. As more boost was
brought to the party, the problem intensified. At the time, the only improvement available was to fit
Nology spark plug wires. These plug wires contain a capacitor in the cable that stores the charge
and releases it with more effect. There was measurable improvement on supercharged systems
with this and we used them for a couple of years. The arrival of aftermarket spark boxes did away
with the need for the Nology wires.
Nology spark plug wire
Nology spark plug wires
use a capacitor built into
the wire to increase the
spark intensity. Note the
ground wire included with
the plug wire, which
attaches to the engine.
The original Ford plug wire is alright for medium performance applications, but like all plug wires,
deteriorates after time, and heat take its toll. Be careful when removing plug wires on the 4-valve
engine, not to damage the spark plug wire boot. It is easy to rip the wire end out of the boot, and is
always best to grip the boot itself firmly to remove it from the valve cover. A little Vaseline on the
outer edge of the boot can help removing them the next time. For best performance, plug wires
should be replaced after 2-3 years of service. The plug wires may still check out with an ohmmeter,
but the insulation will break down and crossfire may occur, so it is best just to replace them on time,
not mileage. This brings up a good point, actually. The firing order on the 4.6 and 5.4 is
1,3,7,2,6,5,4,8. Because cylinders 6 and 5 fire consecutively, these two plug wires need to be
routed away from each other. Placing any length of these two cylinders wires parallel to each other,
invites inductive cross fire, which could be quite destructive.

An improvement on the OEM wires is to replace them with high-performance wires from an
aftermarket supplier. MSD has an 8.5-mm high-performance wire set available for both SOHC and
DOHC modular engines. Their wire features a copper-alloy conductor, surrounded by glass braid
insulation and a silicone sleeve. ACCEL also produces wire sets for the 4.6. They offer an 8.8-mm
race wire with Kevlar core stranding surrounded by a copper-nickel alloy. A silicone insulator layer
is covered with a silicone jacket rated for 600 degrees. Both these wire sets will offer improved
performance and less voltage drop compared to the production carbon/graphite-core wire set.
There are a couple of companies pushing 10-mm wire sets out there for the 4.6, but they do not
package well due to the extra bulk of the wire. They will not fit in the wire looms, and do not fit below
the wire covers on the DOHC valve covers.
MSD 8.5 mm high-performance ignition 
MSD 8.5-mm
high-performance ignition
wires are a worthy upgrade
for the OEM wires. Wire sets
are available for both 2-valve
and 4-valve engines.
Ignition Coils
The factory ‘92-‘98 EDIS coil is perfectly acceptable for medium-duty performance engines. As long
as the coil is in good operating condition, it may be used. I have seen some of these coils develop
cracks on the bottom of the coil, which led to an intermittent misfire.

These cracks can generally be seen if the coil is removed and inspected. The condenser located
next to the coil to aid in suppressing EMI for radio reception fails surprisingly often. Presently, we
disconnect the condenser and throw it out on all high-performance engine installations. Many times
a car has developed a miss, and the condenser had shorted out internally. This can be confirmed
with an ohmmeter, but it just seems easier to eliminate the potential problem from the beginning.
ACCEL offers an improved version EDIS coil to replace the stock unit. It has 10% more output than
the standard coil, and a longer duration arc. Stock coils may need to be replaced/upgraded if they
are more than 5-6 years old, or if the power level reaches 500 hp.
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This has been a sample page from

How to Build Max Performance 4.6 Liter Ford Engines How To Build Max Performance 4.6 Liter
Ford Engines
by Sean Hyland
This revised edition features new and current
information throughout the text, an additional 16 pages,
and all black and white photography.
When the ’96 Mustang came out with the 4.6-liter V-8, some
performance enthusiasts were scared away by its technology. But
those days are long gone. Ford added horsepower and torque to
its 2- and 4-valve V-8s over the years, and the number and
quality of available aftermarket performance parts has exploded.
Ford took things to the next level with the new 3-valve Mustang
GT engine and the 5.4-liter GT and Shelby GT500, adding even
more high-performance options.

In this updated edition of How To Build Max-Performance 4.6-Liter
Ford Engines, Sean Hyland gives you a comprehensive guide to
building and modifying Ford’s 2-, 3-, and 4-valve 4.6- and 5.4-liter
engines. You will learn everything from block selection and
crankshaft prep, to cylinder head and intake manifold
modifications. He also outlines eight recommended power
packages and provides you with a step-by-step buildup of a
naturally aspirated 405-horsepower Cobra engine. This is the
definitive guide to getting the most from your 4.6- and 5.4-liter

Temporarily Out of Stock - More On their way!

Click below to view sample
pages from each chapter.
Chap. 1 - Engine Block
Chap. 2 - Crankshafts
Chap. 3 - Rods
Chap. 4 - 4.6 Pistons
Chap. 5 - Cylinder Heads
Chap. 6 - Int. Manifolds
Chap. 7 - Fuel Injection
Chap. 8 - 4.6 Camshafts
Chap. 9 - 4.6 Exhaust
Chap. 10 - Ignition
Chap. 11 - Lubrication
Chap. 12 - Cooling
Chap. 13 - Power Adders
Chap. 14 - Packages
Chap. 15 - 405HP Engine
8-1/2 x 11
44 pages
445 B/W Photos
Item #SA82P
Price: $22.95
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This is a great book that any modular engine owner or enthusiast will enjoy!

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