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4.6L Camshafts and Valvetrain
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The most distinguishing feature of the 4.6/5.4-liter engine family is the overhead camshaft
arrangement. This provides the advantages of OHC geometry, and gives the cylinder-head
designers more latitude, since they don’t have to work around pushrod placement. It is interesting
that Ford chose to use a roller camshaft follower rather than the more widely used camshaft bucket
follower, but it does have both it’s advantages and disadvantages, as we will see.
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Camshafts
The camshaft provides yet another area of this engine for Ford to showcase new technology, in this
case with the construction method of the camshaft itself. The lobes are formed of powdered metal,
very close to the final shape desired. There are serrations on the inside bore of the camshaft lobes
that lock the lobe in place on a hollow tube that forms the shaft.
When all the lobes are in the proper location, a ball is drawn through the tube, which locks the
lobes in place. At this point, the lobes receive grinding to finish the shape, the journals are ground
and polished, and a new camshaft is born. This method of camshaft production is proprietary, and
is more cost effective than other methods of production. The result is a lightweight, durable
component with very few field-service problems.
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On high-mileage 2-valve cars such as police vehicles and taxicabs, cracked lobes are sometimes
seen. I do not know the exact reason for this, although heat and a lack of timely oil changes could
be contributing factors. Even though the lobe has cracked, the owner may not be aware of the
situation. There is usually no noticeable noise or loss of performance to suggest a problem exists.
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Unique to the production camshaft
is the manufacturing method. The
powdered-metal lobes are located
on the shaft with serrations. A ball
is drawn through the tube to
expand it, locking the lobes in
position. The camshaft is then
finish-ground and polished.
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Assuming the camshafts are not cracked, if the cams are to be reused on a rebuild, I would polish
the journals and lobes with a piece of 400-grit polishing tape. The cams should turn easily in the
cylinder heads. If there is any tightness or binding, the cam journals need attention. Because the
camshafts ride directly on the aluminum journals, any loss of oil pressure will show up on the
camshafts first. Without oil pressure, the camshaft will pick up aluminum material from the cam
bores very quickly. I have seen engines seize the camshafts in one or more positions, yet the
crankshaft bearings show no signs of distress.
The clearance between the camshaft journal and the camshaft should be .001 inch minimum to
.0025 inch. If the cams turn tightly in the bores, and there is no material pickup on the cam journals,
we will hone the ID of the cam bores. This is done in the same machine that is used for line honing
a block. If the bore is extensively damaged, first a cut is taken from the mating surface of the cap on
the milling machine, much the same as the cap grinder works on the block main bearing caps. A
similar cut can be made on the top of the cylinder head if required.
The camshaft caps are then torqued in place, and honed with a special tool to the correct
dimension. The honing process has the advantage that it trues the cam bearing bores in relation to
each other, in addition to creating a round hole of the desired diameter. Should the cam bearing
bore be severely damaged with a lot of material removed, normally, we would scrap the head. If this
was an expensive race head with many hours of preparation, the bore could be built up with
welding, machined close to desired size on a mill, and honed to finish size. In the case of a stock
head, it would be more practical at that point to purchase a new head.
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Previously, we had tried cam bearing inserts for repair of damaged cam bores, but found that the
bearings were time consuming and fussy to install, and they did not work all that well. The bearing
insert could not be trued to the other cam bores, and the bearing insert relied on a small tang to
prevent rotating in the bore. Use on a few race engines showed that the bearings would try and
spin if the lubrication was marginal, and the wear patterns indicated that the bearings were not
always square or concentric in their installation. I think the current method we use is the best overall
solution.
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Performance Camshafts
Performance cams for the modular engines can be produced two ways. One method is to regrind
the stock camshaft; the other is to use a new billet core. Originally, regrinding the 4-valve cams was
the only way to go. I spoke to several companies until I was blue in the face regarding the
manufacture of billet blanks for both the 2-valve and 4-valve engines. No one was interested in
tooling to produce blanks. Crane made some 2-valve billet blanks for Ford Motorsport a long time
ago, but they only made 50 sets, and when they were sold out, Ford discontinued the part. I think
we purchased 40 of those 50 sets at the time.
Anyway, regrinding of the 4-valve cams has been a viable option since the beginning. The base
circle diameter is reduced through the grinding operation, and the valvetrain must be adjusted to
compensate for the reduction in the base circle. This can be accomplished one of two ways. A
hardened washer can be placed under the valve lash adjuster (lifter) or a longer valve stem can be
used. The objective is to retain the same amount of lifter preload as the original camshaft geometry
provided.
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Billet 8620 steel
blanks are presently
available for both
the 2- and 4-valve
camshafts. The billet
blank comes with a
semi-finished lobe
that is finish ground
to desired
specifications.
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Grinding the 4-valve cams requires a lot of coolant and a slow feed rate on the grinder.
Experimenting with grinding wheels helped us find a combination that works well. If not enough
coolant is used, or the feed rate is too high, overheating at the point of grinding contact will occur,
and the lobe will crack. Once the lobe has cracked, it is best not to use the camshaft. The
powdered metal lobes are induction hardened at the factory, and are very hard, so care must be
exercised. The hardening is quite deep, so there is no concern over grinding down past the
hardening. In fact, I can say that we have never seen a soft lobe on any 4.6 cam, new or reground.
For most of our profiles, the base circle will be reduced from the original 1.900 inches to 1.800
inches. This has the added benefit that the roller speed is reduced on the follower, with less
distance to travel around the lobe.
So, regrinding of the 4-valve camshafts worked out, now onto the 2-valve cams, right? Wrong. For
some reason, regrinding the 2-valve cams has never worked properly. Whereas the 4-valve cams
would only crack if someone got too aggressive in the grinding process, the 2-valve cams would
crack afterwards, sometimes weeks or months later, or sometimes just sitting in the box on the
shelf. I have no reasonable explanation for this, but my theory is that for whatever reason, there is
more stress built up in the 2-valve lobe, and grinding a new profile just creates a place for the
stress to relieve itself by cracking the lobe. It is possible that the force exerted on the lobe is higher
during the manufacturing process. You would think that the two types of cams would be similar, but
they most definitely are not.
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So, the net result of all this is that I can recommend regrinding the 4-valve cams, but not the 2-
valve cams. Until quite recently, this created a problem, because there were never enough 2-valve
billet blanks available to satisfy demand. And since I could not interest anyone in tooling up to
produce more, the supply/demand relationship was out of whack for quite some time.
Fortunately, this has turned around recently, and billet blanks are now available for both 2-valve
and 4-valve engines. The billet cores are manufactured from 8620 steel and rough profiled on a
camshaft mill. The billet cores are heavier than the stock cams by a significant margin (7.5 lbs vs. 5
lbs), since they are solid through the center, not hollow like the OEM camshaft. This poses no real
problems, except for very high-end road-race and drag 4-valve engines where rotating mass is
minimized. In this case we gun drill the blank, prior to grinding the profile.
All billet blanks are produced with a 12-mm threaded hole for the cam-gear bolt. Ford has used 12
mm, 10 mm, and even some pressed-on designs. This requires that the billet cams be installed with
new gears and hardware on some model years.
‘93-‘97 4-valve engines can use the stock gears and bolts, but ’98-up engines require the old-style
gears. ‘92-‘98 2-valve engines can use the stock gears with aftermarket cams, but ‘99-up engines
require new gears and hardware.
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Camshaft Selection
The 2-valve and 4-valve engines are two different animals in respect to camshaft design. The 4-
valve engine does not require as much valve lift to achieve high flow rates, because the curtain
area of the valve is the limiting factor to flow. The curtain area of a 4-valve design is much larger at
lower valve lifts than a similar 2-valve design. As the drawing shows, a single intake valve would
require a valve lift of .821 inches to match the valve curtain area of the 2 smaller intake valves in a
4-valve design with only .500 inches of lift. This, in a nutshell is the 4-valve head’s advantage. To
achieve over .800 inches of lift on a 2-valve design requires some very exotic valvetrain
components, where achieving similar flow potential with a 4-valve head can be achieved using
mostly production pieces.
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2-Valve Cams
The stock ‘92-‘98 2-valve camshaft provides .480 inches of valve lift with the production 1.79:1
rocker-arm ratio. The valve duration at .050 inches of lift is 204 degrees on the intake and 208
degrees on the exhaust. In 1999, the power improved heads were released into production, and the
camshaft specs changed. Valve lift went up to .535 inches on the intake and to .505 inches on the
exhaust, with duration dropping to 192 degrees on the intake, and 184 degrees on the exhaust.
The combination of more lift and less duration adds low-end torque. A good improvement on an
early engine would be the substitution of the PI camshafts for the early ones, along with some
cylinder-head work to realize the potential of the cams. They are available under part number XL32-
6250CA/AA, and YF72-6250-BA/AA for the pressed-on gears.
Mild street engines with bolt-on parts can benefit from a profile with 205 to 210 degrees intake
duration, and 200 to 205 exhaust duration. Valve lift up to .550 inch would be desirable. The
challenge with increased valve lift on the 2-valve engine is the lack of a quality valve spring on the
market at the present time, a subject we will deal with more later in this chapter. At this point,
however, a lift up to .550 inch is achievable with a stock spring.
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When installing billet
camshafts in a Windsor
engine, bolt-on style cam
gears, along with
spacers, bolts, and
washers are required.
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Testing we have done so far indicates that the intake manifolds presently available do not offer
enough flow potential to exploit valve lifts over .550 inch at this time. If a custom sheet-metal intake
were used, that situation might change, but at the present time, most of the high-output 2-valve
engines rely on forced induction, and we can get dramatic improvements just by holding the valve
open longer. We have a 2-valve grind with .500 inches of lift and 230 degrees duration at .050 inch
on both intake and exhaust. This camshaft will produce 350 hp on a 2-valve naturally aspirated
(NA) engine with good exhaust and intake potential.
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Windsor engines use
the pressed-on
camshaft gear, where
the Romeo engines
use a bolt-on gear.
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The same profile will add over 50 hp on a supercharged 2-valve engine with 10 lbs of boost. And
because the lift is only .500 inch at the valve, it can be used on any model year engine with stock
springs. The idle is a bit choppy with this much duration, and the power comes on sharply at 3000
rpm, but it is an excellent hot-street or street/strip camshaft. The power continues up to 7000 rpm,
which is the limit of the valve spring. The middle ground would be a profile with 215-218 degrees of
duration at .050 inch valve lift, and again .550 gross lift. I expect a great deal more development on
2-valve camshafts in the next few months, as we, along with Comp Cams, Crower, and Crane, work
to provide more selection.
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4-Valve Cams
The production ‘93-‘98 4-valve camshafts have a 3-degree offset ground into the intake lobes.
The primary port lobe opens sooner than the secondary port does, presumably to try and
produce some swirl motion in the chamber. This is too difficult to reproduce on the cam grinder,
and we and every one else grind both intake lobes in the same phase. The nice thing about the
4-valve camshafts is that we can mix and match profiles easily, and the centerlines of the cams
can be readily adjusted to obtain the desired characteristics. There are several profiles we have
used with the 4-valve heads.
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The ‘93-‘97 4-valve engines use a
separate camshaft key to locate
the cam gear during assembly, as
shown on left. The cam gear was
produced with a corresponding
keyway. In 1998, the factory
changed to a cam gear with an
integral key. The slot milled into
the camshaft was changed to
accommodate the integral key. If
an early camshaft is used with a
late cam gear, interference
occurs. The answer is to file the
integral key, or to use the early
cam gear.
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A good cam for mild street applications has 209 degrees of duration at .050 inches of valve lift, with
.452 inches of gross lift. This camshaft will meet state emissions tests, and has a smooth idle
quality. Next up is our blower camshaft, which uses the same intake cam, but substitutes a
225-degree duration, .452-inch lift exhaust cam. With forced induction, we try to add at least 10
degrees more duration on the exhaust profile than the intake carries. On an NA application, the
stage-2 intake camshaft has 235 degrees duration at .050 inches of valve lift, and .472 inches of
gross lift. The exhaust cam goes to 225 degrees of duration, with .452 inches of gross lift. Stage-3
cams are simply the 235-degree cams in all locations.
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‘93-‘00 4-valve engines
used a 12-mm camshaft
bolt as shown on the right.
In 2001, a 10-mm bolt was
substituted for the larger
version. The 12-mm bolt
would be preferable for
race engines.
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Previous | Next
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This has been a sample page from
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How To Build Max Performance 4.6 Liter
Ford Engines
by Sean Hyland
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This revised edition features new and current
information throughout the text, an additional 16 pages,
and all-color photography.
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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
Ford.
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Click below to view sample
pages from each chapter.
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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
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445 Color Photos
Item #SA82
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This is a great book that any modular engine owner or enthusiast will enjoy!
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Other items you might be interested in
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