January 14, 2003

Step By Step

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0302mm_Ldzoom 2001_Ford_Bullitt_Mustang Front_Side_Burnout
With 265 ponies under the hood, Ford's special-edition '01 Bullitt Mustang GT carries the highest horsepower rating for a 4.6 2V engine. The additional 5 hp (over the base GT engine) comes mostly by way of a special cast-aluminum, high-flow intake manifold. The car came with unique accessory drive pulleys, as well.
0302mm_103zoom 1995_Ford_Mustang_Cobra Underhood_Engine
The 260hp 4.6 SOHC mill found in 99-present Mustang GTs is strong for its size, having a specific output of 56.52 hp per liter. In contrast, the 1995 Cobra 5.0 engine made 48 hp per liter.
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Ford Racing Performance Parts' High-Flow intake manifold kit looks similar to the Bullitt unit, but don't be fooled as they are not identical. The Ford Racing intake (PN M-9424-E46) mates to 1996-98 heads and is designed to out-perform the stock manifold, especially in the 4,000-6,000-rpm range. There are two different installation kits for this intake (M-9444-D46 for 1996-97; and M-9444-E46 for 1998 models).
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Owners of '96-98 4.6 Mustangs can find 35-45 hp by installing Ford Racing's 4.6 High Performance cylinder heads. Designed for use with the Ford Racing High-Flow manifold kit (or a production intake), the heads feature larger valves, increased flow and larger valvesprings to accommodate high-lift camshafts. Note: heads must be used with a Ford Racing High Performance engine management computer.
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When it comes to engine blocks, there are two distinctly different 4.6 iron passenger-car casts and about 10 different cast numbers, even though they are mostly identical in construction. The first iron blocks (1991-92) have cast No. F1AE and have solid dowel pins for the transmission, and the first four main caps are cross-bolted with "jackscrews" between the block and the main caps, but the rear main has no cross bolts. This block was used in 1991-92, and all parts will interchange with new blocks, but the F1AE block is not the best choice for performance applications. The block shown in the photo is a later 1999-up 5.4 Lightning block with cross-bolts on all the mains.
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Modular blocks feature deep skirts and cross-bolts that add strength to the lower end. A bare iron V-8 block weighs 154 pounds. This one is from a Mustang.
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Shown here is an aluminum four-valve block, which will accept 2V heads. Livernois Motorsports fashioned this block with new sleeves that were bored to 3.70 inches. A bare aluminum block weighs just 86 pounds. To make this work, Millen uses custom composite head gaskets and/or copper gaskets on blocks that are O-ringed.
0302mm_109zoom 2001_Ford_Bullitt_Mustang Underhood_Engine
Bullitt Mustangs feature a cast-aluminum intake manifold that is similar to the Ford Racing unit and can be adapted to any '99-up Mustang GT. The Bullitt intake is forged from three individual pieces including an upper plenum, the lower plenum and runner assembly, and a removable panel attached to the underside of the lower plenum.
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One advantage of the Bullitt intake is that it can be ported. Ported Bullitt intakes have shown significant gains in supercharged applications but minimal gains on mildly modified or stock engines. Shown is the lower plenum. It is fed from the rear then the air enters a lower plenum, which feeds the individual runners. These runners cross over the manifold and feed the ports on the opposite side of the engine. Runner length is about 15 inches.
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Looking at the underside of the Bullitt intake, note the rectangular ports that match the port shape on the 1999-up Power Improved (PI) heads. Ford Racing's High-Flow manifold looks similar but has oval-shaped ports.
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All 4.6 2V passenger-car intake manifolds (except Bullitt) look identical from the top, but they are not.
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The 1996-98 manifolds have round ports to match the round ports in the heads.
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The 1999-up intakes have better-flowing rectangular ports to match the PI cylinder heads. These later intakes will bolt-up to the older heads, but a gross misalignment of the ports will result.
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Airflow through the manifold takes this path.
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All 4.6 2V Mustang headers look like this. They are restrictive and should be replaced with tubular-style headers in any performance application.
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Unlike older Ford V-8 blocks, the Modular blocks feature this rear-main seal retainer. "This positively locates the seal and helps prevent premature leaks," says Bob Oster of B&B Performance Machine. Also, notice the Cobra steel crank that was used in this B&B buildup. "All 4.6 cranks are interchangeable, however, some machining is necessary due to clearance problems between the crank counterweights and the main webbing on some blocks," added Oster.
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All 1996-98 passenger-car heads look like this, with rounded or teardrop intake ports and a bridge-type girdle to strengthen the camshaft main caps. Be aware that some PI castings (1L2E) have the bridge-style girdle for the cam caps. These heads were probably used on Explorer engines, from 2001-2002.
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Newer PI heads (1999-present) benefit from rectangular ports and improved combustion chamber design.
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The difference in port configuration is clearly seen in this side-by-side shot. The 1996-98 head is on the left and the new PI head is on the right.
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Earlier heads have an open chamber and heavily shrouded intake valve. The cast piece near the intake valve is called a "swirl fin" and is designed to help the mixture swirl as it enters the cylinder.
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The later PI heads have a smaller chamber and a smaller swirl fin, too. In addition, the intake valve has been relocated closer to the center of the bore to reduce shrouding caused by the cylinder wall.
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All 4.6 2V heads have rounded exhaust ports.
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PI heads have "PI" and "V-8" markings found in the cam/rocker galley.
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All 4.6 engines have hollow camshafts with press-on lobes. You can see that the 1999-up heads do not have the girdle on the camshaft mains. Additionally, some cams have a pressed-on gear, on others the gear is an integral part of the cam, and there are "left" and "right" cams for each engine.
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Modular engines use roller cam followers (or fingers) with small hydraulic lifters. This provides quiet, maintenance-free operation with high-rpm potential.
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One major difference between the Windsor and Romeo 2V blocks is the size of the front cover mounting bolts. Most Romeo blocks take 8mm bolts, while Windsor's take 10mm ones. However, some Romeo blocks did have 10mm bolts.
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Stock Modular connecting rods (except 2003 Cobra) are of the powdered-metal type with cracked caps. Stronger "I-beam" and "H-beam" rods (center and right) are available from Manley Performance. The 2003 Cobra engine gets the Manley units.
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Depending on what year Mod engine you have, you'll find different valve covers that may not interchange from year to year. While the bolt pattern is the same on all passenger-car engines, the covers with the oil fill on the passenger side (shown) will not work with the Bullitt or FRPP High-Flow intakes. We believe these to be 1999-01 valve covers.
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Valve covers with the oil fill on the driver side will work with the Bullitt (or high-flow) intakes and can be found on some 1996-98 and all 2002 engines.
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Livernois Motorsports sells this hot rotating assembly that fits a 4.6 engine. Livernois is currently experimenting with a 3.70-inch big-bore aluminum block with a 5.4 crankshaft destroked to .400 inch. That equals about 344 ci. Dan Millen tells us that the combination will be naturally-aspirated and race only--we can't wait to see it run.
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Companies such as Power Heads Performance sell complete packages to rebuild a 4.6 engine for a high-performance application. These kits generally include a set of ported heads, aftermarket cams, and a Cobra crankshaft.

In 1991, Ford Motor Company quietly slipped a new engine into the Lincoln Town Car to replace the 5.0, and no one blinked an eye. The Mustang GT and 5.0 LX were still powered by the trusty 302, and Ford fans figured it would stay that way forever. However, unbeknownst to Mustang owners, when the boys in Dearborn introduced that new engine, they might as well have announced that there's a new engine in town, it's name is Modular and we're going to stuff it in virtually everything with a blue oval. Amazingly, it's 12 years later, the 5.0 is long gone, and we've come to accept the Modular family of engines in our favorite Fords. It took some time to recognize these "cammers" as true performance engines, but the Modular V-8 has become a real winner, with the latest iterations making close to 400 hp in factory trim.

As we know, the road to the top of the performance hill was not paved with gold, but Modular engines have proven to perform both in Mustangs and in trucks. Unfortunately, those first 4.6 Modular engines ranked low on the performance chart and enthusiasts got a bad taste of this technology. First impressions mean a lot, and, quite honestly, the 215 and 225hp '96-98 Mustang GTs were not Modrific. In fact, most Stang Bangers and journalist-types considered them pathetic. Fortunately, Ford recognized the problem and substantially increased power for 1999.

If there's a downer to the Modular craze, it's that few aftermarket hard parts, such as heads, cams and intakes exist to boost performance, even though the Modular family of engines has been around for a decade. On the other hand, Ford owners looking for extra power can toss on a power adder and find well-over 100 extra ponies. Or, you can find the best factory parts and work them to perfection.

But how do you know which parts to mix and match? What parts will fit, which ones won't? There are many Modular questions so keep reading because in this first part, of a two-part article, we'll find out exactly which parts can be interchanged to make your Mod motor the best it can be. This month, we'll tackle the 4.6 SOHC engine; in the next issue, all your four-valve 4.6 queries will be answered.

A Mod Is Born
Most late-model Ford aficionados mark 1996 as a pivotal year in Mustang evolution because it marked the first time the Modular V-8 was used in a performance application. Some may argue that the '94-95 5.0 GTs were underpowered, but the SN-95 models were superior in ride quality, comfort and handling when compared to earlier Fox Mustangs, and with some simple aftermarket power parts, any SN95 could run with the pack. Then came 1996, and Ford fans watched the beloved 5.0 small-block disappear forever. The replacement displaced a mere 4.6L (or 281 ci). Few considered the "Modular" engine to be a performance V-8, despite the fact that Ford boasted about its many improved traits.

As we mentioned in the opening sentence, the first Mod engine was used in 1991, when a 4.6 SOHC was placed under the hood of the Lincoln Town Car (even though it was designed for front-drive, east-west applications). Shortly thereafter the 4.6 engine was used in the Crown Victoria, Grand Marquis, Thunderbird, and Cougar. In 1993, Ford released the all-aluminum DOHC 4.6 in the Lincoln Mark VIII, which became the predecessor to the Cobra V-8.

The roots of the Modular movement can be traced back to the late-'80s, to a time when Ford was looking for improved engines for its cars and trucks. While the last pushrod V-8 engines of the mid-'90s provided power and reliability, Ford was looking for a way to improve the overall performance of its engine lineup. This meant smoother-running engines with less noise, vibration, and harshness (NVH), better sealing, lower internal friction, along with increased fuel economy, increased longevity, less maintenance and all without sacrificing power. And let's not forget lower emissions. In addition, Ford engineers wanted an engine family that could share machining procedures and tooling as this would reduce costs.

Marketing also played a larger role in the demise of the 5.0 than you would think. Overhead cam technology was perceived to be more high-tech than pushrods, therefore more marketable. With this in mind, Ford started from scratch with a completely new engine design. The idea was that the basic dimensions could be used to build many different engines and power many different vehicles. Thus, the Modular engine was born.

For starters, Modular blocks are cast from iron (or aluminum in the case of the 1993-01 DOHC engines), and they all feature deep skirting with cross-bolted main caps and lots of webbing. Engine accessories are bolted directly to the engine, which makes for smoother overall operation. All cylinder heads are aluminum and have extra-long head bolts that extend below the cylinder bores into the main cap webs to improve cylinder sealing. Naturally, there are no pushrods, but there are hydraulic roller cam followers that are quiet and require no maintenance.

If there is a downside, it is the lack of displacement. Because of its FWD roots, the tight bore spacing severely limits the size of the piston that can be used in a stock block. Intake manifolds are mounted flat so gaskets aren't squeezed out, reducing the chance of a blown gasket.

Taking Shape
Though most folks were opposed to Modular performance at first, we now find lots of people building Modular-powered vehicles. Engine shops are preparing these engines, and customers want the most performance for the lowest price. So now let's take a look at some of the important parts and see what fits.

Modular engines slated for passenger-car use are assembled at the Romeo Engine plant, while the Windsor Engine plant builds the truck engines though some crossover does exist. There are five basic variations of the Modular engine: the SOHC 4.6, DOHC 4.6, SOHC 5.4, DOHC 5.4 (all V-8s) and the 6.8L V-10. All 4.6 engines have a 3.552-inch cylinder bore and 3.543-inch crankshaft stroke, making the engines essentially "square." And while the bore is on the small side, the 4.6 has a favorable rod length-to-stroke ratio. Rather than increasing the bore size, the 5.4 Triton engines gain the extra displacement from a longer 4.16-inch stroke, and the V-10 is essentially a 5.4 with two additional cylinders.

Since 1991, Ford has released many versions of the 4.6L V-8. This means there are different blocks, different cylinder heads, along with some different cams and intakes, too. There are also plenty of interchangeable parts, namely cylinder heads, cranks, and timing assemblies.

"We've been doing a lot with Modular engines lately," says Dan Millen of Livernois Motorsports. "All the [4.6 SOHC] parts fit from year to year, but you can run into a port alignment problem with the 1996-98 parts and the 1999-up parts. That's because Ford changed the port shape from round to rectangular in 1999. We've also found other little things like the PI [Power Improved] '99-up heads look identical to the Lightning heads, but the car heads have nine valve cover bolts and the truck heads have 12. You can use either heads on either engine, as long as you use the right valve covers." Most Modular fans are aware of the difference between the 1996-98 engines and the 1999-up engines. The first Modular engines (1991-98) featured rounded or teardrop-shaped intake ports, and they suffer from intake valve shrouding, and a larger combustion chamber. To remedy the power problem Ford Racing Performance Parts designed a "better" two-valve head with larger ports, reduced intake valve shrouding and a closed combustion chamber. Ironically, in 1999, Ford introduced "Power Improved" (PI) cylinder heads that closely resembled the Ford Racing heads but with rectangular ports and smaller intake valves. The PI heads with matching intake, increased horsepower on the 1999 Mustang GT engine to 260 from its prior rating of 225 in 1998. Any of these heads can be bolted to any 2V or 4V block, as long as the proper intake manifold is used. Keep in mind that putting 1999-up heads on a 1998-earlier engine will increase compression significantly--not a bad thing, but it's something to consider if you're using a power adder.

Millen provided us with cylinder head flow data that shows the improvement in the PI heads is mainly in low- and mid-lift flow, between .100 inch and .450 inch, but the 1996 heads actually out-flow the PI heads (see chart) at .500 and .550 inch.

When building a Mod motor you will need an engine block. We've found about 10 different cast numbers for blocks (from 1991-present), some are better than others. The Romeo plant built the first block, which was the F1AE, and it was used through early 1992. It was replaced by the F2VE casting at the same time Ford released the AODE transmission in RWD cars. This block was superseded by the F4VE, which is identical to the F2VE. All three blocks are virtually the same and have hollow dowels to align the transmission.

The next block in the long lineup is the Romeo-built F65E, but Ford also cast the F6VE and the F7VE. All three blocks are visually and dimensionally the same, have cross-bolts on all five main caps, and were used from 1996-98. There is a threaded hole in the cylinder valley for a knock sensor. These blocks are preferred over earlier blocks and will work in all RWD cars. The Romeo plant also built engines with a F7AE and XW7E casting number. They were primarily used in trucks from 1997-99 but can be used in passenger cars.

Production of the Windsor blocks began in 1996 with the F65E-BB and the F75E. Windsor blocks have cross-bolts on all five main caps and the bolt pattern on the front of the blocks is the same as earlier Romeo blocks. However, some of the holes may be 10 mm instead of 8 mm. This is important if you are purchasing a blower because the compressor bracket attaches to the front cover.

We also spoke with Ralph Pici of Power Heads Performance Inc. who stated, "Any of the two-valve blocks will interchange, but you want to stick with 1996-up blocks because they are the ones using cross-bolts on all the mains. There are differences between the blocks built at Romeo and the ones that come from the Windsor plant. The Romeo blocks have jackscrews that pre-load the main caps and the Windsor blocks use dowels. Both are OK for rebuilding. We've sonic tested a lot of blocks and usually find a wall thickness of .200 inch. The problem is they don't make [head] gaskets larger than .020-inch over so you're limited on how big you can bore the blocks."

We've found that the Modular engine can be built to take the heat of competition or for serious street use. There are dozens of parts but most will interchange. Our best recommendation is to keep as many of the original parts together and document them as you go. The major differences lie in the front covers (8mm or 10mm bolts), the main caps (jackscrews or dowels), and crankshafts. Otherwise it seems all parts can be swapped.

Next month we'll tackle the DOHC, which has more cylinder head options, but fewer blocks.

Basic Modular Engine Dimensions
4.6-liter SOHC and DOHC
Aluminum block weight (bare): 86 lbs.
Iron block weight (bare): 154 lbs.
Assembled cylinder head weight: 44 lbs.*
Displacement: 4.6 liters/281 cubic inches
Bore: 3.552 inches
Stroke: 3.543 inches
Bore spacing: 3.937 inches
Main journal dia.: 2.657 inches
Rod journal dia.: 2.086 inches
Rod length: 5.933 inches
Deck height: 8.937 inches
*Assembled 302 iron head weighs approx. 55 lbs.
5.4-liter (8 cylinders) and 6.8-liter (10 cylinders)
Displacement: 5.4 liters/6.8 liters (330 cubic inches/415 cubic inches)
Bore: 3.552 inches
Stroke: 4.165 inches
Bore spacing: 3.937 inches
Main journal dia.: 2.657 inches
Rod journal dia.: 2.086 inches
Rod length: 6.657 inches
Deck height: 10.078 inches
4.6 Cylinder Head Flow Data
(Courtesy of Livernois Motorsports)
StockPorted
Lift in Inches'96'01'96'01
.1004654 6160
.150 66.67889 86
.20084.598111.5 116
.250103.5119131.3141
.{{{300}}}121.3135146160
.350134.7145 159.6169
.400147156173.3176
.450159.4161185182
.500170166188 185
.550176168192.5186
Part Identification 1996-01**
1996 4.6 SOHC 215HP Mustang Engine
Throttle body: 65mm (2.559 inches)
Intake manifold: composite, cast No. F6ZE-CG
Cylinder heads: cast No. RF-F5AE-AE
Combustion chambers: 49.77cc
Valves: 1.752/1.339 inches
Rockers: roller type, w/1.{{{80}}}:1 ratio
Camshaft lift: .473/.473-inch lift
Compression ratio: 9.30:1
Pistons: hypereutectic w/.153-inch dish
1997 4.6 SOHC 215HP Mustang Engine
Throttle body: 65mm (2.559 inches)
Intake manifold: composite, cast No. F6ZE-CG
Cylinder heads: cast No. RF-F5AE-AE
Combustion chambers: 49.77cc
Valves: 1.752/1.339 inches
Rockers: roller type, w/1.80:1 ratio
Camshaft lift: .473/.473-inch lift
Compression ratio: 9.30:1
Pistons: hypereutectic w/.153-inch dish
1998 4.6 SOHC 225HP Mustang Engine
Throttle body: 65mm (2.559 inches)
Intake manifold: composite, cast No. F6ZE-CG
Cylinder heads: cast No. RF-F5AE-AE
Combustion chambers: 49.77cc
Valves: 1.752/1.339 inches
Rockers: roller type, w/1.80:1 ratio
Camshaft lift: .473/.473-inch lift
Compression ratio: 9.30:1
Pistons: hypereutectic w/.153-inch dish
1999 4.6 SOHC 260HP Mustang Engine
Throttle body: 66.8mm (2.630 inches)
Intake manifold: composite, cast No. XR3E-DC
Cylinder heads: cast No. RFXL3-CZOD
Combustion chambers: 42.40cc
Valves: 1.752/1.417 inches
Rockers: roller type, w/1.80:1 ratio
Camshaft lift: .{{{505}}}/.534-inch lift
Compression ratio: 9.30:1
Pistons: hypereutectic w/.188-inch dish
2000 4.6 SOHC 260HP Mustang Engine
Throttle body: 65mm (2.560 inches)
Intake manifold: composite, cast No. XR3E-DC
Cylinder heads: cast No. RFXL3-CZOD
Combustion chambers: 42.45cc
Valves: 1.752/1.417 inches
Rockers: roller type, w/1.81:1 ratio
Camshaft lift: .505/.534-inch lift
Compression ratio: 9.74:1
Pistons: hypereutectic w/.188-inch dish
2001 4.6 SOHC 260HP Mustang Engine
Throttle body: 65mm (2.560 inches)
Intake manifold: composite, cast No. 1L2E-{{{DL}}}
Cylinder heads: cast No. RF1L2E-6090-D22D (or D24D)
Combustion chambers: 42.45cc
Valves: 1.752/1.417 inches
Rockers: roller type, w/1.81:1 ratio
Camshaft lift: .505/.534-inch lift
Compression ratio: 9.74:1
Pistons: hypereutectic w/.145-inch dish
2001 4.6 SOHC 265HP {{{Mustang Bullitt}}} Engine
Throttle body: twin 57mm (twin 2.24-inch)
Intake manifold: cast aluminum, cast No. RF-2RE3-9A448-AA
Cylinder heads: cast No. RF1L2E-6090-D22D (or D24D)
Combustion chambers: 42.45cc
Valves: 1.752/1.417 inches
Rockers: roller type, w/1.81:1 ratio
Camshaft lift: .505/.534-inch lift
Compression ratio: 9.74:1
Pistons: hypereutectic w/.145-inch dish
**All engine specifications are taken from the NHRA classification guide, found on-line at NHRA.com

Will Fit, Won't Fit
* Blocks--When it comes to 2V 4.6 engines, you'll find there are as many as 12 different castings, but the basic architecture is the same so any heads will bolt up. For performance applications we recommend finding a 1996-up block because these (Romeo and Windsor) have cross-bolts used on all five main caps. Windsor blocks use dowels, and most Romeo blocks use jackscrews; neither have proven to be stronger than the other.

* Ford Racing Power Improved heads (PN M-6049-D46)--will physically bolt to any 4.6 block, but ports are designed to match 1996-98 4.6 intake manifolds or Ford Racing High-Flow intakes. Ford racing heads must also be used with a Ford Racing computer for proper engine calibration.

* Ford Racing intake manifolds (PN M-9444-D46/E46)-- physically fit all 4.6 engines but will only match the cylinder head port shape of 1996-98 4.6 engines. The manifold kit is similar to the Bullitt intake but not identical. Weight is approximately 35 pounds (stock plastic manifold is 15 pounds).

* Bullitt intake--This unit is made of cast aluminum and features a rear inlet and 15-inch runners (stock intake feeds from the top/center and has 17.5-inch runners). The Bullitt intake will fit all 1999-up 4.6 engines, however, there can be some interference problems with the valve covers on 1999-00 engines. Weight is approximately 35 pounds, whereas the stock, plastic manifold weighs 15 pounds. Horsepower increase is minimal on stock or mildly modified engines but well worth the effort on supercharged or nitrous-injected engines.

* Crankshafts--The stock crank in 1991-95 Romeo-built SOHC engines is the F1AE casting that is made from nodular iron. It has six, knife-edged counterweights (the front one measuring .960 to .980 inch), and the flywheel flange has six holes. Beginning in 1996, Romeo engines used a similar crank that carries cast No. F65E. This crank also has a six-bolt flange, but the front counterweight measures .920 to .940 inch. Therefore, you may find an interference problem when installing an F1AE crank in a 1996-up block. All Windsor engines came with the F65E crank, but some had a six-bolt flange, and some came with eight. The most desirable crankshaft is the forged steel unit found in 1996-03 Cobra engines (cast No. F2LE-AG). The Cobra crank can be used in iron-block SOHC engines as long as the eight-bolt flywheel is used (SOHC passenger-car cranks have a six-bolt pattern). Note: Windsor engines may have a different crank (cast No. F65E), which has a smaller front counterweight (.920 inch thick versus .940 inch on the F1AE) so any Windsor engines must be built using the F65E crankshaft or an interference problem may occur between the counterweight and the main area in the block.

* Connecting Rods--All 4.6 engines (except the 2003 Cobra) were fitted with powdered metal rods that have cracked caps. Generally, passenger car engines from the Romeo plant got press-fit piston pins, while Windsor engines got floating pins. Rods can be interchanged, but we recommend using aftermarket steel rods in any performance applications.

* Pistons--Ford used three different pistons in the 4.6 engines. The 1991-99 Romeo pistons have a 10.5cc dish and a 1.5mm/1.5mm/3.0mm ring package, and the pin was press fit to the connecting rod. The 1996-99 Windsor (non-Power Improved) pistons have the same dish and ring dimensions but are of the floating type with circlips holding the pins in place. Lastly, Windsor PI engines have different pistons with a larger (18.5cc) dish to reduce compression, on the PI engines, due to the closed chamber heads. Therefore, it must be noted that a rise in compression (to about 10.5:1) will result when PI heads are installed on a 1991-98 engine.

* 4V heads on a 2V block--This swap is a direct bolt-on, however there are no advantages over using the aluminum block other than availability and/or cost. Note: there are a variety of chain tensioners that may differ depending on where the block was produced.

* 2V heads on a 4V block--This swap is a direct bolt-on. Advantages include lighter weight and ability to replace the sleeves and increase the bore size 3.70 inches.

* Front Covers--Because the Modular engines are used in so many applications, there are quite a few styles of front covers. Passenger car covers differ from truck covers and van covers are similar only to themselves. Likewise, the Mustang covers are different altogether and even from year-to-year. Some covers used 8mm bolts, while others use 10mm bolts. So it's important to keep the cover with the block. When building an engine from scratch, the only way to ensure that you have the proper cover is to trial fit. Then you must be certain that the engine accessories will attach.

* Underdrive Pulleys--Aftermarket pulleys are popular among Mustang owners. The 1996-98 pulleys are of one design, but like most other parts on the Mod engines, they changed with time. Thus, the 1999 design is different, and sometime during the 2001 production run, Ford changed the water pump design again, requiring a different offset in the water pump pulley. Therefore, there are many distinct water pump underdrive pulleys depending on whether you have a 1996-98, a 1999-early 2001 or a late 2001-present engine.