Jim Smart
February 13, 2014

When Ford introduced the all-new 4.6L single overhead cam V-8 in the Lincoln Town Car in 1991, many were underwhelmed. A 281ci cammer in a fat overstuffed Lincoln? Many people saw the new Modular V-8 as an engine that could never be built for performance use, nor could it keep up with the pushrod classics like the small- and big-blocks. It wasn't the end, but instead, the beginning of a new era of powerful low-displacement Ford V-8 screamers leading up to the hot 5.0L Coyote V-8 20 years later.

What most lacked in 1991 was an understanding of Ford's new overhead cam V-8. If you've never been intimately involved with the 4.6L and 5.4L Modular engines, they're intimidating. Pop the cam and front timing cover and the Modular mill is a confusing series of chains, guides, and valvetrain components. It is surely large. Pull the comparatively large SOHC heads and it is smaller than your 5.0L High Output small-block. Though it consumes a lot of space, the Mod' is also long on potential, durability and power.

Before you can build the Modular, you've got to understand the Modular. This is not an engine forgiving of error, even small ones. If you approach this engine sans proper understanding, it gets costly and time consuming. The objective of this article is to help you get it right.

The Modular overhead cam V-8 combines a number of great attributes from past engines. The Modular block is skirted like an old FE or the Y-block; it is cross-bolted like the legendary 427, yet compact like a small-block.

From a more traditional standpoint, the Modular's bore and stroke don't make much sense. The 4.6L is a "square" engine with a 3.552-inch bore and a 3.543-inch stroke configured on 3.937 bore spacing. Take the same 3.552-inch bore and add a little more than one-half inch (0.622-inch) of stroke to 4.165-inches and you have the 5.4L engine. The down side to both Modular engines is the dynamics of these bore/stroke combinations. They do not make good low-end torque. These are engines that like to rev with peak torque coming in higher than traditional Ford V-8s.

Modular Timeline

When the 4.6L SOHC Modular V-8 was introduced, it was a standalone engine built in one engine plant—Romeo, Michigan—the former Ford Tractor division factory left empty when Ford sold the division to New Holland. In the beginning, the Modular V-8 was simple to understand because there was one plant and one basic 4.6L SOHC engine. The 32-valve 4.6L DOHC came next for 1993 in the Lincoln Mark VIII; also produced at Romeo.

When the Windsor, Ontario engine plant began building the 4.6L and 5.4L SOHC engines in 1996, mostly for trucks and sport utilities, this engine family became more complicated with the two plants generating engines with slightly different architectures. You'll want to be aware of the varied differences among the Modular engines when planning your engine build; Romeo and Windsor engines are different, with minimum interchange of parts.

1. Head on, the 4.6L SOHC engine is expansive and to some degree, intimidating. It is wider than the Boss 429 and on a par with the vintage 427 SOHC in terms of size. It requires a wide engine bay. If you’re planning a Modular swap for your Mustang or Fairlane, plan on shock tower modification or elimination, because it will not clear the towers. This 2V SOHC Modular is missing its induction system, which is either cast-aluminum long runner (trucks) or plastic short runner (cars)
2. This is the 4.6L Modular short-block minus cylinder heads. When you study this engine’s architecture, you find incredible ruggedness in its cross-bolted and skirted design with a lot of webbing, which is where its strength comes from. The Modular V-8 is a new generation of Ford engineering mindset. Ford spent a lot of money developing the Modular V-8 and fully intended for this engine to be in production for decades and across several car and truck lines. Because millions of these engines have been produced, there are a lot of cores out there to build from. Ford continues to produce new block and head castings, which are available through Ford Racing Performance Parts and its dealers.
3. Head on, the 4.6L Romeo block looks like this. A lot of them have the “R” indicating a Romeo block, which is different than a Windsor block, and very little is interchangeable. The Romeo block has jackscrew cross-bolted main caps.
4. Side by side are the 5.4L SOHC block (left) and the 4.6L block (right). The 5.4L engine is Windsor-only with a taller deck than the 4.6L. The 4.6L engine was produced at both Romeo and Windsor, but with different nuances you need to be aware of. Look for the “R” on Romeo block, though not all will have it. Windsor blocks have a “W.”
5. This is the bottom end of a Windsor block with dowel style cross-bolted main caps. These dowels provide support between the main caps and the block. Cross-bolts pass through each dowel.
6a. Romeo 4.6 blocks have internally threaded, jackscrew-style main caps. Once the main caps are properly torqued, jackscrews are threaded out to where they touch the block skirt, and then bolts are installed and torqued using sealer under the bolt head to prevent oil leakage.
6b. Where the Windsor block differs is dowel pins that wedge into place once main caps are torqued.
7. This is a 4.6L Windsor block with dowel-style main caps. Think truck when you think of the Windsor engine plant. Engineering is angled with rough duty in mind. The strongest iron blocks are from the Windsor foundry and plant. The dowel pins support the main caps and are driven in with a mallet. Once seated, install the cross bolts and torque to Ford specifications.
8. Where Modulars differ from FE, Clevelands, and small-blocks is a shim-style thrust bearing at the Number 5 main cap. Shims are of varying thicknesses to get just the right crankshaft endplay. Having the thrust at Number 5 is a GM nuance, which makes it odd in the Ford camp.
9. According to author George Reid’s excellent How-To Rebuild 4.6L/5.4-Liter Ford Engines book from CarTech Books, all SOHC Modulars have cracked powdered metal connecting rods with cap screws. Though powdered metal sounds wimpy, it is actually a strong connecting rod that will take up to 500 horsepower according to Reid, though it is suggested you opt for a good Manley rod if you’re going above 450 horsepower. Most of this decision is centered on how hard you intend to run your engine and for how long.


Boss Block

If you're going to build a 4.6L low-deck engine from scratch, begin with either a new Romeo off-the-shelf block or the 5.0L iron BOSS block (M-6010-BOSS50) from Ford Racing. This BOSS50 block, which is cast at the Cleveland foundry, has the 4.6L deck height and 94mm cylinder bores along with 17mm minimum main web thickness. Main caps are interference fit void of jackscrews and dowels. Though the 4.6L Romeo and Windsor blocks are rugged, this one you can really put to the test. Engine mount bolt patterns are 4.6L iron block style. An adaptor plate is available if you intend to use this block in a 3V aluminum block application. You can lasso the BOSS50 block for about $1,369 plus shipping, handling, and taxes.


Reciprocating Parts

10. The Modular’s oil pump is crank driven, which makes it decidedly different than your vintage V-8. Oil pump installation calls for perfect centering of the pump on the crank before tightening bolts. The pump cannot sit on the crank or be offset in any way. If it does, pump damage and failure will result. Run the DOHC/Cobra high volume pump (F8OZ-6600-AA). Some pick-up modification is required when you run this pump. Melling offers a high-volume steel billet pump for Modular engines (#10227) as does Ford Racing (M-6600-D46), which includes the pump and pick-up.
11. Here are the two factory oil pumps side by side. According to George Reid’s 4.6L/5.4L book, the high-volume Cobra/DOHC oil pump is the pump of choice for your SOHC. As you can see the Cobra pump has larger passages yielding higher volume, but not higher pressure. You will need to perform pick-up modifications to install this pump on a SOHC engine.
12. Reluctors and gears changed in 1996. On the left is the ’91-’96 thick steel reluctor (trigger wheel). On the right is the ’96-up thinner stamped steel reluctor and crank gear with a space to make up for the difference in reluctor thickness. Although there has been some confusion on which way the stamped reluctor teeth face, it is always toward the timing cover and away from the engine block. Point these teeth toward the block and you will experience engine damage due to teeth and chain interference.
13. Another great advance in the 20-year-old Modular engine is its lightweight valvetrain consisting of stamped steel roller cam followers and compact hydraulic tappets (lifters/followers), downsized valves and springs, and composite cam technology—no pushrods to fumble with here. The Modular’s overhead cam design eliminates the excess of overhead valve/cam in block mindset. Roller technology reduces internal friction.
14. The Modular’s composite cam with larger swaged-on lobes for reduced friction yet with a more aggressive profile. It is the larger lobe that allows the roller rocker to navigate the lobe more smoothly and with less friction. Note there are no cam bearings. Cam rides directly on the journal with an oil wedge to carry the load.
15. This is a Romeo non-PI (Performance Improved) head (prior to 1999) with the comma-shaped intake ports. Romeo SOHC heads have this cam girdle as well.
16. This is the Romeo non-PI head 51cc chamber. The smaller 42cc PI chamber offers improved high-swirl performance and greater compression ratio for more power.