Ford manufactured the modular engine at the Windsor, Ontario; Romeo, Michigan; and Essex, Ontario, factories. All of these plants have different specifications or blueprints and, as a result, the modular engines built at the various factories are often different. To give you an idea of how complex these engines are, here are just a few of the many changes between the Romeo and Windsor SOHC engines:
• Valvecover bolts: Romeo blocks use 11 bolts to hold the passenger-side valvecover; Windsor blocks use 14.
• Main caps: Romeo early blocks use a smaller main bearing than Windsors. The Romeo uses a single thrust washer; the Windsor uses two thrust washers. Early Romeo blocks used a jack screw between the main cap and side skirt; Windsors used a dowel system. In 1999 Ford began eliminating the jack screw system in favor of interference-fit main caps on some blocks.
• Crankshafts: Windsor blocks use six bolts to hold the flywheel or flexplate to the crankshaft. Romeo can be either 6- or 8-bolt depending on application. Most performance engines use the 8-bolt crank.
• Connecting rods: Windsor pistons use a floating pin; the Romeo is a press fit pin.
• Camshaft sprockets: Windsor is a press on; Romeo uses a bolt and spacer.
As you can see, it can be difficult to interchange parts between assembly plants.
If you are not purchasing a crate engine or buying from a known source, it’s important to be able to identify what engine you are contemplating. Ford has not been particularly consistent in its means of identifying the modular engines through the years, and what works with some engines doesn’t work with others. An engine cobbled together by someone unfamiliar with the platform can end up an expensive boat anchor. In the end, if you can’t identify the engine, walk away from the deal.
If you are looking at a complete donor vehicle for your swap project, two pieces of information from the Vehicle Identification Number (VIN) help you figure out what you have and what you need. The first is the 8th digit of the VIN that specifies the engine installed in the vehicle. The second is the 10th digit that denotes the model year of the vehicle (not the year it was built). The VIN is found on the plate under the front windshield on the driver’s side of the dashboard, or on the door sticker.
If you are looking at a complete donor car or are shopping for a used engine, the vehicle VIN sticker in the door tells you a lot about the engine and drivetrain. The 8th digit of the VIN is the engine, and on this 2010 Mustang it is an “H,” which is a 4.6 3V engine rated at 315 hp. The 10th digit tells the year of manufacture, here an “A,” which stands for 2010 (note the car build date noted in the upper left-hand corner is 09/09). The transmission is denoted under TR as “K,” which denotes a Tremec TR-3650 5-speed.
These charts list the engine codes for modular engines 1991–2015. The key is as follows: SOHC = single overhead camshaft; DOHC = dual overhead camshaft; 3V = three valves per cylinder; C/R = 2000 Cobra R; R/A = Mach I Ram Air; GT = Ford GT supercar; S/C = Supercharged; B = Boss; FF = Flex Fuel; R = Romeo engine plant; W = Windsor engine plant; E = Essex engine plant; RA = F150 Raptor; CNG = compressed natural gas; NGV = natural gas vehicle; LPV = liquid petroleum vehicle; GFP = gaseous fuel prep
This breakdown shows the year digit, which is in the 10th position of the VIN. Ford used a letter at the end of the 1990s, switched to numbers for the 2000s, and then back to the beginning of the alphabet for the next decade.
The sequence of engine codes for modular engines from 1991 to 2015 was not consistent with letters and numbers, and used the same designators in different years. In some cases, within the same year the code could be for either a 6-cylinder or a modular engine, depending on the vehicle. The horsepower ratings also varied over the course of the engine series build, so it is provided here as a range. Finally, a W-code engine in a Crown Victoria and a Ford F-150 may have come from the same plant (Romeo, Michigan), but have different components mounted on it, such as intake and exhaust manifolds.
The 10th digit designates the year the engine was manufactured. Because of the many running changes in the plants, this may be helpful to you and your engine builder when searching out performance or replacement parts if needed.
The next level of engine ID is the engine tag. The engine tag includes information on engine calibration, date of manufacture, and assembly plant. Ford’s method of identifying engines varied in style and location. Some of them are stickers, others ink. It is possible that they can be switched or fade over time, so the identification of an engine can become difficult. Here are some of the ways to identify an engine.
Ford used primarily vinyl stickers to denote its engines through the modular engine years. The calibration code 2G839AA denotes this engine as a 2003 Cobra supercharged engine. The build date is noted as August 13, 2002, and it was built at the Romeo Engine Plant (REP). This sticker is located on the passenger-side valvecover at the bottom middle of the cover. A similar sticker is located on the driver-side valvecover, but only has the engine calibration code, date of manufacture, and a large bar code.
Ford has stayed fairly consistent with the base specifications of these engines, with only a few custom setups.
Although at least a half dozen displacements exist for the modular engine, the base dimensions are one of the more constant parts of these engines. All the engines share the same bore spacing at 100 mm (3.937 inches), except for the 6.2 engine. The two standard block deck heights are the taller 5.4 and 6.8 V-10 at 256 mm (10.079 inches), and for all of the smaller engines, 227 mm (8.937 inches). The 5.8 was slightly shorter at 225.7 mm (10.0673 inches).
But there are variations within variations. The 6.2 Boss SOHC shares many of the engine features of a typical modular engine, but it has a wider bore spacing at 115 mm (4.53 inches) and a unique deck height at 239 mm (9.41 inches). This allows for bigger volumes than the standard modular engine platforms. The Triton 6.8 V-10 is