This chapter focuses on the foundation element of an FE Ford engine build—the block itself. The FE engine was in continuous production for roughly 20 years, so there are a lot of engine blocks in cars, garages, and junkyards. As the popularity of the FE engine has re-emerged, it seems that every one of these has magically become a 428 Cobra Jet, a Shelby part, or a “survivor” of some sort, even if they started out powering an F-150. While the focus of this book is performance building and not “numbers matching,” a certain amount of detective work is mandated when embarking upon any FE engine project.
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FE Block Architecture
All FE engine blocks share many common design features, which serve to separate them from the other Ford V-8 engine families:
- 10-bolt cylinder-head pattern using 1/2-inch fasteners
- 10.17-inch deck height as measured from the crankshaft centerline to the cylinder head mounting surface
- 4.630-inch cylinder bore spacing
- Deep-skirt “Y”-block design where the oil pan rail completely encases the crankshaft and mainbearings
- Unique bellhousing pattern that isn’t shared with any other Ford engine
- A 2-bolt motor-mount pattern for pre-1965 blocks
- A 4-bolt mount pattern for later blocks, which can be retro-fit into earlier applications
The Blocks: Identification and Application
Ford FE engine blocks used for performance builds are generally selected from one of three groupings: 390, 428, and 427. While other blocks are out there, these three are the foundation for the vast majority of high-performance street and track applications.
The 390-based blocks, which have an original bore diameter of 4.050 inches, are by far the most plentiful. These were in production from the late 1950s through the middle 1970s, with the majority being used in large passenger cars and pickup trucks. The common 360 engine also utilized the 390 block, with no difference in features or markings, as did the 1966 410 Mercury. The blocks from medium-duty trucks are very similar to the 390 block, and are referred to as 361 or 391 engines. The medium-duty truck blocks have a larger distributor shaft hole, requiring a bushing for passenger- car use.
There are several differences in 390 engines from various years and applications. Perhaps the most obvious variance is the use of a double or reinforced main web design on the heavier-duty versions of the block. Most of the “mirror 105” blocks (see the casting information that follows), as well as the 361 and 391 medium-duty truck blocks carry this feature. It can also be found almost at random on other engines. If you have your choice, it’s probably the better piece, but the benefits are modest at best.
The 428 blocks, used in numerous Galaxies, Thunderbirds, and high-performance Mustangs and Fairlanes, are far less common than the 390. These blocks are the basis for the famed 428 Cobra Jet engine and use a 4.130 basic bore dimension. Many 428 engines were also used as industrial and irrigation power plants. The Cobra Jet and industrial blocks usually have the double main webbing.
The rarest and most desirable of the FE blocks is the revered 427—with either center oiler or side oiler. With a base bore diameter of 4.233, this was the basis for the engines found in cars such as the Thunderbolt or the NASCAR program. Most–but not all–427s have screw-in-type core plugs, a feature not found on any other FE engine.With very few exceptions, 427 blocks have cross-bolted main bearing caps, using 3/8-inch fasteners through the sides of the block to add significant strength to the FE bottom end. The center-oiler design uses the same lubrication strategy as that employed in more common FE engines, while the side-oiler design has a unique main-feed galley along the side of the block (hence the name). Side oilers can be said to prioritize main and rod oiling, with upper-end lubrication being transferred through grooved camshaft journals (more on this later).
Most 427 blocks were used in high-performance passenger cars and were never produced in large volumes. Many others can be found in marine applications, but rarely in industrial engines. Brass-core plugs usually identify a 427 as a marine engine. Earlier 427 engines were all equipped with solid lifters, and have no provisions for lifter oiling; conversion for hydraulics is possible, but difficult and expensive. Many of the service blocks, the few used in the 1968 Cougar GTE, and the marine blocks usually have hydraulic-lifter oiling provisions. In addition, many marine 427s are cast as side oilers but drilled as center oilers.
External Identification: How Can You Tell What You’ve Got?
The short answer to this most frequently asked question is: You can’t, at least not from the outside of an assembled engine in the car. All FE engine-block castings appear nearly identical, with the notable exception of the side-oiler passages and cross bolts above/along the oil pan rail on many of the 427s. It takes a highly trained eye to notice the small cues that define a high-value part from the mundane. And even the best parts scrounger often cannot make a positive identification from markings alone on an assembled engine.
A good place to start your identification search, and a way to eliminate certain possibilities, is with the casting marks on the block. FE engine blocks usually have several casting numbers, both formal and sand scratches, on various areas of the block. Some of these marks are good for identification, but unfortunately many other markings were used almost at random and have little if any meaning for actual identification. I’ll cover the most common ones below, but remember that nothing on an FE can be taken for granted. There are actual noncross- bolted 427 industrial engines as well as paper-thin 390s sold as standard-bore 428s online. Take nothing for granted.
Mirror 105: Just like it says: a backward mirror image number “105” casting mark commonly found on the driver-side front face of blocks cast at Ford’s MCC foundry starting somewhere in the early to mid 1970s. It’s usually, but not always, a later-model 390 block with the extra main webbing.
352: The 352 designation is found on the driver-side front face of many of the FE blocks cast at Ford’s Dearborn Iron Foundry (DIF) throughout the 1960s. This does not mean you have a 352 engine, or anything else for that matter. Most 390 and 428 engines, as well as many 427s, have this marking.
66-427: This one is often found on the inner valley above the lifters or on the bellhousing face. It tends to get folks really excited for a few minutes, but it means pretty much nothing. It’s often found on otherwise normal 390 engines.
C Scratch: This is a good one to find. Found as a freehand letter “C” scratched in the bellhousing area of the block, this is considered a good indicator of the double-webbed 428 CJ block.
A Scratch: Another one that’s nice to find. This is the letter “A” freehand scratched into the bellhousing area casting and normally associated with non-CJ 428 engines.
Inside the Water Jackets: Proof positive of a 428. If you remove the center freeze plug, you can often see the number “428” cast right into the base of the water-jacket core. You can also find similar casting identification by looking straight down through the water opening on the decks where the head gaskets go— you’ll need a flashlight.
Casting Numbers, such as C6MAxx: These numbers are normally found cast upside down below the oil-filter-mounting pad. Unfortunately, they don’t really mean all that much. While important for a restoration project, the fact is that Ford used the same casting number across a wide variety of engine sizes and levels. That means that these numbers do not help for identification other than for exclusion. You know that a D4TE (the “D4” indicates 1974 in Ford code) is not going to be a 352, which was discontinued in 1966.
Date Codes: Often, but not always, cast in place alongside the casting number, the date codes tell you when the block was made. Like the casting number, these do not tell you anything about the engine itself other than by exclusion; i.e., a block cast in 1964 is not a Cobra Jet since those started in 1968. Date codes are the “holy grail” for restoration work, but they have limited value for performance efforts.
Cross Bolts: It’s most likely a 427, unless a racer or hot rodder has added them sometime in the block’s history.
Screw-in core plugs: Most often indicates a 427, unless a racer or hot rodder has added them sometime in the block’s history.
The “Drill Bit Test”
This one test is the single best way to quickly identify an assembled FE block, and credit for it goes to FordFE.com forum member David “Shoe” Schouweiler. You only need the simplest of measuring tools– some drill bits. The following is paraphrased from several of Dave’s responses to block identification questions posed on the forum.
Remove the center freeze plug from the side of the engine block. Using common drill bits, then slip the shank portion of the largest possible bit in between the center cylinder cores through the freeze plug opening. The size of this largest drill bit indicates which water-jacket core was used to cast the block.
If you can only fit a 1/8- or 9/64- inch drill bit shank between the cylinders at the largest gap position on the block, and a 10/64-inch bit doesn’t fit anywhere, then they are 427 water jackets.
406/428/DIF361/DIF391 blocks allow a 13/64-inch drill bit shankto fit into the gap at the largest position.
MCC361FT/MCC391FT blocks (MCC = “mirror 105” marking) allow a 14/64-inch bit to fit between the cores.
Regular 360/390/410 blocks hang around the 17/64- to 19/64-inch water-jacket space at the largest position on the block.
These are only approximations, but tend to be close.
Even if you do have the good jackets, be sure to sonic map the cylinders before boring. If the core has shifted, it could cause problems. It is not at all unusual for FE engines to have considerable core shift. And the oft-raced and abused 427 engines seem to have some of the thinnest cylinders. A block with core shift has cylinders that are thicker on one side and thinner on the other. This can leave the cylinder wall too thin after machining, compromising strength and piston-ring seal.
The New Blocks: Aftermarket Offerings
The FE engine’s recent renaissance has fostered considerable interest from the automotive racing aftermarket. Among the new FE parts now available are several brand-new engine blocks from, in no particular order, Dove, Genesis, Pond, and Shelby.
Most of my personal experience has been with the Genesis and Pond offerings. Thus, they are covered here in detail. Any of these blocks are considerably stronger than any factory parts.
The factory 427 engines can be identified by their unique crossbolted main caps, which have small spacers. These spacers are unique to their position and reside between the oil pan rail and the cap. The aftermarket block suppliers have taken this a step further by integrating the spacers into the main caps themselves. On the Genesis blocks, the spacers have a protruding flat section that looks like a “T.” Pond blocks extend the entire cap to the side of the pan rail and have a larger flat register alongside the main bearing bore. Pond also adds a dowel pin for positive cap location.
The Genesis iron block has siamesed cylinders; they join together rather than having water flow between them. This allows a bore diameter far larger than any factory FE. At Survival Motorsports, we’ve over bored 4.375 inches frequently, compared to the original equipment (OE) parts, which become marginal at anything beyond 4.270 to 4.280 inches. The Genesis and Pond aluminum blocks use pressed-in-place cylinder liners and are good to roughly 4.310-inch bore diameters. Any build targeting serious high horsepower would be well served by starting with an aftermarket block.
The Genesis block looks virtually identical to a factory 427 on the outside, with the same screw-in core plugs and casting contours. Even a sharp eye cannot tell this from an original. The Pond block looks very similar with minor changes—larger cooling passages make for a smoother exterior, and the use of CNC O-ring sealed plugs tell the knowledgeable observer that this is not a stock piece.
Written by Barry Robotnik and Republished with Permission of CarTech Inc