The engine block is the foundation on which everything is built. What you’ve got to work with determines the best-possible choices for you down the road in your engine build. The information that follows will allow you to properly identify the wide range of factory blocks that were made, and the distinctive characteristics of each.
Block identification is straightforward with 221, 260, 289, and 302 cubic-inch Fords. The 221 and 260 are both five-bolt bellhousing blocks with either a 3.500- inch bore for the 221 or 3.800-inch for the 260. Casting numbers and date codes are C2OE and C3OE, located just above the starter. These blocks are easy to spot because their bores are smaller than the 4.000-inch bores found on the 289/302. Deck cooling passages are an odd triangular shape as well, which is another element that differentiates them from the 289 and 302. Early 1962 model year 221 and 260 blocks had two 11⁄2-inch freeze plugs on each side, which later became three freeze plugs in 1963. These early blocks are also differentiated via engine mount bolt hole spacing, with the earliest 221/260 blocks being 6 inches apart along with two freeze plugs instead of three. Changes to three freeze plugs and different engine-mount bolt hole spacing happened early in the 1963 model year to reduce NVH.
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The 289 block entered production in the 1963 model year with a five-bolt bellhousing bolt pattern just like the 221 and 260 along with improvements mentioned earlier. The 289 blocks have casting numbers of C3OE, C3AE, C4OE, C4AE, and C4DE. Beginning with the 1965 model year, Ford revised the 289 to a six-bolt bellhousing bolt pattern to reduce NVH. Casting numbers are C5AE and C6AE. The 289 High Performance V-8 had the same block as the 289 2V and 4V, with the exception of wider mainbearing caps. This rule applies to both five- and six-bolt bellhousing blocks.
The 302 block appeared for the first time late in the 1967 model year in both 289- and 302-ci applications that had a C8AE or C8OE casting number with a “302” in the valley area. What made the 302 block different than the 289 was longer cylinder skirts—.015-inch longer to accommodate the 302’s longer 3.000- inch stroke. The 302 block evolved to some degree in the years following 1968, with casting revisions worthy of note. While most of these blocks are interchangeable with 289 derivatives dating back to 1965, it is important to note the clutch equalizer shaft pivot boss on the left-hand side was eliminated from the 302 block beginning in 1975. This means you need a bolt-on clutch equalizer shaft pivot bracket for a 1975+ 302 block if you’re running a manual transmission and the classic Z-bar clutch linkage.
If you’re restoring a classic Mustang or other type of vintage Ford, your search for a corresponding numbers matching block is challenging because there aren’t as many salvageable cores as there used to be. For the purist, the block must have that correct casting number. For example, a 1965 Mustang should have a C4 or C5 casting number, depending upon vehicle build date. The casting and engine build date codes should fall within 30 to 60 days of the vehicle build date. One example might be “5A26” (January 26, 1965) or “4F17” (June 17, 1964), which means year, month, and day of casting or manufacture. One good example of a casting number might be C5AE-6015-E for a 289 block. Look for these numbers because they show you the way to correctness.
If you find a numbers matching block with cylinder bores that have been overbored to 4.030 inches or beyond, the block can be sleeved by a qualified machine shop and returned to service. The cost to sleeve a block is approximately $100 per cylinder. Expect cost to go higher with time. The good part about sleeving a used block is the seasoned iron from that steady cycling of heating and cooling over time. Cylinder sleeving is discouraged if you’re going racing because, no matter what anyone tells you, sleeves are not as stable as iron bores. NOS Ford service blocks from the 1960s are expensive and hard to come by, but still out there.
It is always a good idea to check any block you’re considering for cracks and severe warping before machine work is performed. This process can be accomplished by any qualified machine shop before expensive machine work begins. As a rule, small-block Fords rarely suffer from cracking unless there has been a bad overheat or extraordinary circumstances such as an accident or the block being dropped. Weak spots are generally around the decks near cylinder head bolt-holes and cylinder bores.
It is believed Mexican blocks have higher nickel content, which isn’t necessarily true. Respected Ford engine builder John Da Luz in San Diego, California, has weighed all Ford blocks and found a Mexican block weighs the same as a U.S. block. When you add nickel to an iron casting, you add weight. This debunks the higher-nickel-content theory, more or less. What makes the Mexican block better is its wider main bearing caps, as you see on the 289 High Performance block. Mexican blocks are an excellent source for wider main caps, when you can find them. If you install them on another block, line bore must be checked and honed as necessary to get the main saddles to proper size.
Ford’s limited-production 1969–70 Boss 302 engine block is highly sought after for its four-bolt main caps, heavier main webs, thicker decks, and screw-in block plugs. Because fewer and fewer cores are out there today, it isn’t racers going after these blocks, but restorers looking for authentic date-coded Boss blocks. Four basic Boss 302 block castings were produced: C8FE, C9ZE, D0ZE, and D1ZE-B. C8FE is the 1968 302 Tunnel- Port block, which was also used in early 1969 Boss 302 Mustangs and Cougars. Don’t be surprised to find a C8FE Tunnel- Port block in a 1969 Boss 302 production car. Most common are the C9ZE and D0ZE Boss 302 block castings. D1ZE-B is a Ford replacement service block.
Like the earlier 221, 260, 289, and 302 blocks, overbore for the Boss 302 block is limited to 4.040 inches, and I am even inclined to suggest no greater than 4.030 inches, especially if you intend to take it to 7,000 to 8,000 rpm. And like the rest, you can sleeve a Boss 302 block for about $100 per cylinder and go back to a standard bore.
Because the 351-ci Windsor block has a taller deck and additional webbing in front on top, identification is straightforward. The 351W has a 1.00-inch-taller deck in order to accommodate the 3.500- inch stroke. Based on a lot of experience, I’ve found 1969–1971 351W blocks appear to be stronger than subsequent blocks because of their higher nickel content. I admit I haven’t weighed these blocks side by side, which leaves this speculation open to debate. These early 351W blocks are typically numbered C9OE and D1AE. One other option is 351W blocks cast in Mexico for highperformance applications. They’re very hard to come by. I’ve seen them from time to time in North American-built Fords and Mercurys. Like the 302 blocks mentioned earlier, these blocks weren’t limited to Mexican-built vehicles.
Ford’s 351 Cleveland is one of the more limited mass-production V-8s the company has ever produced because it made them for only four years in North America (1970–1974). The 335-Series engine was produced in Australia significantly longer in 302- and 351-ci displacements.
Finding one of these blocks with a standard bore is challenging because so many of them have been rebuilt or recycled to scrap iron. Most have been bored to at least 4.030 inches. As with other small-block Fords already mentioned, 351 Clevelands can be sleeved and brought back to standard for about $100 a bore by a qualified machine shop. Through the years, I’ve found 351C blocks tend to crack more, which means you must have a block checked before expensive machine work begins.
Two basic 351C blocks (two-bolt and four-bolt main) were produced with a variety of casting numbers visible above the starter. This information enables you to identify these blocks without removing the oil pan.
Ford Australia produced a NASCAR Cleveland block for the North American market, but not much is known about this block. We do know these blocks had thicker cylinder walls and decks, along with four-bolt mains. The bad news is they were rejected and returned to Australia due to casting-core shift problems and sold on the Australian market.
Not all 351C engines produced in Australia had blocks cast in Australia. According to reliable sources, Ford’s Cleveland Foundry and the Michigan Casting Center produced 351C blocks for Ford Australia with North American casting numbers. Michigan Casting Center blocks received an “MCC” logo/code. Blocks produced both in and for Australia were used for both 302- and 351-ci engines. Ford Australia-produced Cleveland blocks are identifiable by their castin thermostat coolant flow restrictors instead of a brass insert like the North American 351C.
The 351M and 400M (“M” means Midland) are covered together because these engines employ the same raiseddeck Cleveland block. The M-block has a 1-inch-taller deck height (10.297 inches versus the 351C’s 9.206 inches) to accommodate the 400’s 4.00-inch stroke. This makes a 351/400M block easy to identify. However, the 351/400M block has a Ford big-block bellhousing bolt pattern, which means a big-block C6 or Top Loader for your M-Series engine build. This is the same bolt pattern used for the 385-series 429/460-ci big-blocks.
Because the 351/400M employs a raised deck, you must also think about accessory front dress issues such as power steering, air conditioning, and alternator. These items, when copped from a 351C, do not always interchange.
Ford Racing Blocks
Ford Racing Performance Parts (FRPP) offers us a great playing field when it comes to high-performance blocks for small-block Fords. Everything from a modest 5.0L street block to all-out racing is available. Here, I touch mostly on street hardware. The most significant block introduced by Ford Racing Performance Parts since this book was first published is the Boss 302 block (M-6010- BOSS302). It was a long time coming and basically a replacement for the 302 M-6010-A50 Sportsman block, which was in production for many years.
The M-6010-BOSS302 block is cast from the latest high-tech casting techniques at Ford’s Cleveland foundry, which has a long legacy of great engine castings including the 221/260/289/302 small-block and 351 Cleveland. Refining this technique came from years of practice developing durable NASCAR blocks that have a fierce reputation for reliability. What is different from the 1960s is computer aided design (CAD) used in casting modeling. When Ford adds virtual machining to the casting model, it’s time to calculate how much molten metal needs to be poured into the sand casting. Although this process saves Ford a bunch of money, it also means less metal. Cylinders are siamesed to make the block stronger. Although the new Ford Racing Boss 302 block has had some teething problems, it has panned out to be one of the best aftermarket blocks these folks have produced in a long time.
The Sportsman block was an excellent value and still is if you can find one new or used. The disappointing part was the halt in production of these A50 Sportsman blocks, which were such an excellent value for the money at around $1,000 each, new. And if you’re building a warmed-up street engine, the discontinued 1985–1999 5.0L production roller block was also a great disappointment because Ford gave you the option of starting with a new stock block instead of searching all over for a standard-bore used block.
I discuss the M-6010-A50 Sportsman block because there are plenty out there, new and used. At 135 pounds, the Sportsman block offers nodular iron architecture with wide two-bolt main caps. These blocks can be stroked to 347 ci. Ford Racing Performance Parts suggests no larger than 4.030 inches. The A50 Sportsman block is a great direct replacement for the common 1985–1999 5.0L roller block.
FRPP offers more race blocks than it does street blocks, and it makes your choice easier when you’re building a street machine or a weekend racer. The M-6010- BOSS302 is a great street/strip block, but a bit cost prohibitive if you’re on a tight budget. The A50 Sportsman block is more practical in terms of cost, yet it is no longer available from FRPP. Mission and budget determine which block you choose. Without any doubt, the A50 Sportsman is a more practical block for street and strip. You can throw 450 hp at this block without spending a fortune.
Useful Block Modifications
The seasoned Ford engine builder understands what it takes to make a great engine even better. This is why some of the best Ford engine builders around were consulted for this book. The most important improvements you want to make are cooling and lubrication. Oilingsystem improvements include chamfering oil passages and using restrictors where necessary to improve oil volumeand flow to important areas. You also need to think about coolant flow and where it’s needed most.
There has been a lot written and said about Ford Mexican blocks through the years. It has been said Mexican blocks have higher nickel content. But when experts weighed both U.S. and Mexican 289/302 blocks, they came up with the same weight, which debunks this long-held assumption. The main difference I’ve seen in Mexican blocks is wider Hi-Po-style main caps. When raw, Mexican blocks appear to have more nickel based on a shinier appearance. One of the quickest ways to identify a Mexican 289/302 block is by the humps at the front of the block, on each side below deck. These blocks are also identifiable by their Spanish markings and Ford-Mexico casting numbers.
Written by George Reid and Republished with Permission of CarTech Inc
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