Today’s Ford engines, including the amazing Coyote 5.0-liter V8, almost make an enthusiast forget the struggles of modifying a traditional small-block Ford. Not so long ago, stock V8 engines produced just 170-250 horsepower, and through power-adder use, racers tried to double or triple the output. Technology advancements have placed the ability to make big power in the hands of many, along with a strong aftermarket supplying parts with enhanced materials, and designed so power can be increased without the fear of parts failure.
Many of today’s Mustang and Ford fans cut their teeth modifying the 5.0-liter H.O. engine, which made its mark in the mid-1980s. Producing just 225 horsepower (suitable output for the era), the five-point-oh was the catalyst for many a performance build. But racers quickly realized the limit of a production block.
So, what’s the alternative? The solution is easy, as companies like Dart Machinery and World Products have developed aftermarket blocks with the racer and street enthusiast in mind. Not only are the aftermarket offerings more robust, they’re engineered for performance, not for assembly line production. They feature stronger iron alloy (or aluminum) material, better oiling, and provide much larger displacement potential when paired with the corresponding rotating assembly.
People often say horsepower comes from the cam, heads, and intake—and certainly, adequate breathing is important. But what good is an expensive, well-thought-out induction system if poor ring seal, blown head gaskets, or wiped out bearings occur because of deficiencies in the block design? In other words, a winning engine starts with a solid foundation, and that means having a high-quality engine block.
Stock Vs. Not Stock
The engine block is the most extreme-duty component in a vehicle. It must withstand the immense rotational force of the crankshaft spinning—the up and down forces of the pistons and the rings dragging the cylinder walls–while the deck must remain flat to seal the combustion chambers and contain the incredible pressure developed during the compression and combustion cycles. It also has to survive the heat generated by friction and combustion, and it must be constructed to contain passages for oiling and water jackets for coolant. And, harmonics created by the cam and valvetrain haven’t even been mentioned yet. The block needs to be stiff enough to handle all this stress, but soft enough to be machined. That’s a tall order from one single component. If the block fails it will be an expensive proposition, so selecting the correct product for the application is important.
With a race block you’ll see improved ring seal and even gain power in low-horsepower applications. – Jack McInnis, World Products
In the case of the small-block Ford Windsor (including 302 and 351W), that limit is about 300-500 horsepower depending on the block you’re using. Fordnatics recognize 1969-1970 Boss 302 blocks and most 351 blocks as being stronger than the 5.0 H.O. (1985-95), but they still don’t compare to a modern aftermarket block.
“In the old days, power level exceeded the capabilities of the material,” states Disk Maskin of Dart Machinery. “The goal is to achieve a tensile strength so the block doesn’t crack, and then we design it to maintain ring seal. When it comes to making power, ring seal is everything–period,” he exclaims.
There’s an endless list of classes and combinations being built by today’s enthusiasts and both Dart Machinery and World Products meet or exceed the challenge of building blocks for these difficult requirements, some of which can surpass 2,000 horsepower. Each manufacturer offers a full complement of Ford Windsor blocks, from the budget-minded to the most extreme. Dart’s line includes the SHP, Iron Eagle Sportsman, Iron Eagle, Cast Aluminum and Billet Aluminum. World offers its Man O’War series in a variety of configurations.
Ford fans are always seeking increased displacement, which means larger bores and longer stroke crankshafts. Years ago, a 331 or 347 was considered big cubes for an 8.2-deck block (408 was it for a 351W), but that’s small potatoes these days. Cylinder bores in the Dart and World blocks are capable of being finished from 4.000-inch to 4.200-inches. This can produce 360-plus cubic inches on the 8.2 and on the tall-deck Windsor upwards of 470 cubic inches is possible from a small-block.
Strength, Durability and Material
Factory Block Limitations
Despite goodies like a roller cam, efficient long-runner intake, factory tubular headers, and EFI, the 5.0-liter was based around a thin-wall cast block that’s prone to cracking. Push one too hard and there will eventually be cracks in the main webbing and the lifter galley, as shown in this extreme example. High-RPM use regularly past 6,500-7,000 rpm will also cause this in short order.
Failures develop because the material is thin and the block lacks features needed for increased cylinder pressure and RPM. The small two-bolt main caps are weak and tend to walk (a term used to describe movement) and that can eat bearings and create vibration and harmonics that leads to cracks. Furthermore, these blocks have trouble maintaining cylinder head sealing, especially in boosted applications due to the small head bolts and thin deck surface.
“We make the blocks as strong as we can and we don’t leave anything on the table,” Maskin says. “The blocks are primarily made of iron used in the diesel industry and we have better machining processes–we don’t use a transfer line. Essentially, we do fully custom machining on our blocks.”
Dart’s SHP (Special High Performance) block can be used with Ford hydraulic roller lifters and lifter retainer to make swapping from a factory block simpler, while the Iron Eagle series (including the billet aluminum variant) offers extreme duty capability.
World Products has a complete line of Man O’War blocks that have proven successful on the street and on the track. They’re known for their Man O’War racing blocks that recently went through a complete resurrection.
“We just completed a heavy-duty revamp of our blocks. We retooled and made significant changes, including an upgraded material rated to 50,000 psi,” says World’s Jack McInnis.
“Stock blocks are generally cheaper to produce and made from thinner material. Race blocks are subject to greater stress from increased compression and cylinder pressure, increased RPM, and greater heat and friction. You want to avoid including cracking and ‘creep,’ which is a form of material deformation over time. With a race block you’ll see improved ring seal and even gain power in low-horsepower applications,” McInnis says.
“We also thickened the main webbing area, the area that surrounds the main caps and secures the crankshaft,” McInnis continues. “Number one main area thickness is increased by .080-inch and two, three, and four are .030-inch thicker. We also went from half-inch main bolts to 7/16-inch ARP hardware [bolts or studs can be ordered].”
It’s an interesting change, to drop the fastener dimension rather than increasing it, but there’s solid thought behind the move.
“You generally don’t see fasteners fail–you see the web area in the block fail,” McInnis notes.
World claims by reducing the hardware size slightly, but using a stronger fastener, they can leave more material in the block to increase overall strength while retaining clamping ability and preventing cap walk. In addition, virtually all aftermarket blocks feature four-bolt main caps that can be nodular iron or billet steel.
Dart’s SHP and Iron Eagle Sportsman and Iron Eagle Ford blocks have the benefit of receiving some of the engineering advancements Maskin discovered while building Pro Stock engines years ago.
“Our blocks feature Siamese bores for added strength. We primarily use a material found in the diesel industry, And we use (and perform) custom machining on each block. We also have aluminum versions that provide good durability and save 100 pounds over the iron block. If done properly, an aluminum block can make as much power as an iron block,” says Maskin.
Pipeline of Oil
Proper oiling is a major concern of any engine builder or racer. Adequate lubrication for the rotating parts, the cylinder walls, and the valvetrain must exist. The oil bath also provides a cooling effect within the engine, as it absorbs heat created by friction. To work properly, the block must have provisions to feed the proper amount of oil to the cylinder walls, bearings and valvetrain—and for the oil to drain back to the pan.
Racing engines have different oiling requirements than production engines. There are many ways to modify the oil system for improved performance, such as increased or decreased oil pressure and also modifying the oil volume flowing through the block. Driving the oil pump requires power and causes drag on the engine, so the racer must take care to spin the pump relative to the application’s requirements. How oiling system modifications are done ultimately depends on class rules, the type of racing, budget, bearing clearances, and the type of oil used. Each of these factors is interdependent with the others and must be carefully considered before modifications are made.
The typical racer uses a wet sump system with an internal oil pump. In the Ford small-block, the oil pump sits in the front of the block so oil travels from the pickup in the pan, into the pump, through the filter, and into the block. In a production block, oil is first directed to the cam and then to the crankshaft. Both Dart and World change the oil circuitry to send the oil to the mains first.
“Our blocks are setup with priority oiling to the main bearings,” McInnis says. “We also enlarged the oil passages in the main galley and the supply from the filter pad. That’s where the restrictions are.”
Seal It Up
When it comes to making power, ring seal is everything. Period! – Dick Maskin, Dart Machinery
The improvements found in all of these blocks also provide more stability in the deck area. When the cylinder head is stabilized, the racer is less likely to find loose intake manifold bolts during maintenance between rounds. The strong cylinder walls mean the cylinders remain round and true; this is a critical area for power, as an out-of-round cylinder can rob a ton of power as ring seal fluctuates. Increased thickness is also found in the oil pan rails, providing stability to keep the oil pan gasket sealed.
Adding more cubic inches to an engine offers an easy route to increased power–this extra displacement comes by increasing the bore size, the stroke, or both. Boring a cylinder increases the diameter of each bore, and requires careful machining of the cylinder bores. A longer stroke requires a crankshaft with the connecting rod throws moved further from the crank centerline and a properly sized connecting rod and piston. This is advantageous as long as the piston can remain stable. Increasing the stroke on 8.200-inch deck height factory blocks will cause the piston skirt to come out of the bore at BDC. Aftermarket blocks have longer bores that extend deeper into the crankcase.
Stroking an engine has a greater effect of increasing displacement, but both are important to performance. When it comes to the small-block Ford engine, having the ability to stuff more displacement in the stock architecture is also helpful as this allows racers to retain many parts they already own, such as the oil pan, distributor, intake manifold, and headers.
Dart and World offer a wide range of aftermarket Ford blocks with varying deck heights so the enthusiast can select between a multitude of bore and stroke combinations. Most common are the 8.200-inch (302-based) and 9.500-inch (351-based) deck height blocks, but there are also 8.700-inch and 9.200-inch deck height blocks available.
A major part of the displacement equation comes from the crankshaft, and that’s where things get funky with the small-block Ford. There are many options for stroke and main journal diameter. Factory 302 engines use a small 2.248-inch journal size, where the production 351W uses a huge 3.000-inch journal.
The larger main journal adds strength to the crankshaft, but it also adds weight and increased bearing speed, which is not so good. The larger size means there’s more area, more RPM, and more friction. The compromise is the 351 Cleveland journal size, which is 2.749-inches; ready-to-go aftermarket cranks are available in a variety of stroke lengths with either main journal size.
Production 302 and 351 engines use the same 4.000-inch bore dimension–far smaller than the 4.185-inch (Dart) and 4.200-inch (World) maximum bore dimensions. It’s important to note that the safe overbore limit on most factory Ford blocks is .030-inch. Stock engines can be taken past .030-inch overbore in some instances, but it’s not typically recommended on a stock, thin-wall casting, as cylinder wall strength is compromised.
A Bevy Of Choices For Ford Owners
So, how big can a small-block Ford go? With a 4.200-inch bore and 4.000-inch stroke, one can be taken to 470 cubic inches. Of course, finding maximum power with larger displacements requires sufficient camshaft and induction, or copious levels of boost.
The small-block Ford engine has proven itself in many race classes over the years, from NASCAR to NHRA, to the trendsetters running the platform in NMRA and NMCA heads-up drag racing competition. These racers are using blocks like these from Dart and World to achieve incredible performances. There are many specifications and dimensions when it comes to aftermarket Ford small-blocks, and Dart Machinery and World Products have gone to great lengths to supply Ford enthusiasts with a variety of blocks to fit their requirements needs, whether it’s for a mild rebuild or an all-out race engine.