Building a Stroked 302 Ford

Big Power in a Little Package

Dennis MooreMay 26, 2005
Photo 2/26   |   For an inside look at the Smeding 347 Extreme, click here.
The Chevy small-block is undoubtedly the king of racing and hot rodding, but there is little doubt that the Ford small-block beats everything else for a solid second ranking in performance engines. In the mid '60s, the Mustang debut was a success because the high-performance 289 competed on an even footing with the Chevy 283. As the muscle car era progressed, the small-block Ford 289 and 302 fell behind in performance to the larger 327 and 350 Chevrolets. The maximum horsepower of a production line Boss 302 was 290 hp, while there were numerous factory stock small-block Chevys that easily exceeded that number. When Ford eventually upped the displacement of the small-blocks to 351 in 1969, the performance still never exceeded 290 hp.
If the history of the small-block Ford stopped with the end of the first musclecar era, we wouldn't be writing this article. The most relevant history of the small-block Ford begins with the introduction of the redesigned Mustang in 1979. Ford fanatics might remember this as the beginning of the 5.0 Mustang era, and they know this really started the 302 Ford small-block on its way to becoming the popular engine it is today. The '79-and-later 5.0 Mustangs were fast and affordable cars, relatively easy to work on, and responded well to engine modifications. Like the original '64 Mustangs, they helped start a new era of affordable factory performance cars. It seems as though history does tend to repeat itself. Just as the small displacement of the 289 and 302 was easily surpassed by the 327 and 350 small-block Chevys in the '60s, so has the small displacement of the 302 been surpassed in the modern performance era. Again, we are seeing small-block Chevrolets with larger engine displacements dominating the high-performance street scene.
Often referred to as the Windsor, after the city where the engines are manufactured, the 302 and 351 are the most common, with the 351 being the largest in the series. While the 351W has the displacement needed to compete with the 350 Chevy, it has certain drawbacks that make it less than ideal for installation into a 5.0 Mustang body, classic Ford truck, or early hot rod. One of the biggest advantages of the 302 Ford is the small outside dimensions. The 302 is 3 inches shorter and 2 inches narrower than the 351W, allowing it to fit into small engine compartments.
To retain the compact 302 dimensions and increase the engine displacement, many aftermarket companies have introduced crankshaft, rod, and piston combinations that will fit within the stock 302 block and increase the engine size to 347 cubic inches. They are called stroker kits. The kit consists of a crankshaft with a 3.4-inch stroke (the stock 302 crankshaft has a 3-inch stroke), eight connecting rods that measure 5.4 inches long (the stock connecting rods measure 5 inches long), eight pistons that measure 4.03 inches in diameter with 1.09 inches of compression height (the stock pistons measure 4 inches in diameter with 1.608 inches of compression height), and a set of 0.03-inch oversize rings. Installing the stroker kit into an engine block basically consists of an engine block rebuild. This requires that the cylinders be bored and honed, and the bearings, rings, gaskets, and seals be replaced.
Truckin' decided that we would find an engine shop in California that was familiar with installing a stroker kit into a 302 to demonstrate the procedure. We ran across a group of experts at Smeding Performance in Rancho Cordova, California, who specialize in building small-block Ford and small-block Chevy stroker engines. Ben Smeding and his group of machinists and salesmen are about the most dedicated group around when it comes to quality work. Over a period of a few days, these guys walked us through a 347 Ford buildup that was very impressive.
First, the Smeding Performance small-block 347 Ford is a new engine with all new components. The engine block is brand-new, straight from the Ford Motor Company, along with the stroker kit and new Edelbrock aluminum heads. Nothing is rebuilt or reused; the engines even come with a new timing chain cover and a new oil pan.
The engine is called the Ford 347 Extreme and sells for $4,895 out the door. It cranks out 380 hp at a low 4,600 rpm. The engine's relatively mild hydraulic roller camshaft really pumps up the low-end torque, while still producing excellent horsepower and giving the engine an impressive sounding idle. Starting with the small and lightweight size of the 302 Ford and adding the aluminum Edelbrock heads and aluminum intake manifold, a person would be hard-pressed to find a more compact street engine with a better power-to-weight ratio than the 347.
Before we get into the specifics of this powerful engine, some of the disadvantages of the stock 302 Ford need to be pointed out to compare them with the upgrades found on the Smeding Performance Extreme Ford.
The Stock 302 Ford
Other than the lack of engine displacement, the biggest drawback to the 302 Ford is the size and strength of the connecting rod bolts and nuts. The most critical point of strength on the connecting rod is the bolt and nut holding it together. No expense is spared in the quality of the bolt and nut on the connecting rod of a high-performance racing engine. All modern American-made V-8 engines will have a connecting rod bolt and nut that measure at least a 3/8-inch diameter. Some big-block engines will have a larger 7/16-inch diameter bolt and nut, with the Boss 429 Ford having connecting rod bolts that measure a full 1/2 inch in diameter. The 302 Ford has small 5/16-inch diameter connecting rod bolts and nuts. While there are many highly modified 302 Fords running around out there with the stock connecting rods, the truth of the matter is they are living on borrowed time.
The size of the intake and exhaust ports in the stock 302 head are very small. Port size is measured in liquid volume. The intake port of the stock 302 cylinder head holds 145 cc of liquid. To equal the port flow of a stock Chevy small-block intake port, the Ford's intake port volume needs to be increased to at least 160 cc. The exhaust ports in the Ford head have a hump that restricts exhaust flow. Called the thermactor port, it is designed to work in conjunction with emission controls to introduce air into the exhaust. Most American-made V-8 engines introduce air into the exhaust manifold and do not have a restricted exhaust port like the Ford. The stock valve diameters of a 302 Ford are also very small.
The intake valve measures 1.78 inches and the exhaust valve measures 1.45 inches. The intake and exhaust valves of a stock 350 Chevy measure 1.94 and 1.5 inches in diameter. The 3/8-inch diameter rocker arm studs have been eliminated on the '78-and-later 302 Ford heads. The rocker arms are held in place with smaller 5/16-inch-diameter rocker arm bolts.
The '69-and-later small-block Ford engines will not have adjustable valvetrains. Valve lash adjustments are accomplished by installing different length pushrods. Most American-made V-8 engines have the intake ports paired together at the ends of the cylinder heads. By pairing the intake ports together, an excellent intake manifold can be designed with equal-length passages and gently sweeping turns between the carburetor and the intake ports. The intake ports are different on a Ford engine. They are spaced evenly across the cylinder head, with some intake ports located very close to the carburetor and some located far away.
Designing a compact intake manifold that incorporates equal length passages between the carburetor and intake ports requires some tight radiuses on the turns. To design a manifold for a Ford with equal length runners, gently radiused turns, and the same flow capacity as other more conventional V-8 engines requires an aftermarket intake manifold with a high-performance design. However, the drawback to a high-performance design is that it mounts the carburetor higher on the engine.
The Smeding 347 EXTREME
The biggest performance improvement between the 302 and the 347 is the increase of 45 cubic inches to the engine. This is accomplished by installing a longer stroke crankshaft (3.4 inches) and increasing the bore size (4.030 inches). A new nodular iron crankshaft made by Scat Enterprises in Redondo Beach, California, is fitted into the main bearings of the Ford block. Whenever the crankshaft stroke is increased, the crankshaft counterweights also need to be increased in size to balance the engine correctly. Because the counterweights are larger in diameter, the stock connecting rods are not long enough to provide sufficient clearance between the piston pin boss and the crankshaft counterweight when the piston moves to the bottom of the cylinder.
The stock connecting rods are replaced with longer, high-performance connecting rods that measure 5.4 inches, center to center. These high-performance connecting rods also have stronger 3/8-inch diameter bolts and nuts. The pistons on the 347 Extreme are forged aluminum. Because of the increased crankshaft stroke and longer connecting rod, the piston for the 347 needs to be much shorter than a stock piston. The distance from the top of the piston to the center of the piston pin is called the compression height. The compression height dimension for the 347 is 1.09 inches. The 347 comes with Edelbrock Performer 5.0/5.8L aluminum heads. Large 170cc intake ports and large exhaust ports allow the 347 to breathe as well as any small-block engine. The intake valve diameter measures 2.02 inches and the exhaust valve diameter measures 1.6 inches. Rocker arm studs measure 3/8 inch in diameter and accommodate an adjustable valvetrain.
Possibly the best performing intake manifold ever designed for the evenly spaced Ford intake ports is the Edelbrock RPM Air Gap 302, PN 7521. It sits atop the 347 Extreme and supplies large amounts of air/fuel mixture to each cylinder. The manifold has equal length and gently radiused passages, and the high-rise design only raises the carburetor mounting pad 1 inch higher than a stock 302 intake manifold.
The engine comes equipped with a hydraulic roller lifter camshaft using the stock Ford roller lifters. All '85-and-later 302 engine blocks come machined for a roller camshaft and lifters, but because of the short deck height of the 302, the roller lifters can only be installed or removed from the block without the head bolted into place. The Edelbrock heads have a groove machined into the deck that makes installation and removal of roller lifters possible without removing the heads. The aftermarket performance camshaft included with the 347 has 212/222 degrees of intake/exhaust duration at 0.050 lift and 0.489/0.510 inch of intake/exhaust valve lift. The intake and exhaust lobe centerlines have a separation angle of 112 camshaft degrees. Activating the valves are fully adjustable aluminum roller rocker arms. The rest of the engine consists of a new high-performance oil pump, timing chain and sprockets, a new balancer, all new fasteners, and Fel-Pro gaskets and seals.

Sources

Smeding Performance
Boerne, TX 78006
877-639-7637
www.smedingperformance.com
Scat Enterprises
310/370-5501
scatenterprises.com

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