Building a Stroked 302 Ford

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.