351 Clevland Cylinder Head Specs
- The Ford 351 Cleveland powered Ford's racing cars and street machines for only four years, 1969 to 1974, before leaving the automotive world. During that time the engine established an ability to adapt to a number of situations, from NASCAR to the family station wagon. Part of the reason for this adaptability came for the cylinder heads mounted on top of the engine block.
The Cylinder Head
- Reciprocating engines can be divided into two parts. Everything from the tops of the pistons to the bottom of the oil pan is called the engine block. It contains the pistons (the cylinders inside of which the pistons go up and down), the crankshaft and various pieces of metal that open and close valves, pump oil, and run accessories like the starter motor, timing belt and alternator. The part above the top of the pistons is called the cylinder head and forms the upper part of the combustion chamber. It holds the valves, which let in the fuel/air mixture and let out the exhaust gases. It also has tunnels, called ports, from the carburetor to the combustion chamber and from the combustion chamber to the tailpipe. The size of the valves and the size of the intake and exhaust ports are important to the value of the cylinder head. Ford used the cylinder head, the size of the valves and the ports to control the output of the engine.
The Least Among Them
- Ford produced a very mild form of the Cleveland 351 for use in passenger cars with strict emission controls. It had a two-barrel carburetor, a low compression ratio and small valves. The cylinder head for this low-output engine had intake valves with a 2.04-inch diameter, exhaust vales measuring 1.67 inches, an intake port size of 2.02 inches by 1.65 inches and an exhaust port size of 1.84 inches by 1.38 inches.
The Middle Ground
- In 1972, Ford produced a 351 engine with a lower compression ratio, but with a four-barrel carburetor, that produced 275 horsepower with a very calm idle and comfortable feel. The engine went into Ford's high-end passenger cars. The intake and exhaust valves were 2.19 inches and 1.71 inches respectively, and the intake and exhaust ports measured, respectively, 2.50 inches by 1.75 inches and 2.00 inches by 1.74 inches. All four-barrel variations of the Cleveland 351 had the same valve and port dimensions.
The Big Bullies
- Ford developed the 351 Cleveland in 1969 as a high-performance engine. The engine was given elements of the 385 big-block engine and the Boss 302 racing engine. It had poly-angle combustion chambers with canted valves. The valves were given lots of room for ventilation by a radical cam. The 1971 "Boss 351" moved the engine to a higher output with advanced technology. It had a high compression ratio of 11.7-to-1, solid lifters and an aluminum intake manifold and produced 330 horsepower. The Society of American Engineering, the professional association responsible for automotive statistics, changed the method of determining horsepower in 1972 and comparisons became difficult. The "Boss 351" had a special intake manifold, a high-lift, long duration camshaft, special valve springs and dampers, a 750-cubic-feet-per-minute carburetor, a dual-point distributor and was rated at 266 horsepower.