two overhead valves (OHV) per cylinder with pushrods and rocker arms. The cylinder head is a reverse flow design that puts the intake and exhaust ports on the same side of the head. For heat control, the exhaust was mounted on the firewall side of the engine, along with the intake. This left the spark plugs, distributor, fuel pump, oil filter and starter on the front side of the engine, for ease of servicing. The engine's name derives from it being the first "fastburn" engine offered by Ford. The definition of fastburn in the HSC is that 90% of the intake charge is burned within 15° of crankshaft rotation. To accomplish this, Ford put the spark plug in the center of the combustion chamber to minimize flame-propagation distance, and partially shrouded the intake valves, which accelerated and swirled the intake charge to more quickly fill the combustion chamber. These features were borrowed from Ford's programmed combustion (PROCO) engine research project. To reduce weight the intake manifold, water pump, and front cover are aluminum. A die-cast aluminum sump stiffens the entire engine assembly to reduce noise, vibration, and harshness (NVH). For its first year of production all HSCs used a carburetor. Later model year changes added a series of progressively more sophisticated fuel injection systems. All versions of the HSC engine, including the carbureted ones, are managed by Ford's EEC-IV engine control unit (ECU). This model controller added Keep Alive Memory (KAM), which enabled the engine to use adaptive control and self-diagnostics. From 1985 to 1992 the HSC engine was available in a "High Specific Output" (HSO) version producing and , compared to the regular 1985 version's and . To increase power Ford enlarged the ports, reshaped both the ports and combustion chambers, and unshrouded the valves. A camshaft with higher lift and longer duration was added. The intake manifold received larger runners and the air cleaner and exhaust system were redesigned to improve flow. The HSO engine is denoted by an "S" in the VIN. 2.3 L The 2.3 L HSC was introduced in 1984 in the Ford Tempo and Mercury Topaz. Bore and stroke are , for a total displacement of . This engine produced and of torque. For 1984 HSC engines for US 50 state cars were fitted with a 1-barrel Holley 6149 carburetor, while cars for Canada received a non-feedback Holley Model 1949. In 1985 American-market engines