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195.6 AMC's first straight-6 was the 195.6 in³ (3.2 L). It was produced from 1958 through 1965 in both OHV and "flathead" side-valve versions. Sometimes referred to as the "196" engine, this engine was originally designed by Nash in the 1930s as a Flathead , and redesigned as an Overhead Valve (OHV) engine in 1956. The flathead version was discontinued for 1956 and 1957, but reemerged in 1958 as the economy engine for the "new" Rambler American. When the engine was changed to an OHV configuration the water pump was moved from the left side of the engine (driven by a shaft extending from the back of the generator) to the front above the timing chain. When the flathead model was reintroduced it to received the new water pump. Equipped with such high quality parts as Forge d Crankshaft s and Connecting Rod s, these engines earned a reputation for remarkable durability. The flathead, however, was prone to the typical flathead problem of overheating under sustained heavy load, from the hot exhaust traveling through the Cylinder Block to the Exhaust Manifold . AMC introduced an aluminum block version of the OHV 195.6 in³ (3.2 L) engine in 1961 . It was produced through 1964 . This engine used cast iron cylinder liners and a cast iron head. The Modern Era I-6 The company designed an entirely new six cylinder for 1964 , and this version is still in production. First produced in 1964 and introduced as an option in the Classic and Ambassador in the middle of the 1964 model year, the 232 in³ (3.8 L) "Typhoon" inline-6 was AMC's first modern 6-cylinder engine. It replaced the Nash 196 in³ (3.2 L) OHV I-6 in the Classic and Ambassador in 1965 (the first use of a six in the Ambassador since 1956). In 1966 a 199 in³ (3.3 L) version finally replaced the aging 196 in³ (3.2 L) OHV and L-head engines. To commemorate the engine's May 1964 introduction, 2,520 "Typhoon" cars were made on the Classic hardtop body. Each featured the new 232 six, Solar Yellow body paint, a Classic Black roof, and a distinctive "Typhoon" script in place of the usual "Classic" name. All other AMC options (except engine options) were available. Both the 199 and 232 featured a 3.75 in (95 mm) bore, and either a 3.0 in (76.2 mm) or 3.5 in (88.9 mm) stroke. The 199 was discontinued in 1970; the 232 was offered alongside the 258 (made by using a 3.9 in (99 mm) stroke crankshaft in the existing block) during the 1970s, but was discontinued in 1978. Increasing emissions controls continued to rob the engine of power, making the smaller version inadequate as safety regulations also added weight to the vehicles it was required to push around. 199 The 199 in³ (3.3 L) 199 was produced from 1964 through 1970 . Applications: 232 The 232 in³ (3.8 L) 232 was produced from 1965 through 1978 . Applications:
258 The 258 in³ (4.2 L) inline-6 was produced from 1971 until 1989 . It featured an Undersquare 3.75 in (95 mm) bore and 3.90 in (99 mm) stroke; it was otherwise identical to the 199 and 232. Later 258 models (starting with the 1980 model year for California AMCs, 1981 for California Jeeps and 1982 for all other applications) are equipped with AMC's CEC system. Applications:
2.5 ]] The 2.5 L inline-4 was a version of the 258 bored to 3.88 in (99 mm) and de-stroked to 3.19 in (81 mm). It appeared in 1984 and was produced through 2002 for the Jeep Wrangler . Output that final year was 120 hp (89 kW) at 5400 RPM and 145 ft·lbff (197 N·m) at 3250 RPM. This engine was used in the following vehicles:
4.0 The 4.0 L (3956 cc) Straight-6 was an evolution of the 258 and 2.5 and appeared in 1987 . It had the same 3.88 (98.4 mm) bore as the 2.5 with a longer 3.41 in (86.7 mm) stroke. Although it was called the Power Tech Six since its 1987 inception, that name is more connected with the replacement for this engine, the 3.7 L PowerTech V6 . The 4.0 will be discontinued at the end of the 2006 model year as the Jeep Wrangler will instead get Chrysler's 3.8 L OHV V6 . The first 4.0 engines in 1987 had RENIX ( Renault + Bendix ) engine control systems, which were quite advanced for their time, but are now handicapped because there are very few scan tools which can be "plugged in" to a RENIX system for diagnosis. The Renix also used a very advanced Knock Sensor which allowed the computer to know if detonation was occurring, thus allowing the computer to make the appropriate changes to prevent this. The 1987 RENIX 4.0 made 173 hp (129 kW) and 220 ft·lbf (298 N·m) of torque. In 1988 the 4.0 received higher flowing fuel injectors, taking output to 177 hp (132 kW) and 224 ft·lbf (304 N·m) respectivly. In 1991, Chrysler Corporation, the new owners of the Jeep franchise, redesigned the RENIX engine control computer and changed the intake port design for more power. Thus the 4.0 H.O. (High Output) was born. Chrysler enlarged the throttle body and redesigned the cylinder head for higher flow. The intake and exhaust manifolds were also changed for more efficiency, and the fuel injectors were once again replaced with higher flowing units. The camshaft was also changed to a higher lift one. The net result of all these changes was an engine that made 190 hp (142 kW) and 225 ft·lbf (305 N·m) of torque. The 4.0 was kept the same until the 1995 model year when small changes were made to the cylinder head. In 1996, the engine block was redesigned, and a new strengthend unit was then used. The new block made use of more webbing cast into the block, and a stud girdle for added rigidity of the crankshaft main bearings. The cylinder head was also again changed around 1998 to a lower flowing, but more emissions friendly, design. The 4.0 engine is slated to be in production in North American until 2006, when the Jeep Wrangler TJ is replaced by the new JK design which uses Chrysler's OHV 3.8 L V6. It is foreseeable that this engine may be made for many more years in China, which still produces a slightly modified version of the XJ Jeep Cherokees with 2.5 and 4.0 engines. Output in 2004 is 190 hp (142 kW) at 4600 rpm with 230 ft·lbf (312 N·m) of torque at 3000 rpm. It has a cast iron engine block and cast iron OHV cylinder heads. It uses SFI Fuel Injection , has roller rockers, and features cast iron connecting rods, a one-piece cast camshaft, and a cast aluminum intake manifold. This engine is considered one of the best offroad engines ever made. The extreme low end torque is ideal for trailing and rock crawling. The only downfall to the engine is the low power output for mudding applications but this can be fixed with various aftermarket options including a supercharger for the engine. Interchangeability within the late AMC/Jeep engine family is superb. The better flowing 4.0 L heads can easily be modified to fit earlier engines right along with the fuel injection system. The longer stroke 258 crankshaft and rods will drop right in the slightly larger bore 4.0 L block, easily creating an even higher torque 4.5 L engine with the stock bore (4.6 L bored 0.030" over, and 4.7 L with a 0.060" overbore). Blocks should be sonic checked for adequate cylinder wall thickness before boring 0.060" over. This engine was used in the following vehicles::
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