{"content":[{"text":"American Motors' first straight-six engine was the It was produced from through in both \n overhead valve OHV and flathead L-head side-valve versions. Sometimes referred to as the \n engine, this engine was originally designed by Nash and introduced in the Nash Ambassador \n model. It featured only four main bearings , unlike the 7-main-bearing flathead engine it \n replaced. It was a flathead design displacing It was redesigned as an OHV engine in The \n flathead version was discontinued for â€”, but reemerged in as the economy engine for the \n \"new\" Rambler American. When the engine was changed to an OHV configuration the water \n pump was moved from the left side of the engine driven by a shaft extending from the back of \n the generator to the front above the timing chain. When the flathead model was reintroduced it \n also received the new water pump. Equipped with such high quality parts as forged crankshafts \n and connecting rods , these engines earned a reputation for remarkable durability. The flathead, \n however, was prone to the typical flathead problem of overheating under sustained heavy load. \n This was from the hot exhaust traveling through the cylinder block to the exhaust manifold. \n American Motors introduced a die-cast aluminum block version of the OHV It was produced \n through The cylinder heads for the two types of block aluminum and cast iron are of similar \n design, but are not interchangeable. The OHV requires more periodic maintenance than \n newer-model engines. The head bolts must be re-torqued retightening process regularly. The \n cause of the headbolts loosening over time is believed to be thermal expansion and contraction \n of the head due to the rather heavy design. The head expands and contracts by as much as 0. \n The cast-iron liners in the aluminum block version can also shift if the head bolts are not \n properly torqued and the engine is allowed to overheat. Good replacement heads and aluminum \n blocks for these engines are now difficult to find. The company designed an entirely new \n six-cylinder with a short stroke and seven main bearing crankshaft for This design was \n produced in various forms through To commemorate the engine's May introduction, 2, \n \"Typhoon\" cars were made on the Rambler Classic hardtop body. All other AMC options except \n engine options were available. The new engine replaced the Nash Road tests by Consumer \n Reports described the new powerplant as \"a very smooth and quiet engine, which should give \n good performance. Increasingly stringent emission control regulations continued to decrease \n the engine's power output, making the smaller version inadequate as increasingly stringent \n safety regulations also made vehicles heavier. The was the base six-cylinder engine on many \n models through , and even towards the end of its usage was considered reasonably modern in \n design. After its midyear introduction in the \"Typhoon\" two-door hardtop as part of the \n mid-sized Rambler Classic line, the engine was adapted to fit into the smaller Rambler American \n by using a special short water pump, an adaptive piece also used in the â€” Jeep CJ Starting in , \n AMC raised the deck height to produce the , and the adopted the 's longer connecting rods and \n shared deck height with the Bore and stroke remained the same. In , the bell housing bolt \n pattern changed to match the larger version used on the V8 engines. Changes for the model \n year included fuel economy improvements that also reduced emissions and reduced warmup \n time. This was similar to a in stroke with a larger 3. Output for Rambler American Rally model \n gross :. This engine is considered reliable, inexpensive, and torquey. For , as part of a weight \n reduction program aluminum intake manifold, plastic rocker arm cover , the crankshaft was \n changed from a twelve counterweight design to four, saving approximately 20 pounds 9. This \n was similar to a in stroke, cast with a larger 3. The â€” units were measured under the new net \n rating system. The which had a larger bore is considered the ancestor of the 4. The new engine, \n which was introduced in for the model year, was a further evolution of AMC's six. The 4. \n Chrysler engineers continued to refine the engine to reduce noise, vibration, and harshness. \n The last in the line of the AMC inline sixes, the 4. Described \"as reliable as a block of wood\" by \n Popular Mechanics and ranked first among \"the ten best car engines they stopped making in \n the past 20 years,\" the 4. When introduced, the block-mounted oil filter check valve was \n eliminated on the 4. The first 4. Unfortunately, there are few scan tools capable of interfacing \n with the system to pull diagnostics codes. RENIX systems also have no permanent memory for \n diagnostics codes thus making the diagnosis of intermittent problems more difficult. In , the 4. \n Chrysler also enlarged the throttle body and redesigned the intake and exhaust manifolds for \n more efficiency, and the fuel injectors were replaced with higher flow units. Camshaft timing \n was also changed. Badging on most Jeeps equipped with this engine read \"4. Small changes \n were made to the cylinder head for the model year. In , the engine block was redesigned for \n greater strength. The new block had more webbing and a stud girdle for added rigidity of the \n crankshaft main bearings. Engines installed in Grand Cherokees carried the \" PowerTech \" \n name that had been used intermittently in prior years and on other Chrysler truck and SUV \n engines. The name was subsequently passed on to 4. The cylinder head was again changed for \n the model year to a more emissions-friendly design. Early heads are prone to cracking, causing \n coolant to contaminate the oil, which can lead to catastrophic engine failure. The head cracks in","bbox":{"left":0.050964,"top":0.031288,"width":0.897921,"height":0.894159}}],"images_bbox":[],"images_bbox_not_text_overlap":[]}