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− | AMC 258 CID (4.2 Liter)
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− | Six-Cylinder: 258 CID (4.2 Liter) Engine Block Markings.
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− | Overhead valve gasoline engine.
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− | Cylinders are number 1 through 6 from front to rear (1 being the very front cylinder), in a firing order of 1-5-3-6-2-4.
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− | Crankshaft is on 7 main bearings and rotates in a clockwise direction, view from front of engine or vehicle.
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− | Camshaft is on 4 line bored bearings and is driven by the timing chain.
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− | Combustion is quench-type chamber (create turbulence and fast burning of air/fuel mixture for a good fuel economy).
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− | Build Date Code
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− | The engine Build Date Code is located on a machine surface on the right side of the cylinder block between the # 2 and # 3 cylinders.
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− | The numbers of the code identify the year, month and day that the engine was build.
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− | Explanation Engine Build Date Code
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− | Example: 3 10 C 11
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− | 1st Number Character is the build year: 3 = 1983, 4 = 1984
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− | 2nd and 3rd Number Characters is the build month: 01 = January, 12 = December
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− | 4th Letter Character code indicates the engine: C = 258 CID / 2v Carburetor / 9.2:1 Compression Ratio
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− | 5th and 6th Number Characters is the build day: 01, 02, 03 up to 31.
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− | The example code 3 10 C 11 translate to:
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− | 258 CID (4.2 Liter) engine with 2V Carburetor and a 9.2:1 Compression Ratio, built on October 11, 1983.
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− | Engines built for sale in Georgia and Tennessee have an additional, no repeating number, located on the right side of the engine below the build date code.
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− | Example:
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− | Kenosha-Build *E-1197277* or *W-1207177*
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− | Oversize or Undersize Components Markings
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− | Some engines where build with oversize or undersize components such as:
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− | Oversize cylinder bores.
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− | Undersize crankshaft main bearing journals.
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− | Undersize connecting rod journals.
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− | Oversize camshaft bearing bores.
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− | These engines are identified by a letter stamped on a boss between the ignition coil and the distributor.
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− | The letters are decoded as:
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− | B = All cylinder bores: -0.010-inch (0.254mm) oversize
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− | M = All crankshaft main bearing journals: -0.010-inch (0.254 mm) undersize
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− | P = All connecting rod bearing journals: -0.010-inch (0.254 mm) undersize
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− | C = All camshaft bearing bores: -0.010-inch (0.254 mm) oversize
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− | Example:
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− | Code letters PM mean that the crankshaft main bearing journals and connecting rod journals are 0.010-inch undersize.
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