AMC V-8s
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| − | AMC made some improvements in the Gen-2 design for 1970. This resulted in different block and head castings and slightly larger displacement. The only change to the block was adding approximately 1/16" to the deck height and increasing the stroke accordingly. The 290 became a 304, 343 a 360, and the 390 a 401 (with a little extra stroke in the crank than the 390). The 401 wasn't introduced until 1971. The 390 was kept for 1970 only by using a special piston -- the pin height was altered to keep displacement at 390 inches. The head casting was changed to create a slightly larger "dog leg" exhaust port (Gen-2 heads have rectangular exhaust ports) to improve exhaust flow. | + | AMC made some improvements in the Gen-2 design for 1970. This resulted in different block and head castings and slightly larger displacement. The only change to the block was adding approximately 1/16" to the deck height and increasing the stroke accordingly. |
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| + | Understanding is the GEN-1 to GEN-2 block deck height difference was 1/32" nominal, or 0.033", GEN-1 was 9.175" nominal block deck height and GEN-2 was 9.208" nominal block deck height per the Performance American Style booklet AMC printed in the early '70's, but have not measured actual AMC engine block castings to confirm these nominal dimensions stated in the Performance American Style booklet. | ||
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| + | The 290 became a 304, 343 a 360, and the 390 a 401 (with a little extra stroke in the crank than the 390). The 401 wasn't introduced until 1971. The 390 was kept for 1970 only by using a special piston -- the pin height was altered to keep displacement at 390 inches. The head casting was changed to create a slightly larger "dog leg" exhaust port (Gen-2 heads have rectangular exhaust ports) to improve exhaust flow. | ||
So there were four Gen-3 sizes: | So there were four Gen-3 sizes: | ||
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