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 The intake port face of the...  The intake port face of the 5.7 head casting (bottom) differs from the 6.1 in its smaller, nearly square port openings. Notice the larger rectangular ports of the 6.1 head (top). The 6.1 port volumes are about 20-percent larger than those of the 5.7. Obviously, intake manifold gaskets don't interchange.  Identifying a 5.7 Hemi head...  Identifying a 5.7 Hemi head is a simple matter of looking for this raised hump at the top of each intake port. Unlike previous Hemi engine families, Gen III Hemi heads are not interchangeable from one side of the block to the other.  The exhaust port openings...  The exhaust port openings (and gaskets) are also different. The 5.7's square ports (bottom) are generous and conjure images of the mighty 426 Hemi, while the ovoid shape of the 6.1 (top) is similar to the '71 D-4 Pro Stock head. Like the intake ports, we're looking at an approximate 20-percent difference in port volume between the heads. The 5.7 head carries casting number 53021616 BA; the 6.1 bears casting number 05037369AA.  The 6.1 (top) has slightly...  The 6.1 (top) has slightly larger combustion chamber volumes and is fitted with larger 2.08/1.600-inch I/E valves. The 5.7 (bottom) has 2.00 / 1.550-inch I/E valves. As mentioned, swapping 6.1 valves into the 5.7 head delivers a 7-percent flow improvement.  Topside, there is little difference...  Topside, there is little difference between the 5.7 (bottom) and 6.1 head castings. Both share the same bolt spacing, valve angle geometry, integrally cast spark plug wells, and external threaded accessory attachment positions. Overall weight is also nearly equal. Both are excellent pieces.
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