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...Perfect example-last night I'm reading a book about how to hotrod smallblock chryslers, and the author mentions something I hadn't paid attention to; the fact that an LA engine's valves open "on center" with the cylinder bore. Meaning, the valves aren't crammed toward the intake manifold OR the exhaust manifold side of the cylinder (as viewed from above). This shrouds them the least possible, which ford and chevy apparently do not. So, with a given bore size and valve size, an LA motor shrouds the valves less. The result-more flow UNDER ACTUAL OPERATING conditions. This is guaranteed to be missed by a flowbench, since they don't put a cylinder against the head in question...




Better rethink your theory: A cylinder head tested on a flow bench is mounted on a bore adapter that replicates the effect of being mounted on a block. That's why it's important to know the bore size of the adapter used (e.g. 4.00", 4.25", etc.) during any particular flow test to be able to account for any increased / decreased shrouding effect compared to the bore size the head is actually used with.