The right action is leaving a gap of .030“ - .060” (1/32“-1/16”) between the head and manifold at the skinny lip. This gap needs to be even all around on both heads at the same time. It's in this little gap that the O-ring seals when the clamp squeezes it. When setting the heads & jugs for alignment and installing the manifold & O-rings with no clamps in place, the inside of the manifold should match the inside of the intake port all by itself with no forcing. Don't worry if the gap seems too big. It will shrink when the heads & jugs get tightened. The last test is when clamps get tightened, that the alignment is still on. Before you tighten the clamps, you will note that the O-rings are proud of spigot diameters. When the clamps squeeze the O-rings to the spigot dia., the seal to gap occurs. During the tightening, you may have to tap the manifold back into alignment until the clamps grab onto the spigots.
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