The instructions with my HEI from langdon said to try ported and un ported (direct from the manifold), one carb and two, to see which way works better.
The vaccum in the intake isn't actually constant-it varies with RPM and depends in part on the cam- a bigger cam produces less vacuum is the general rule. So, ported might not be enough.
'51 Chevy 1/2 ton w/'62 261, HEI, offy, fentons, dual carter/webbers, t-5 & 12 bolt posi
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