Vacuum reading with dual plane was 1.4-1.5", with single plane 4150 was 1.1", and with single plane-dominator and tunnel ram .8-.9".
The only thing that I can think of to make more horsepower with this engine is.............
Well no doubt a forced-induction option could push the power up; but if I were determined to strive for that which can be achieved naturally-aspirated, and particularly when referencing the vacuum reading statement, then I would be looking at eliminating the carburetor(s) and switching to a fuel injection effort.
Notice that I didn't say 'electronic' fuel injection, as I don't think that the electrics would be required for your effort, or for the drag racing environment; and this also isn't a statement that mechanical fuel injection isn't possible for anything else either.
The problem (well yes, everything costs to much money
) is that there isn't a 'good' (for making power
) fuel injection manifold out there available; the old Hilborn and Argon examples just don't have the internal cross-sectional area necessary, so a manifold would need to be constructed. And this would prove difficult, this particularly due to the 'Y'-Blocks' "stacked" inlet port presentation layout.
But, since I have the Bridgeport, lathe, welding equipment, etc, and have dove into similar frustrating efforts before, I would probably begin by picking-up from somewhere a used larger throttle bore (e.g. Kinsler) I.R. manifold casting, something with spread ports might prove more flexible in the end, but perhaps just the more common S.B.C. stuff might prove cheaper to acquire, and start starring at it, for possibilities, cutting-up, welding, perhaps sectioning and grafting to one of the carb manifolds and shaping, attempting to establish if it could be made into something useful, or just as a pattern, if only to aid in the thought process for a next better effort. It would most likely prove to be somewhat unconventional, but..........
And if at first you don't succeed.................. ; and I know to well of this scenario! But then, who doesn't like a good challenge!
Scott.