[What'saCobra?]

OK. A few more opinions.

Power valves.
Unless the induction system is very restrictive and keeps the valve closed (and lean) because the vacuum is above the power valve rating at WOT, i would not remove it on the street. The better choice would be to replace it with a higher rated valve, so it will still open. Unnecessarily lean high end operation on the street is big risk for no benefit.

The new power valves are blow-out proof (if you backfire through the manifold, for instance, at a momentarily too lean a mixture, perhaps during the start sequence) enough to be very functional today. There is no damage of much risk on the street of consequence with the power valve blown unless you are dragging. And we said they are now almost completely blow-out proof.

Under race conditions, where you have many thousands of dollars budgeted to each race and you cannot take any random risks, i would prefer to have the carb re-worked to operate at all points on the curve without the power valve and its associated circuitry.

To do this, among other things, you will have to increase jet sizes perhaps between 5 to 10 sizes to operate correctly at WOT and you will have to pick that rpm region you are most concerned about and tune for it. The trade-off is that the mixture will be too rich at part throttle; which is why the fuel burns off at the pipe ends when you let off a little. Well, unless you contaminate the plugs, a real problem on some engines/plug combinations, the excess fuel is not really that bad, because it only happens for a few seconds.

Some racers, though, still use the power valve and have learned to manage the risk with careful inspection and maintenance. But, race engines are much more prone to intake backfire anyway, so i don't like the risk. But, that said, i have used it.

All this means is use the power valve on the street, for sure. It is there for good reason and it works very well indeed when set up correctly. Then you can lean for top end power much more safely.

Annular Boosters
Great idea. Mostly for tuning a race car. We know that the venturi booster signal characteristics, circuit diameters and seat needle capacities are related to each other. And we know that (for gasoline, unblown, unnoxed) these are usually large enough for street use, balancing power and economy, because the manufacturer has tested the carb both on the bench and on the street. Extensively. i am not too certain that i could make a better balance than Holley. But, some engines, do respond to changes better. In my view, the only way to be sure is to dyno tune, with lots of take-offs of the carb, and revision schedules. Big job to do right, not for me.

On the other hand, perhaps some engines of very large displacement need larger signals and passages to deliver enough fuel. An annular booster with a higher rating might help. At the least, use an EGT on one of the leanest pipes (usually an extreme rear and hot corner of the engine) and observe the temps. High temps at high rpm will let us know if there isn't enough fuel pretty quickly.

And, although the boosters have been around since the early eighties, the new HP sensitity to proper fuel requirements at low airmass flows, makes the boosters less necessary. i did use them on a few set-ups before the HP series, where i had to use the 4150/4180's for historical (hysterical) reasons. It did help correct the early carbs poor response rather nicely. Remember to reduce the main jet sizes correspondingly, perhaps 3 to 6 sizes. Note that these are race carbs.

i also like the velocity stacks, but the new smoothed lip of the HP series reduces the need for them. (See my last picture.)

But, these are the rantings of an amateur and your results may vary. The most common carb errors i see are mickey-mouse air filters that are too small, 2" or 21/2" exhaust pipe ID's, too much carb and old designs that never were any good from the git-go.

Once upon a time i worked with a famous Moresville engine group for a short while. It was quite obvious to me that they maximized the horsepower area under the entire power curve at WOT on the dyno to compare changes between designs and set-ups. Even they depended on carb specialists to rent them induction systems. And the Morresville guys only rented their engines to the teams for several million dollars a season. No purchases were available. Only contracted rents. So, if even THEY rented carbs, my knowledge about carbs is only useful to myself and the one or two of my own projects i have to get right, not NASCAR competition.

Trust me, carburation is a black art at extreme performance. Many secrets i wish i knew.

But, you likely knew all that.