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340, larger than stock cam (no specs), RPM Air gap, stock bottom end, headers
Looking for a Holley 750 double pumper
I think I have it narrowed down to the 4150 Street HP,
anyone run this carb on a mostly street driven car??
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I had an 850 on a mild 450 hp 360 which ran hi-11`s at L.A.C.R. and bigger than "Suggested" cam in the same motor. Now that I`m finally getting a handle on these things a 750 in NOT too big and I can and have recently dialed a couple in that are working great including a 750 Speed Demon on a 4-speed truck that went from 13.30`s to 13.10`s and went from 15 mpg`s to 17............MILD smallblock Ferd.........

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But this mechanical 6 pack setup replaced the 4bbl and single plane. The engine seems slightly stronger with the 6 pack even with the 1,150cfms and no jetting!

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~813 cfm in 4 bbl terms.

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No .. this is the mechanical setup sold in the late 70's early 80 through DC. The end carbs are a 850dp cut in half with slabbed throttle shafts and all. The middle is a 355cfm which I removed the choke plate and shaft.

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Right but if you look at it this way. A motor will only draw in so much cfm of the carburetor. It doesn't matter what carb, style, or model if motor only can take in 500 cfm and you use a 650 then what? Is it to big now? You can run any carb you want but if it's a street set up then who gives a turkey about size really lol. As long as motor is getting fuel and is working like it's supposed to.

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I'd love to own the competition series TQ (1000 cfm), but those are like hen's teeth

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Not that again! Two-barrel carbs are rated differently, you need to divide the two barrel rating by the square root of two (1.4142) to convert to a four barrel reading. For 1350 two barrel cfm that equates to 955 four barrel cfm. BUT, the carb setup opened the end carbs only as much as the engine needed so I don't think any stock 340 ever used all of the 6-pack capacity.

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And Dog Days says this--->

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Not that again! Two-barrel carbs are rated differently, you need to divide the two barrel rating by the square root of two (1.4142) to convert to a four barrel reading. For 1350 two barrel cfm that equates to 955 four barrel cfm. BUT, the carb setup opened the end carbs only as much as the engine needed so I don't think any stock 340 ever used all of the 6-pack capacity.

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Not to start in and make a mess of things, but what is the conversion for the stock 6pack equal to in 4bbl. terms/cfm??

And the mechanical MP unit cfm rating in 4 bbl. terms?

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340, larger than stock cam (no specs), RPM Air gap, stock bottom end, headers
Looking for a Holley 750 double pumper
I think I have it narrowed down to the 4150 Street HP,
anyone run this carb on a mostly street driven car??
Opinions

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Opinions are all over the place, aren't they? One important piece of information that carb questions should include is the OP's desire and/or ability to properly tune the carb. And also, what's more important to you; maximum performance or maximum drive-ability?

Most guys are not carb tuners and don't have the wide band, drill bits, jets, bleeds or knowledge of the carb's circuits to get the most out of their choice of carb. For them, the carb that comes out of the box closest to the design and tune that their combination likes, is usually the best choice. Or at least the best starting point.

There are a lot of different configurations of 750 cfm carbs. All of them will run your car, but some will do a better job ON YOUR COMBO than others. But that doesn't necessarily mean one is actually better than the others, just maybe that it is closer to the tune that you combo likes.

A good tuner with the proper tools and experience can start with most any 750 and get it to rock. But the farther away from the combo's preferred tune the carb is, the more changes the tuner has to do to get it right. So whether an experienced tuner or not, it is best to start with the carb that is closest to the tune that your combo wants.

And irregardless of the tune, some carb configurations are designed to do one job better than another. Like spread bore or square bore, mech secondaries or vacuum, annular or down leg boosters and on and on.

Sorry for the long response. But carb selection is as complicated as cam selection. Most guys turn to a cam grinder for recommendations. And any cam guy worthy of your money will want A LOT of info on the engine, drive train and the customer's desires before he makes a recommendation.

In order to get the optimum carb, the same approach should be taken. How about asking Thumper to set one up for you? Tell him what you want and what your combo is and let him pick the platform and through his tune in it. That would likely get you a better carb than the one ordered by a catalog number.

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Holley 650 ultra double pumper...best carb OOTB for your application.

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Absolutely NOT the best choice for the OP's mostly street driven car with an automatic and 3.23s. Unless he enjoys a tuning challenge. Every circuit would need a good amount of tuning to keep it from loading up the combustion chambers, washing down the cyl walls, diluting the oil, and wasting a lot of fuel.

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Holley 650 ultra double pumper...best carb OOTB for your application.

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Absolutely NOT the best choice for the OP's mostly street driven car with an automatic and 3.23s. Unless he enjoys a tuning challenge. Every circuit would need a good amount of tuning to keep it from loading up the combustion chambers, washing down the cyl walls, diluting the oil, and wasting a lot of fuel.

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Yep.........the BEST one is a modified one because of the different tunes each carb series has and even though close, not perfect...........kinda like guys buy Afco shocks then send em in to be "Fine tuned" to suit YOUR needs. You want to talk best "Bang for the buck"? Get a 750 MODERN carb not some wore out one that needs EVERYTHING anyhow, and have it worked cos trust me, EVERY carb needs something and as we speak I re-did two "Modified" carbs by two well known shops and although close each had issues..........the same ones I see in every carb. Too rich here, stumbles when I do this goes lean here. You get the picture............