This has been discussed at great lengths. Are you looking at cfm or brand or both? Quadrajets if done right can be an amazing carb, people love Edelbrock and Holley style too. It is a matter of tuning the carb to your specific engine. A 750 should be a good fit. I like the Holley style for me because I can tune it fairly easy.

 

Not really partial to brand, thought I would keep it original but am open to upgrading.

 

This is the place to contact for a quadrajet carburetor for your 396 cid. Call and talk to them about the right carb for your engine. Have all your engine specs when you call. Sean Murphy Induction: https://www.smicarburetor.com/ Here is an example of a quadrajet for big block Chevies 396-454. https://www.smicarburetor.com/products/sfID1/28/sfID2/9/sfID3/32/productID/837 Here is another example of a quadrajet built for 396-454 https://www.smicarburetor.com/products/sfID1/7/sfID2/9/productID/48 If you prefer a Holley they also have them too.

 

Does your manifold look like this?

If it does, a Q-jet is your carburetor.

 

If it does I'd think about a new intake to go with the new carb. An aluminum intake will perform better and knock off a bunch of weight.

 

Holley 650 (Double Pumper for Maunal trans or Vacuum for Auto) for your application would be a nice fit, I have a simular setup 396 (little more cam, producing about 450 horses) and have a 650 DP as I have a 4 speed, 650 cfm will be plenty for a street given car. Dont' fall into the huge cfm game, most street guys over carb way too much.

You can adjust yer jet sizes and squirters from stock to get it fined tuned.

 

As all have mentioned a carburetor works regardless of brand. Even the horrible Rochester 4GC carb was a fully functional carb but it got a bad performance rep due to the horrible intake manifold it was mated with.

Every carb made will flow the exact same amount of gas per cfm (If the carb didn't the motor wouldn't even run as it requires a very limited ratio of fuel to air). The difference in carburetor brand loyalty is based more upon the ease with which the user can tune the carburetor than any perceived performance potential. I have had to undo a lot of bad adjustments and even replace whole carbs that were not the correct size for the engine and application over the past decades in my performance oriented garage.

As an example the Holley 4165 is a spread bore carburetor that has all of the features of a 4160 carburetor, so it will respond to the same tuning efforts the same way. It doesn't make one horsepower more than a similarly sized Rochester QuadraJet carburetor which is probably the hardest of the popular brands to tune. This is because in addition to matching jets to metering rods you have to consider the step on the metering rod. Additionally many other features are made by choosing a different mounting hole and bending the actuating rod to adjust your change in that features operation. The advantage of a QuadraJet is that once it is properly tuned it stays that way for 100,000 miles. The Holley 4165 was made as a direct replacement for the Rochester QuadraJet, but the QuadraJet out lasted it; and there are fewer 4165's to be found on the street today.

Even Holley makes two levels of adjustability in their basic carburetors. There is the simpler, less adjustable 4160 that has a single feed and no secondary metering plate) and the much more adjustable 4150 series of square bore carbs. that you know as a dual feed. In the professional series of Holley 4150 carburetor there are more possible adjustments to make than many carburetor "experts" know what to do with (it doesn't stop them from trying though unfortunately).

The Carter AFB that was standard equipment on many High Performance Chevy engines when I was younger (350 horse 327 or a 409). They are now being sold today as an Edelbrock carburetor (Carter no longer makes a new AFB or an AVS). It is not as easily tuned, nor has it as many circuits as fully adjustable as a Holley Pro Series carb; but works just as well at metering gas to air (unless you have a ridiculous cam or live atop of a mile high mountain).

Because most Carter AFB models (Edelbrock carbs) are vacuum secondary carbs a long duration cam can cause issues. But then again a long duration cam will cause issues with almost any carb (due to reversion), and will actually pretty much require some degree of tuning it to something other than the out of the box condition.

As to size of your carburetor the factory used a 620 cfm Rochester Quadrajet on the 325 horse 396, a 650 cfm Holley 4160 carb on the 350 horse 396 and a 780 cfm Holley 4150 carb on the 375 horse 396. It was the cam that determined the 396 models RPM band (at least were it made power anyway; more so than as to how high it would spin if you just stood on it). So even though they were all the same size motor the cfm requirements increased with RPM bands increase.

However unless you desire to drive only on a circle track with your foot planted on the gas I suggest you consider a smaller ,instead of a larger carburetor (as determined by cfm). A carb that is too large for the street is no fun to drive.

Big Dave

 

There is a used Holley 4165 as an alternative:

http://www.ebay.com/itm/like/131704848420?ul_noapp=true&chn=ps&lpid=82

or you might want a new one:

http://www.jegs.com/i/Holley/510/0-...N=pla&catargetid=230006180003463514&cadevice=c&gclid=CP7twLv718oCFYEdHwodJG4H6A

Big Dave

 

Thanks for pointing me to some options. I am wondering if I should just go ahead and swap out the stock intake too.

 

What performance difference could I expect between buying and using a good SMI built qjet with the stock manifold or switching to say an Edelbrock manifold topped with a street avenger 770? Or would that be too much for my application?

 

A properly rebuilt Quadrajet that has been tuned to meet your engine's requirements makes all the difference in the world when compared to a corner store rebuild that is a mish mash of "good" parts from the many different cfm ratings and styles that were made over the years. Just because a part will fit inside the carb doesn't make it the correct part for the application. GM made seven different cfm rated carbs to fit a CHEVY (excluding the BOP carbs that had a different fuel inlet) and externally they all look alike. The springs to open the back barrels, the jets, rods, and boosters, as well as the venturi size all differ between the various models. You can not mix and match parts the way a woman sitting on a bench in Calacutta would do fitting a "rebuilt" carburetor together according to a picture on the wall before her.

The change in the manifold would be the biggest gain. First an aluminum manifold is lighter and every pound you drag around wastes gas and hurts your ET. Second point is the original manifold was designed for reduce cost in production man hours to roll the green sand on a bench and assemble a manifold from the component hand made parts. The newer manifolds were designed on a "Super Computer" (Edelbrock rented time on one just to simulate the wet fluid flow characteristics) which allows their new Edelbrock RPM Air Gap dual plane manifold to flow as well as the older Edelbrock Victor Junior single plane manifold; and still retain all of the advantages of a dual plane manifold. Edelbrock spent the R&D money and cast their parts using lost wax technology here in the US. That didn't stop the Chinese who have since copied them: as have most of the industry to one degree of success or another.

As to the carburetor size and brand, once again smaller is better for the street. Consider how much time you are going to spend driving o the street compared to track time. You change tires to race why not a carb? As to brand I use a Holley, I have been using them since 1963 when I got tired of multiple carbs on top of my 409. Carter didn't make one carb big enough back then, but Holley did (it was used on the Ford NASCAR entry). Holley has had a Ford throttle lever ever since; and it has to be adapted (you use a special bushing) to work with a Chevy, which still irritates me. One big carb is much easier to tune than two or three smaller ones (which is why I threw a Corvette manifold, three Holley two barrels and the linkage along with the air cleaner in the trash and buried it my back yard when I bought a 1967 427 L-71 motor for my Camaro).

The Holley will not make one horsepower more than a properly tuned Edelbrock (CarterAFB) or a Rochester QuadraJet or a brace of similar size (cfm rated) Weber carbs. All will mix air and fuel to the same ratio of air and gas to burn in the engine. If you want the most expensive carb on the planet that is used in place of EFI on many sports cars because it can be so completely tuned that every part can be tailored to match the car's needs. Four Weber DCOE carbs and manifold for a BBC will set you back $3,600. It won't make any more power than Holley Dominator but it looks totally cool.

Big Dave

 

What do you think about a combo pack like this?

http://www.ebay.com/itm/Edelbrock-2...ake-Carburetor-Kit-/111869118639?hash=item1a0beb48af:g:f~wAAOSwa-dWj8Jx&vxp=mtr

 

What do you think about a combo pack like this?

http://www.ebay.com/itm/Edelbrock-2...ake-Carburetor-Kit-/111869118639?hash=item1a0beb48af:g:f~wAAOSwa-dWj8Jx&vxp=mtr

That is much better than putting a new carb on the boat anchor you have for a manifold now. Some people rag on the Edlebrock carbs so you might want to look at what Summit or Jegs sells that manifold for and them put an SMI QJet on top of it. A properly set up QJet will idle like a kitten, sip gas while cruising, and have more than enough when you floor it. Shop and compare.