I have a 68 Firebird that currently has a Holly 650 Dbl Pumper.

Last year I took it in to have a edelbrock 600 placed on it to try it and notice a significant boost in power. The explanation was that the 650 provided to much gas to my 350's engine.

When Spring rolls around this year I plan on buying a new carb and right now they are on sale for $399.00 CAD + taxes for a manual version.

Is this a good buy? Are there suggestions for other makes that I might want to consider before buying this carb?

Looking forward to any assistance that can be offered.

Please feel free to e-mail me direct at barry_murphy@rogers.com

Thanks for your help!

Best regards
Barry

Most everyone on this site will suggest a properly tuned/rebuilt original quadrajet, I'm sure. That's probably the best choice. I understand CFM doesn't matter as much on those. Personally, I have a Holley 600 CFM vacuum secondary, and I'm very happy with it. You don't want any Holley bigger than a 600 on your 350, trust me. I think you already found that out.
Also, I believe that the edelbrock carbs are based on the quadrajets, you may also be able to decrease the jets or something like that, and keep the carb you have. I'll defer that question to someone more knowledgable.

The following is from our website on carburetor selection, perhaps you will find it helpful:

CARBURETOR SELECTION

When choosing a carburetor for your car, a little homework will often pay large dividends. Consider the following questions:

Is your car a 'numbers matching show car'?
If yes, you are generally restricted to the original carburetor or a duplicate thereof.

2. If no, is your car going to be used for sanctioned racing?

If yes, check with the sanctioning body for their regulations.

If no, is your car going to be based on some factory engine (Example. You have a 1966 Pontiac catalina with a regular fuel 389 and two barrel carburetor. You want more horsepower. Consider upgrading THE ENTIRE ENGINE to 1966 Pontiac catalina premium fuel 4 barrel carburetor specifications, or further to GTO specifications.) By duplicating a factory engine, the engineering has been done for you by the factory. YOU KNOW THE THING WILL WORK!
Assuming you answered no to all of the above, you accept responsibility for doing your own engineering, and the following set of questions are designed to help you make your choice. Please remember that any choice you make will be a compromise. You may choose to maximize horsepower, drivability, fuel economy, changability, appearance or initial cost. Maximizing one category will result in reductions in one or more of the other categories.
Is it legal? The Federal Clean Air Act of 1966 took effect with the 1968 model cars. The Federal Clean Air Act applies to all vehicles licensed in all 50 of the United States. Additionally, some states may have emission requirements more stringent than the Federal level, but the Federal level is the minimum in all 50 states. (1998 addition). It is being reported in many publications that California vehicles through the year 1974 are now exempt from smog emission due to California S.B. 42. THIS IS INCORRECT! Remember government 101 (the state cannot override the federal government). SB42 reduced California's more stringent requirements on 1968 to 1974 vehicles back to the Federal level, and removed emissions on 1966 and 1967 California vehicles.
B. Do you want to use a single carburetor or some form of multiple carburetion?

If you wish to use a single carburetor, the following equation can be used for multi-cylinder 4-stroke engines: CFM = (RPM x CID) / 3456. This equation is familiar to most enthusiasts, but understanding the equation seems to be a different story. Most apply the equation for WOT (wide open throttle) to determine the maximum size of the carburetor, which is good, but only half of the story (unless you plan to drive on the street constantly at WOT). For street use, it is also important to use the equation for your normal cruising RPM, and these that CFM figure for the primary side of your 4 barrel carburetor. This will maximize the air velocity (and the primary efficiency) for your cruising RPM. Remember that too large a venturi means too small air velocity, which means a LEAN condition! We have found that, for modern 8 cylinders of 300 CID or larger, almost without exception, a spread-bore carburetor (small primary, and large variable secondary) will perform best on the street. We have a small quantity of high performance Carter spread-bore aftermarket carburetors (with electric choke). These are part number 9800 and are rated 800 CFM (200 primary plus a variable secondary). Also, consider whether the engine is a large displacement high torque, low RPM; or a smaller displacement high RPM engine; and also the breathing capability of the engine. Chevrolet found the small block to like smaller primary and larger secondary. The 1963 Corvette 327/350 used a 575 (225P/350S) CFM unit. Pontiac found the spread-bore 750 did not do as well on a 455 as an 800 (200P/600S). Chrysler used spreadbore 850 (250P/600S) on their 440 engine.

To help you pick the size carburetor for street use, consider the following Carter aftermarket carburetor sizes:

Square-bore (secondary is variable, based on engine demand)

400 CFM – 200 (P), 200 (S)

500 CFM – 225 (P), 275 (S)

600 CFM – 250 (P), 375 (S) (this is NOT a misprint)

625 CFM – 250 (P), 375 (S)

750 CFM – 375 (P), 375 (S)

950 CFM – 375 (P), 575 (S)

Spread-bore (secondary is variable, based on engine demand)

800 CFM – 200 (P), 600 (S)

850 CFM – 250 (P), 600 (S)

1000 CFM – 400 (P), 600 (S)


Jon.

I am running a Holley 600 also. I think it is sufficient for what I need and performs well. I used it to replace a Carter 650.