Originally Posted By fast68plymouth
If you look at the venturi and throttle bore diameter for both a 4500 and 4150 "1050" it will be readily apparent they aren't going to flow the same.

Yep. Mr. Smoke meet Mr. Mirrors... they can't BOTH flow 1050 CFM at the same test pressure.

At least one big-name racing carburetor builder doesn't even give a CFM rating the last I heard: Braswell. It's all about venturi size, throttle plate size, and booster style.

Here's a question for you: Which of the following flows the most? They're ALL 4150 carbs with 1.75" throttle plates.

1. BG Demon RS 1.425 venturi & downleg boosters

2. BG Gold Claw 1.500 venturi & downleg boosters

3. QFT/Proform 1.45 venturi & downleg boosters

4. QFT/Proform 1.52 venturi & downleg boosters

5. QFT/Proform 1.59 venturi & annular boosters

6. Holley Ultra 1.58 venturi & downleg boosters

7. Holley Ultra 1.60 venturi & annular boosters


The answer: It doesn't matter.

What does matter is which carb works the best on the track with a particular combination... at least, IMO.