I'm in the middle of a getting a new 350 put in my car. In the mean time I'm using the old carb from my 305 but I want to get a new carb in the near future. <p>I know that the carb I have is a 4 barrel but that's it. I was wondering what size carb I should get for my 350 and what does cfm stand for. Thanks!

"Cubic Feet per Minute". It's a measure of how much air flow capacity a carb has.

However, the measurement isn't standardized. The vacuum below the carb base can be varied, and that affects how much air will flow through it. Most 4bbls use the same standard, though.

The formula for getting the minimum sized 4bbl carb is to multiply engine displacement by maximum RPMs you will run, divided by 3456 (an easy number to remember). A 350 spinning to 5500 RPMs will need at least a 557 CFM carb. So, go bigger than that. 650 CFM usally will yield good results on a 350.

If I was to get a larger one, like a 750 would it cause any damage or just guzzel gas?

No damage. It won't necessarily guzzle gas. However, economy and driveability are typically improved when the carb is closer to the minimum size required. Performance improvement with a larger carb is measureable, say 750 vs. 650, but typically not felt (assuming both are properly tuned).

650 will be plenty. I've got a 650DP on my 383. Broke it in on the dyno tonight, gonna make some load pulls tomorrow. I'll let you know what it does. Last motor we put together made 470 with a 650 and the one before that made 515. Both had the shafts milled down and the choke horns milled off and a little port work. We stuck the smaller of the two on the flow bench and it flowed like 720. Mines stock though, so it's still around 650.

I was reading the article How to Choose the Proper Carburetor and Fuel Pump and it said that if you have a healthy 350 you should run at least a 750 cfm. The article went on to say that if you have manual transmission that you should consider a mechanical carb instead of a vacum. Any thoughts on that?

Mechanical secondaries are, in my opinion, superior on all counts in a performance application. The manual transmission factor makes that even more so. Going mechanical secondaries also means you need to avoid over-carbureting, which is simply choosing the carb size based on engine size and lowest RPMs at which you would go wide open throttle. The Holley website has a chart to help with that.

Unless you have a huge cam and high numberical ratio rear end gears, you aren't likely to need a 750 CFM mechanical secondary carb on a 350. The 650 is much more likely to produce satisfaction.