Whats a good size carburetor for a Chevy 350?
Choosing the right carburetor size for your Chevy 350 engine is crucial for achieving optimal performance, fuel efficiency, and reliability. Whether you’re building a street cruiser, a weekend warrior, or a track-ready machine, understanding how to size your carburetor correctly can make all the difference. In this article, we’ll break down the factors to consider and provide guidance on selecting the best carburetor size for your Chevy 350.
Understanding Carburetor Sizing
The size of a carburetor is typically measured in cubic feet per minute (CFM), which refers to the volume of air the carburetor can flow. The ideal carburetor size depends on the engine’s displacement, maximum RPM, and volumetric efficiency. For a Chevy 350, which has a displacement of 350 cubic inches, the carburetor size must match the engine’s air demand to ensure proper combustion and performance.
How to Calculate the Ideal Carburetor Size
To determine the correct carburetor size for your Chevy 350, you can use the following formula:
- CFM = (Engine Displacement × Max RPM × Volumetric Efficiency) ÷ 3456
Here’s a breakdown of the variables:
- Engine Displacement: For a Chevy 350, this is 350 cubic inches.
- Max RPM: The maximum revolutions per minute your engine will reach. For example, a street engine might max out at 5,500 RPM, while a race engine could go higher.
- Volumetric Efficiency: This is the engine’s ability to fill its cylinders with air and fuel. A stock engine typically has a volumetric efficiency of around 85%, while a highly tuned engine might reach 95% or more.
For example, if your Chevy 350 is a street engine with a max RPM of 5,500 and a volumetric efficiency of 85%, the calculation would look like this:
- CFM = (350 × 5500 × 0.85) ÷ 3456
- CFM = 474.65
In this case, a carburetor rated at around 470-500 CFM would be a good choice. However, if your engine is more performance-oriented, you might need a larger carburetor.
Recommended Carburetor Sizes for Different Applications
Here are some general recommendations for carburetor sizes based on the intended use of your Chevy 350:
- Stock or Mildly Modified Engines: A 600 CFM carburetor is typically sufficient for most street applications.
- Performance Engines: For engines with upgraded camshafts, headers, and intake manifolds, a 650-750 CFM carburetor may be more appropriate.
- Racing Engines: High-performance engines designed for racing may require carburetors rated at 750 CFM or higher, depending on the specific build and RPM range.
It’s important to note that going too large with your carburetor can lead to poor throttle response and reduced low-end torque, while a carburetor that’s too small can restrict airflow and limit high-end power.
Final Thoughts
Choosing the right carburetor size for your Chevy 350 is all about matching the carburetor’s airflow capacity to your engine’s needs. By calculating the ideal CFM and considering your engine’s intended use, you can select a carburetor that delivers the perfect balance of power, efficiency, and drivability. If you’re unsure or need help with installation, don’t hesitate to consult a professional mechanic or reach out to your local auto service shop for expert advice.
Frequently Asked Questions
Can a carburetor be too big for an engine?
As in life, so it is with carbs: Compromises are called fora fine balance. Not too big because youll lose driveability. Not too small or the carb becomes a major bottleneck. For most hot, dual-purpose cars, pulling about 1.0-inch-Hg manifold vacuum at WOT, max rpm on the dyno isnt far off.
Is a 600 cfm carb big enough for a 350?
Take 350 ci multiplied by 5,500 maximum expected rpm equal 1,920,000. Then, take 1,920,000 and divide this number by 3,456 rpm and get 557 cfm, which calls for a 600-cfm carburetor if you're planning 5,500-6,000 rpm. If you're expecting a maximum of 6,500 rpm, you're going to need a 650- to 700-cfm carburetor.
How do I choose the right size carburetor?
To arrive at the most appropriate carburetor choice, there's a basic formula: engine displacement multiplied by maximum rpm divided by 3,456. For example: a typical 355ci small-block—a 0.030-over rebuild—with a 6,000-rpm max engine speed would work well with a 616-cfm carb ((355 x 6,000) 3,456 = 616.32).
Is a 2 or 4 barrel carburetor better?
One of the main advantages of a 2-barrel carburetor is its simplicity. It has fewer parts and is easier to maintain and repair than a 4-barrel carburetor. This makes it an ideal choice for daily commuting, light-duty hauling, and city driving.
How much horsepower will a 650 cfm carb support?
Typically for the size selection you need to know approx. horsepower (be honest). 600 cfm carbs best suited for low 300hp, 650cfm 340hp-390hp, 750cfm 400hp-460hp, 950cfm 490hp-575hp 1000cfm 575-595, 1050cfm-1250 600hp and up.
How do I know what size carburetor I need?
Take 350 ci multiplied by 5,500 maximum expected rpm equal 1,920,000. Then, take 1,920,000 and divide this number by 3,456 rpm and get 557 cfm, which calls for a 600-cfm carburetor if you're planning 5,500-6,000 rpm. If you're expecting a maximum of 6,500 rpm, you're going to need a 650- to 700-cfm carburetor.
What CFM is a stock quadrajet carb?
Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs.
What cfm is a stock quadrajet carb?
Two basic sizes of Quadrajet were produced over the years; 750 and 800 CFM versions. The 800 CFM unit (identified by a slightly larger primary venturi) was relatively rare, found only on 1971-73 Buicks and 1973 Pontiacs.
What does adding a bigger carburetor do?
Up to a certain point, using a bigger carburetor does add more power…. assuming the engine was originally equipped with one too small to provide all the fuel/ air the engine can use. And while it sounds counter productive, it can actually mean using LESS fuel, if you drive with fuel economy in mind.
What's a good size carburetor for a Chevy 350?
Any 600 cfm carb will do just fine.
