# Often asked: How To Calculate Carburetor Size?

## How do I know what size carburetor I need?

The formula for calculating how much CFM (cubic feet per minute) an engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456. Any ordinary stock engine will have a volumetric efficiency of about 80%.

## How much horsepower will a 650 cfm carb support?

So, using your Google-Fu you type “How much power can a 650 cfm carb support?” Well, chances are that you’ll get answers in the 450-470 hp range, but that’s not really the right way to look at it.

## What cfm carb do I need for a 350?

A 600-cfm carburetor may perform quite well on a stock 350 Chevy. However, the minute you start weaving in power adders like a hotter cam, a dual-plane performance intake manifold, and aluminum heads you’re going to need 700-750 cfm.

## How much horsepower will a 750 cfm carb support?

A 750DP on a 330hp-400hp 5.7 with a dual plane intake (performer rpm) is easy to tune and will make max power to boot.

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## What happens if your carburetor is too big?

If the barrels are too big, the loss of air velocity means the cylinder will not fill to its full capacity. An engine with a carb that is too big will put out less Torque and Horsepower. It will be difficult to drive due to poor low-end torque. If you drag race your car, an oversized carb will produce slow 60 ft.

## How do I know if my carburetor is rich or lean?

Q: How Do You Tell if a Carburetor Is Rich or Lean? A: One way to tell for sure is by “reading” the spark plugs. If the plug tip is white, the mixture is lean. If it’s brown or black, it’s rich.

## How do I calculate engine CFM?

The formula for calculating how much CFM (cubic feet per minute) your engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456. Any ordinary stock engine will have a volumetric efficiency of about 80%.

## Does a carburetor spacer add horsepower?

When you stack spacers, you are actually improving their insulation properties, and at the same time you’re getting more horsepower. This type of spacer will increase the velocity of your vehicle’s air-to-fuel charge. This means you’ll build low to mid-range torque.

## Are carb spacers worth it?

Spacers are said to improve air/fuel vaporization through and out of the carburetor. Anytime the air/fuel charge has to turn sharply coming off the carb, it increases the chance of separating the fuel from the air.

## What is a 600 CFM carburetor?

A 600 CFM carburetor can be a great choice for a wide variety of engines. They can be a perfect match for a highly tuned race engine around 300 cubic inches all the way up to a street tuned big block.

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## What size carb do I need for a 383 stroker?

Carburetor For 383 Stroker recommends a 650 cfm carburetor. A 750 cfm carburetor will make the engine more powerful, but it is the largest that should be used unless the engine is being used for racing.

## Will a bigger carb make my bike faster?

A bigger carburetor alone will not make your bike go faster. In most cases, your bike won’t even start or idle roughly with a carburetor that’s too big. For more power, you should look into a full system performance exhaust and rejetting your carb (not replacing it entirely).

## How do you increase CFM on a carburetor?

In just a few minutes working with a file, you can augment this mod by applying a radius to the top edges of the choke horn. This increases the flow about 3 to 5 more cfm. You may see carbs that have been reworked for a higher performance by milling off the choke horn.