# Often asked: What Size Carburetor Do I Need For A 305?

## 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%.

## What size carburetor do I need for a 307?

You would not run short of fuel with a 570-600 cfm vac sec carb on your 307 unless you are pulling 7000 – 8000 rpm with it and making about 425 + ponys A spreadbore has smaller primaries and larger secondaries and might give you a bit better fuel mileage if you keep your foot out of it.

## 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 happens if you put a bigger carburetor?

It’s not as simple. 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).

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## 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.

## Is a 650 cfm carb to big for a 350?

If you’re expecting a maximum of 6,500 rpm, you’re going to need a 650- to 700-cfm carburetor. These sizing numbers are only the beginning of carburetor selection—a baseline. A 600-cfm carburetor may perform quite well on a stock 350 Chevy.

## 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.

## How much HP does a carburetor add?

After you fix what’s limiting performance, an Edelbrock Performer intake can add as much as 10 HP. The FAQ forum is a good place to ask questions. There are differences between engines and performance improvements.

## 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.

## Does having a bigger carb make more power?

A larger carb will flow more air/fuel at higher rpm and give more top end and higher peak hp.

## Do bigger jets mean more power?

A larger jet number means a bigger hole and more fuel. A smaller jet number has smaller holes and should be used if your engine needs to run more lean.

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## What size carburetor 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.