# FAQ: How To Tell What Carburetor You Have?

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

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%.

## How do you tell what CFM A carb is?

The volumetric efficiency of the engines is a measurable value, and with an adequate carburetor will get the most efficiency out of the engine. The formula to calculate the amount of CFM (cube feet per minute) that a motor needs is CFM= Cubic Inches x RPM x Volumetric Performance ÷ 3456.

## How do I know what Rochester carburetor I have?

All Rochester Quadrajet carburetors are identified by a seven- or eight-digit GM part number. On units made before mid-1968, the part number was stamped around the outside edge of a round metal tag attached to the fuel bowl.

## What size carburetor 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.

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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 you adjust a carburetor?

Here’s How To Adjust a Carburetor

1. Remove the Engine Air Filter. The air cleaner and filter assembly must be removed for you to access the carburetor.
3. (Optional): Hook up Vacuum Gauge.
4. (Optional): Set Baseline.
5. Warm the Engine Up.
6. (Optional): Adjust Idle Speed Screw.

## How much horsepower 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.

## How do I calculate cfm?

CFM = (fpm * area), where fpm is the feet per minute. To find the cubic feet per minute, substitute the FPM value with the area after the area is squared.

## 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 cfm carb do I need for a 454?

Because the 454 is less efficient, it doesn’t need as much cfm, so a 750cfm carb would be fine while a 650 cfm carb would be too small.

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## How do I know if I have Walbro?

According to the Small Engine Advisor site, Walbro identification numbers are normally found on the outside body of the carburetor. Walbro carburetor identification codes are a combination of letters and numbers, WT-160B, for example. Also, the Walbro name is sometimes prominently cast on the carburetor body.

## Are Walbro carbs good?

Only good thing is the carbs are dirt cheap to replace when they foul up. And they will foul up no matter how picky you are with fuel quality. Zama is owned by Stihl or part owned by Stihl and has their main factory in Japan. They are excellent carbs,no better or o worse than the equivalent Walbro.