Carburetor Size Calculator Version v0.5


This is a simple calculator for determining the approximate size of a carburetor. The Size of the engine can be in Cubic Inches or Cubic Centimeters. The RPM entered should be the maximum RPM the engine is to run (you know that RED LINE on your tachometer). The Volumetric Efficiency is a bit more tricky and is at best a guess unless you have had your engine on the dyno. Some starting points might be like this- Note these are for normally aspirated engines where the carb does not sit on a blower or otherwise is used on a draw through blown application.

The last bit of confusion is the carburetor type. This selection give a bit more modern approach to the size. If you have an out of the box Holley, Carter, Edelbrock, or other replacement carb run with the STOCK setting. If you have a race prepared carburetor select the MODIFIED setting. The thinking behind the increase in CFM is that a well prepared race carburetor has a much better fuel atomization and can perform better at lower vacuum ratings then a stock carb so you can use a larger CFM rating.

Race carb info from www.pro-system.com the rest is calculated from the common CFM formula. Another good source of information is dAMBest Carburetors, they make custom billet carburetors and have some very cool racing parts and yes both would be candidates for selecting MODIFIED. As always call an expert at a tuning shop like the above they will give you more information they you will care to know about.

Remember these are ESTIMATES if you are doing stuff at the lower end of the RPM spectrum go smaller, if on the top end go larger. The graphs will help you get a visual range on what size you will need. These numbers do not apply to IR type manifolds typical of Weber carbs. Your on your own with them, and good luck.
Carburetor  Size Calculator
Engine Size
Maximum RPM
Volumetric Efficiency (VE)
Carburetor Type
Carburetor CFM
Carburetor Size CFM
You can zoom the charts by using your scroll wheel on the mouse or selecting an area of interest on the chart with the mouse. Click areas of interest in the charts to see data points of interest. Double click in the chart area to reset its view to see all data.