Calculated Industries Hot Rod Calc 8703 User Manual page 43

Lastly, while carburetors come in many sizes, they are not
available in just any size. It is quite possible you won't find one
that is of the exact size you calculated on your Hot Rod Calc.
Carburetor sizes are designated by airflow capacity in cubic-feet
per minute (CFM).
In this example, you want to upgrade your 1968 Pontiac GTO's
carburetor. With all the engine and accessory modifications you
have made, your Ram Air II 400 CID engine makes its peak
horsepower RPM at about 5400 RPM. Calculate the Theoretical,
Street, and Race carburetor sizes.
KEYSTROKES

1. Enter your RPM and engine displacement:


2. Calculate the carburetor sizes:



The theoretical carburetor size of about 625-cfm was calculated
based on the theoretical air capacity at the entered RPM and
engine size (100% theoretical capacity). In this example, you want
to upgrade to an application that leverages your modifications, the
race carb size of about 688-cfm might be your answer (calculated
at 110% of theoretical capacity). However, it is unlikely that you will
find a carburetor in the exact calculated size so you might have
only a couple options in a reasonable range such as a 650-cfm or
a 750-cfm carburetor size.
Notice that a User carburetor size is not included in this example.
This is because a known VE was not entered into the calculator.
ENG S SIZE 400. CU IN
THEOR CARB SIZE 625. CFM
STREET CARB SIZE 531.25 CFM
RACE CARB SIZE 687.5 CFM
H
OT
DISPLAY
RPM S 5400.
R C ™ — 41
OD ALC
0.