Mr. Gasket 8703 Hot Rod Calculator User Manual
Page 47
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Carburetor size — Based on RPM and engine Displacement
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 5,400 RPM. Calculate the
Theoretical, Street, and Race Carburetor Sizes.
KeysTroKe
disPlay
0.
1. Enter your RPM and Engine Displacement:
rPM 5400.
enG
siZe
400.
CU in
2. Calculate the Carburetor Sizes:
THeor
Carb siZe
625.
CfM
**
sTreT
Carb siZe
531.25
CfM
*
raCe
Carb siZe
687.5
CfM
* Repeated presses of
will toggle through the inputs and outputs,
starting with the Volumetric Efficiency.
— do noT Clear CalCUlaTor —
** 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 Carbure-
tor Size of about 688 cfm might be your answer (calculated at 110% of
theoretical capacity). However, it is unlikely that you will find a carbure-
tor 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.
(cont'd)
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