carb cfm rehash?
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Tuned
Joined: Oct 2003
Posts: 386
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From: Wichita, KS
carb cfm rehash?
ok so I have 2 carbs that are stamped 1.21 which is around 351 cfm according to the charts. but one is a 80's model and the venturi's are the same size but the lower butterflys are considerably smaller than the 68 model. so my question is. are they bothe really 351 cfm or are the newer models rated different?
Posting Guru
Joined: Aug 2000
Posts: 1,127
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From: (near) Denver USA
The rating methods should be the same for newer and older carburetors.
Bear in mind, the airflow numbers given in the list are a "rule-of-thumb," based only on the diameter of the main venturis.
The actual airflow capacity is influenced by several other factors, including the size of the booster venturis, throttle bore diameter, airhorn/choke tower contours, etc. These may vary from one 2100/2150 version or calibration (i.e., carburetor ID code) to another, even with the same main venturi diameter.
If all other components are identical, the carb with larger throttle bores will flow more air.
I've seen stock 2150s with 1.21" main venturis that flowed at various rates from 325 to 370 cfm.
Unless you can find a published rating for a specific carb version, the only way to determine the airflow capacity is to measure it on a flow bench.
Bear in mind, the airflow numbers given in the list are a "rule-of-thumb," based only on the diameter of the main venturis.
The actual airflow capacity is influenced by several other factors, including the size of the booster venturis, throttle bore diameter, airhorn/choke tower contours, etc. These may vary from one 2100/2150 version or calibration (i.e., carburetor ID code) to another, even with the same main venturi diameter.
If all other components are identical, the carb with larger throttle bores will flow more air.
I've seen stock 2150s with 1.21" main venturis that flowed at various rates from 325 to 370 cfm.
Unless you can find a published rating for a specific carb version, the only way to determine the airflow capacity is to measure it on a flow bench.
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