Choosing a carburetor

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*Mechanical secondaries are generally best suited to light, manual transmission vehicles or automatic vehicles with the correct stall speed torque converter and correct rear gears to match the engine and carb.
 
*Mechanical secondaries are generally best suited to light, manual transmission vehicles or automatic vehicles with the correct stall speed torque converter and correct rear gears to match the engine and carb.
 
*Mechanical secondaries are preferred for racing applications. In some cases the fact that the secondary jets can be changed in the double pumpers and there's an extra accelerator pump to deal with, some may find it harder to tune than the simpler 4160 type Holley. But once the process is understood the tuning becomes much easier, plus the added adjustability that was a hurdle at first becomes an asset. The 4160 needs the metering plate replaced or modified to use jets if the secondary air/fuel ratio is off.  
 
*Mechanical secondaries are preferred for racing applications. In some cases the fact that the secondary jets can be changed in the double pumpers and there's an extra accelerator pump to deal with, some may find it harder to tune than the simpler 4160 type Holley. But once the process is understood the tuning becomes much easier, plus the added adjustability that was a hurdle at first becomes an asset. The 4160 needs the metering plate replaced or modified to use jets if the secondary air/fuel ratio is off.  
 
  
 
==Selecting carburetor brand==
 
==Selecting carburetor brand==
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'''*'''The model 4160 is a vacuum secondary carb- w/few exceptions, one is the 0-4224 660 cfm "center squirter" carb, originally designed to fit on a dual four barrel intake end-to-end. Another is the 450 cfm 0-9776 Model 4160 mechanical secondary carb. It has no secondary accelerator pump. These carbs are designed to be used in a multiple carb application. They have no choke flap, they have side hung float bowls and single fuel inlet. The model 4150 can be either a vacuum secondary or a double pumper carb.
 
'''*'''The model 4160 is a vacuum secondary carb- w/few exceptions, one is the 0-4224 660 cfm "center squirter" carb, originally designed to fit on a dual four barrel intake end-to-end. Another is the 450 cfm 0-9776 Model 4160 mechanical secondary carb. It has no secondary accelerator pump. These carbs are designed to be used in a multiple carb application. They have no choke flap, they have side hung float bowls and single fuel inlet. The model 4150 can be either a vacuum secondary or a double pumper carb.
 
  
 
You may hear a Q-jet being called a 'mechanical secondary' carb. And to some extent this is true- the secondary throttle blades WILL open when you floor it if the choke is off. But- and this is an important 'but'- it's the air valve at the top of the carb that works on the 'as needed' basis. The Edelbrock/Carter is a similar design in that the secondary throttle blades will open if floored, but the Edelbrock/Carter uses a air door that works by the amount of air flowing into the secondary side and it too, won't give the engine any more airflow than it needs.
 
You may hear a Q-jet being called a 'mechanical secondary' carb. And to some extent this is true- the secondary throttle blades WILL open when you floor it if the choke is off. But- and this is an important 'but'- it's the air valve at the top of the carb that works on the 'as needed' basis. The Edelbrock/Carter is a similar design in that the secondary throttle blades will open if floored, but the Edelbrock/Carter uses a air door that works by the amount of air flowing into the secondary side and it too, won't give the engine any more airflow than it needs.
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The following will give some insight into the various makes and models of carbs that are readily available.
 
The following will give some insight into the various makes and models of carbs that are readily available.
 
  
 
=='''[http://www.holley.com/ Holley]'''==
 
=='''[http://www.holley.com/ Holley]'''==

Revision as of 02:47, 22 May 2012

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