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Double pumper!

Why do you want to do that? I thought a double pumper would give more power than a vacuum secondary carb? what type of carb are you using ?
I run a holley 750 vac sec but have always wanted to try a double pumper. :welcome:
 

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Technical Support Barry Grant
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Can it be done... Most likely yes, however by the time you go through and purchase all of the required parts, and then do the machine work needed you'll be money ahead selling what you have, and purchasing a new carburetor.
 

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You need a new secondary throttle shaft, right side linkages and cams and a vacuum chamber at a minimum. You MAY need a new primary throttle shaft and left side linkages as well.

If you have ever looked at a Holley parts list and tried to compare a vacuum carb with your double pumper, you would never think of attempting this. There are many good 600-700 CFM carbs available used and in good condition

And no, a double pumper for a street driven car is not the best way to go as far as driveability and fuel mileage - unless you do a WOT start at every light. These are race carbs, regardless of the fact that some think it will run better on a daily driver. Bigger (read more gas) is not always better.
 

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Discussion Starter · #7 ·
how about 4 corner idling and a metering block for a vac 700-750 ?
Irelands child said:
You need a new secondary throttle shaft, right side linkages and cams and a vacuum chamber at a minimum. You MAY need a new primary throttle shaft and left side linkages as well.

If you have ever looked at a Holley parts list and tried to compare a vacuum carb with your double pumper, you would never think of attempting this. There are many good 600-700 CFM carbs available used and in good condition

And no, a double pumper for a street driven car is not the best way to go as far as driveability and fuel mileage - unless you do a WOT start at every light. These are race carbs, regardless of the fact that some think it will run better on a daily driver. Bigger (read more gas) is not always better.
 

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ASE Certified Master Machinist
1967 Chevrolet Biscayne 10-71 blown 433 Big Block Chevy, T400 & 12 bolt 3.73 rearend
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bennyoz said:
Why do you want to do that? I thought a double pumper would give more power than a vacuum secondary carb? what type of carb are you using ?
I run a holley 750 vac sec but have always wanted to try a double pumper. :welcome:
This is a common mistake that many people make. The second accelerator pump is used to supply the additional fuel an engine requires due to many factors such as a large camshaft with considerable overlap, a large plenum area and other factors. The second accelerator pump doesn't provide more power. All things being equal, jetting, cfm, metering orifices, etc., both carbs should make the same power.
 
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