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Old 11-15-2006, 12:38 PM
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Square bore VS. Spread bore

Hi Guys,

Can someone please tell me what the difference is between a spread bore and a square bore? I called summit about a manifold and they asked and I felt stupid not being able to answer the question.

Thank You
Jim

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Old 11-15-2006, 01:04 PM
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Square bore- The 4 barrel carb's front and rear throttle plates are the same size.

Spread bore- The carb's rear throttle plates are larger diameter (like a GM Quadrajet or Chrysler Thermoquad)
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Old 11-15-2006, 06:56 PM
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Here you can see on a spread bore, the secondarys are bigger

http://www.thecarburetorshop.com/Cart9800.jpg

Here, on a square bore, as was said, they are all the same size. It is a little harder to see though

http://site.mawebcenters.com/ksautop..._thumbnail.gif

These show the difference as you would see it from the underside of the carb
http://marineengineparts.com/shopsit...ia/EDL2696.jpg

Adam
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Old 11-16-2006, 03:39 PM
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In this photo, there is a Holley 390 square flange on the left, and a 450 Holley spread bore on the right. A Spread bore has the bores spaced farther apart as compared to a square flange. On a Q-jet, or Thermoquad, the rear bores are bigger, but they don't have to be to make the carb a spread bore. Dan








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Old 08-06-2010, 06:36 PM
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spread bore

Quote:
Originally Posted by JimKramer
Hi Guys,

Can someone please tell me what the difference is between a spread bore and a square bore? I called summit about a manifold and they asked and I felt stupid not being able to answer the question.

Thank You
Jim
when a rocket builder designed a cone for more thrust a speed shop engine builder got the idea to use the concept in a carburetor for better performance.
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Old 08-06-2010, 07:06 PM
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Quote:
Originally Posted by wookie726
when a rocket builder designed a cone for more thrust a speed shop engine builder got the idea to use the concept in a carburetor for better performance.
First- You dredged up a nearly 4-year-old thread and added NOTHING of substance to it.

Second- A rocket uses a NOZZLE for thrust- NOT a cone.

Third- WHAT??
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Old 08-06-2010, 08:57 PM
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Quote:
Originally Posted by cobalt327
First- You dredged up a nearly 4-year-old thread and added NOTHING of substance to it.

Second- A rocket uses a NOZZLE for thrust- NOT a cone.

Third- WHAT??
Thanks cobalt, Classic rookie mistake. He might unregister after that one.
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