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Discussion Starter #1
Could someone please tell me the difference between a square bore and a spread bore. I have a plate that came with my carb (1850s Holley 600cfm)
and they say I should use it. Please advise. Thanks, JD
 

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stinger670 said:
Could someone please tell me the difference between a square bore and a spread bore. I have a plate that came with my carb (1850s Holley 600cfm) and they say I should use it. Please advise. Thanks, JD
on a square bore carb the primarys and secondarys are the same size (dia.) (most, if not all, holleys) BUT on a spread bore carb the primarys are much smaller then the secondarys (quadrajets)
 

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Discussion Starter #3
So why do they reccommend that I use this plate? The secondaries are the same size as the primaries. I would think that the largger secondaries would hit the plate... ???:confused:
 

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What manifold are you putting the carb on? The plate is probably an adapter to fit the square bore carb on a spread bore manifold.
 

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Discussion Starter #5
It is a performance products cyclone manifold....I talked to a gentleman at Lane performance automotive and he said its a decent manifold.
 

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If you have a Professional Products Cyclone (not the Cyclone plus) it's a spread bore manifold. It apparently comes with an adaptor plate to fit your square bore carb.
 
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