Will a square bore carburetor work properly on a spread bore Edelbrock Performer intake manifold? I thought I heard many years ago that they can accept both patterns but can't find anything on the net to confirm. I don't want to order my double pumper until I know for sure.

Thanks in advance!

 

Simple answer is no. You need an intake with dual bolt patterns to use either carb choice. Maybe you can buy an adapter ( although I can't think of one ) but that will change your intake somewhat because of height.
Here's something you might read i grabbed off WikiAnswers that I think will help you.

Square bore and spread bore are terms used for 4 Barrel caburetors and the matching intake manifolds the carburetors are mounted on. The term(s) mostly describes the carburetor in normal usage but applies to both carb and manifold..

Square bore carburetor's venturi's are of equal size, ie 4 holes of the same diameter. The primaries generally open first , the secondaries open next with vacum or air flow through the carb air horn or sometimes through linkage designed to provid sequencual opening. On some hot rod/very high performance applications all 4 venturi's open together, generally for strictly perfomance motors where fuel mileage is not considered. Square bore carbs generally offer a little more power and a smoother power range.
Spread bore carburetor means unequal in size venturi. These carbs have 2 equal size small venuri's plus 2 equal size large- huge, venturi's. The small venturi's are called primaries and are used for normal low power application, idleing, crusing at highway speeds for just normal easy driving. The primaries generally run a little lean on the jetting. The secondaries are much larger and used when max power is needed. The secondaries begin to open when the throttle is normally somewhere near or past or well past half throttle and open up quite quickly. The secondarie are open by vacum or flow through of air through the air horn, by demand. Rarely are they open by throttle linkage alone except at full pedal. At full throttle both the primaries and secondaries are fully open. The secondaries jetting is normally set richer than the primaries. Spread bore carbs generally deliver better fuel economy. If you drive them hard you soon lose the advantage of the better fuel economy.
The intake manifolds match the bore sizes specifically for each type carb. You can change back and forth between carb types w/an adapter, however there is a small loss in performance potential when the carb and intake maifold are not matched... adapters work but not quite as well as with a matching carb and intake manifold. Edelbrock and others make after market intake maniflods that have large bores for spread bores that will work quite well with both style caruretors.

 

hate to disagree but yes you can. most edelbrock performer intakes are dual bolt pattern, so we really need to know which one you have. also the edlebrock carbs that they sell in combinations are square bore, used with an adapter plate shown below. they are the second item down in the second link.


intakes
http://www.edelbrock.com/automotive_...ormer-sb.shtml

adapters.
http://www.edelbrock.com/automotive_..._spacers.shtml

 

Disagreeing is always welcome, or we never learn.
As I stated the simple answer was no. Not knowing much about what intake he has I guess I should have just held my tongue. I only wanted him to understand the differences between spread and square.
Thanks for chiming in blue.

 

I have part number 3701. Here is a link: http://www.summitracing.com/parts/EDL-3701/?rtype=1

In the description it states that it is "square/spread bore". Does that mean that I can bolt on a square bore carburetor without using an adaptor?

Has anyone tried to use a square bore carb on this manifold without an adaptor?

 

Your Intake is able to accept both styles of Carbs. See the 8 Bolt Holes?
Good luck with your project.

 

OK, cool. Thank you guys very much for the help! I will also order the sealing plate that Blue85205 suggested p/n 3701: http://www.summitracing.com/parts/EDL-3701/?rtype=1

 

If you're installing a Holley-style carb on that intake, you need the adapter, which is nothing more than a metal plate. Without it there can be a massive vacuum leak where the baseplate of the carb won't fully cover the wider rear part of the spreadbore carb flange. Link to the plate you would need:

http://www.summitracing.com/parts/SUM-G1420/

If you're using an Edlebrock/Carter style carb, they are usully wide enough to seal up just fine without an adapter, even though they are technically squarebore carbs.