4 bbl carb on wrong? - Page 2 - JeepForum.com
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post #16 of 71 Old 06-10-2021, 09:37 AM
gutthans
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Quote:
Originally Posted by mudbfun View Post
That is incorrect. If both primarys are on the same plane then they will both only be feeding half of the engine!
John has already addressed this, but you should go back and look closer at the two manifold designs you are trying to compare. Your comment applies to the V-8 design where cylinders are opposed and that runner orientation is not at all what happens on a straight six!

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post #17 of 71 Old 06-10-2021, 09:59 AM
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Hi, I'm with Kevin CJ7.. It looks like a Spread bore carb and a square bore intake.. that's the first thing I saw.. Everyone keeps talking about orientation .. No matter how you orientate it its not going to work with that intake or adapter. You need a spread bore to square bore adapter to make it work.

Spread bore means that the secondary are bigger than the primary and Square bore all 4 openings are the same size

good luck
tim
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post #18 of 71 Old 06-10-2021, 10:11 AM
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Not sure what people are seeing, but the carb is a square bore edelbrock performer/carter AFB. Definitely not a spread bore carb.


85Tuxedocj7, can you get a picture/the numbers from this location on the carb? That will tell us the size and give a starting point to if the carb is too big or other suggestions.
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post #19 of 71 Old 06-10-2021, 10:24 AM
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Quote:
Originally Posted by Fourtrail View Post
Not sure what people are seeing, but the carb is a square bore edelbrock performer/carter AFB. Definitely not a spread bore carb.


85Tuxedocj7, can you get a picture/the numbers from this location on the carb? That will tell us the size and give a starting point to if the carb is too big or other suggestions.
It's hard to tell because of perspective aberration but if the gasket opening is trasoidial shaped then maybe it is a square bore but it appears the secondaries are a bit wider than the primaries comparing how close the secondaries comes to the edge of the remains of the gasket.

1-spreadbore-not.jpg

There always is a chance of the secondaries are just wide enough to fit in the spacer openings and the primaries are smaller then the spacers opening so all the valves could work.
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post #20 of 71 Old 06-10-2021, 10:25 AM
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Quote:
Originally Posted by jeepdaddy2000 View Post
I stand corrected and owe gutthans an apology.
My depth of knowledge of 4 and 6 barrel intakes is showing.

Ditto. I defer to Johns expertise.



Re; the spread bore. It may be possible to overcome a carb to manifold mismatch via a different spacer. ??
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post #21 of 71 Old 06-10-2021, 10:32 AM
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Quote:
Originally Posted by John Strenk View Post
It's hard to tell because of perspective aberration but if the gasket opening is trasoidial shaped then maybe it is a square bore but it appears the secondaries are a bit wider than the primaries comparing how close the secondaries comes to the edge of the remains of the gasket.



There always is a chance of the secondaries are just wide enough to fit in the spacer openings and the primaries are smaller then the spacers opening so all the valves could work.

Bad camera angle, that is an edelbrock square bore base plate. Plus any spread bore has an exaggerated difference between the primary and secondary butterflies.





Edit: if it is a very early Carter AFB, there were a few that had slightly smaller primary butterflies, but they were still a square bore design and should work just fine with that manifold as the secondary butterflies are still smaller than the bore in the intake.

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Last edited by Fourtrail; 06-10-2021 at 10:39 AM. Reason: clarify possibly slightly smaller primary bores
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post #22 of 71 Old 06-10-2021, 10:36 AM
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Quote:
Originally Posted by mudbfun View Post
Ditto. I defer to Johns expertise.
That would be a mistake!!


Quote:
Re; the spread bore. It may be possible to overcome a carb to manifold mismatch via a different spacer. ??
dont need one....

See fourtrail picture
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post #23 of 71 Old 06-10-2021, 10:37 AM
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Quote:
Originally Posted by Fourtrail View Post
Bad camera angle, that is an edelbrock square bore base plate. Plus any spread bore has an exaggerated difference between the primary and secondary butterflies.


Yeah, that looks like it.

Small difference in throttle plates size but center of throttle plates are 'square'

a spread bore has spacing of center of throttle plates way different. Not just size difference


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post #24 of 71 Old 06-10-2021, 10:40 AM
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Quote:
Originally Posted by gutthans View Post
John has already addressed this, but you should go back and look closer at the two manifold designs you are trying to compare. Your comment applies to the V-8 design where cylinders are opposed and that runner orientation is not at all what happens on a straight six!

Affirmative. My apologies. That design is VERY different then the ones I am familiar with. Especially the narrower runners for the primaries. It will be important to get that orientation right. Learning is good! Thank you!
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post #25 of 71 Old 06-10-2021, 10:45 AM
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HI .. I still say the carb is a spread bore.. Look at the center divider of the carb.. One is smaller than the other.. I have a square bore Edelbrock and just looked at the bottom and both are the same size. In his picture of the actual carb one is smaller than the other (spread bore).. My square bore also has 4 bolt down holes..

He needs a spread bore to square bore adapter

good luck
tim
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post #26 of 71 Old 06-10-2021, 10:50 AM
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Quote:
Originally Posted by pedal2themetai View Post
HI .. I still say the carb is a spread bore.. Look at the center divider of the carb.. One is smaller than the other.. I have a square bore Edelbrock and just looked at the bottom and both are the same size. In his picture of the actual carb one is smaller than the other (spread bore).. My square bore also has 4 bolt down holes..

He needs a spread bore to square bore adapter

good luck
tim

All he needs to do is place the spacer on the carb upside down and try opening the butterfly's up. Ez issue to resolve.
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post #27 of 71 Old 06-10-2021, 10:51 AM
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Quote:
Originally Posted by John Strenk View Post
It's hard to tell because of perspective aberration but if the gasket opening is trasoidial shaped then maybe it is a square bore but it appears the secondaries are a bit wider than the primaries comparing how close the secondaries comes to the edge of the remains of the gasket.

Quote:
Originally Posted by John Strenk View Post
Yeah, that looks like it.

Small difference in throttle plates size but center of throttle plates are 'square'

a spread bore has spacing of center of throttle plates way different. Not just size difference

Which is correct for the 'square flange' Edelbrock 500 cfm carb. either way, it still should not need a spread bore adapter as the butterflies are still smaller than the intake bores. That carb is designed to bolt directly to a square bore intake.


https://www.edelbrock.com/performer-...-egr-1404.html
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post #28 of 71 Old 06-10-2021, 10:55 AM
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Quote:
Originally Posted by pedal2themetai View Post
HI .. I still say the carb is a spread bore.. Look at the center divider of the carb.. One is smaller than the other.. I have a square bore Edelbrock and just looked at the bottom and both are the same size. In his picture of the actual carb one is smaller than the other (spread bore).. My square bore also has 4 bolt down holes..

He needs a spread bore to square bore adapter

good luck
tim
I think the primaries are probably smaller than the opening in the manifold and the secondaries probably match the opening perfectly.

A spread bore adapter are much much bigger


The throttle plates would not line up.


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post #29 of 71 Old 06-10-2021, 11:07 AM
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Quote:
Originally Posted by John Strenk View Post
I think the primaries are probably smaller than the opening in the manifold and the secondaries probably match the opening perfectly.

Covered in my post just before yours, come on keep up John...
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post #30 of 71 Old 06-10-2021, 11:18 AM
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Quote:
Originally Posted by John Strenk View Post
I think that depends upon the manifold design.

On some manifolds it helps with smoothing the airflow out the carb giving it a chance to mix properly.

If the base of the carb is mounted on a manifold that instantly changes direction to the left and next instant to the right, you going to get different mixtures in either direction.

Smooth air flow out is just as important as smooth air flow in for "drivability"

If you only run at WOT then that changes everything also as opposed to driving to the grocery store during the week.

Most of my engine performance know how is from working on Chevy small blocks. Clearly not everything is equal across the board, but some basic things will always apply.

I agree that in some cases they could be beneficial for better fuel atomization and distribution depending on the manifold, carb and so on. Either way I dont think the performance difference from a spacer is anything earth shattering though, and in most cases it is hardly noticeable. If it were just a case of getting the carb height correct for the purpose of attachments I wouldn't hesitate to use one.
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