Technical Carburetor adapter question

I have an edlebrock spread bore intake and an edlebrock 650 cfm square bore carb. I see al lot of adapters , but seriously, the carb seats well with no air gaps. Is the adapter necessary?

 

Does the linkage work good all the way to wide open?

 

I have seen quite a few spread bore intakes leak with square bore carbs at the outside edges of the secondaries. They do make a flat plate to use under the carb so you can use a spread bore gasket on the bottom and square bore gasket on to.

 

Are you positive the square bore carb fits perfectly with good overlap on the spread bore manifold?

Not sure about the edlebrock carb but my experience with a Holley square bore was that there is one section where the carb only just barely mates / overlaps with the manifold.

When you first put them together all is fine but eventually as there is only minimal contact surface the gasket sucks in and you have an air leak. Which can be troublesome to find as it is under a part of the carby you can't easily see.

Perhaps edlebrock corrected this with their design but worth a second look and explains why you need an adaptor with some setups

 

I am thinking that I had to use and adapter when I put the 650 Edelbrock on the 2110 spread bore intake but that has been a long time ago.
update at 17;28
The instructions say you do have to 1400 - Performer Series Smog Legal Carburetor.qxp (edelbrock-instructions-v1.s3.amazonaws.com)

 

I'm with @greybeard360 , flat plate(gasket sized) to seal off the thin sealing surface. I don't even think it's .125" thick.

 

do you have this?

https://www.edelbrock.com/square-bo...e-100-thick-for-edelbrock-manifolds-2732.html

you should...

 

Yep, I do believe I’ve seen a couple floating around out in the shop...someplace.

 

My sbc had a 1406 Edelbrock on a spreadbore intake with an open adapter on it. Troubleshot a vacuum leak and found the adapter was not sealing completely to the intake. Installed a 4 hole adapter recommended by Edelbrock and problem was solved.

 

So as I’m looking into this, I figured I would buy a spread-bore to square bore adapter made from phenolic or similar material to reduce heat transfer to the carb. Oddly enough, I can’t find one. They’re all aluminum, or steel. Anybody seen one....ever?

 

I've never seen one, you would have to get one that fits either the carb or the intake and then use the plate that Jim posted the link to in post 7. You should be able to get one of those plates off the speed trinket wall at any O'Reilly's as they are a really common item. Worse case they can get one in on the next truck from the warehouse. Just about everyone who has put an Edelbrock carb on a Q jet intake has one laying around but sometimes they don't let the linkage clear the manifold such as on a cast iron Cad 425/472 or 500 intake.

 

Carb flange adapters need to have some strength....phenolic spacers work because they're just under compression. So it doesn't surprise me that you can't find one.

 

I notice that this one has phenolic inserts that may help with heat issues........
https://www.amazon.com/Spectre-Perf...to+square+bore+adapter&qid=1629301122&sr=8-10

Any of the adapter kits can be more prone to leak than matching a spread carb with a spread intake, or a square/square, because of the thin spot on the adapter. But leaks are the exception because they usually work just fine.