The stock throttle bore size at the carburetor flange is 1.500”.  The replacement 465 cfm Holley carbs for the 1957 Thunderbird match this perfectly.  To use some of the newer aftermarket carburetors, it will be necessary to either enlarge those bore sizes or use a carburetor spacer that accommodates the throttle bore size of the carb that’s being used.  The throttle bore size of most 600 cfm carbs is 1.560” while the throttle bore size for 750 carbs is 1.690” and 1.735” for 850 carbs.  In a perfect world, it’s desired to not have any ‘ledges’ in the flow path.

For additional performance, there is an advantage to machining the four holes at the carb flange to a two-slot configuration.  The slots are made larger to accommodate the later model carburetors. This by itself is worth ~6 HP without any other mods or porting to the manifold.
 

 

"Would you be able to modify my manifold?  My 292 is stock, are there any other porting mods for the manifold?"

Well, yes and no. Yes, the 57/ ECZ-B can be modified for a later style carb (larger throttle bore size). No, if wanting to mount a later style carb on your present intake as it would require an adapter and could not be used on a BIRD due to hood closing (carb mounting being too high).

Also, there should be no problem using the 57/ ECZ-B intake on the 55/56 cyl heads as FORD lists the same intake gaskets for all three years (subject to correction) (also would be nice to know all years component runner sizes).

Why do you want a later style carb? You will also have to go with a 57/ DUAL ADVANCE DIST and that will require a 12V upgrade due to losing the proper 1955 LOAD-O-MATIC carb signal.

Hold off until this thread is reviewed/answered by TED EATON as to the best/easiest way out.            

If its was me ...  ... I would try and find the correct 1957 H4150 core and rebuild or have rebuilt the HOLLEY as the OP still has to consider the needed 1957 TV LINKAGE changeover (from 1955 H4000) if a F/M.

That and the proper phenolic spacer (OEM on 57 FORD and BIRD H4150 - B7AZ 9A589-B)

Another thing to consider, is the 1955 ACL ASSY oil bath or dry.

"I’ve converted my ‘54 239” to the ‘57 and up distributor, must be close to 20 years ago. I’m still 6 volt. Used the points and condenser from the ‘57 and up distributor."

... hmmpf ...

THANX for the reply.

So no point (12V) burning, pitting or condenser failure(s).  6V coil and no overheating? It keeps the plugs clean?

Cheap quick way out of the LOAD-O-MATIC.    

While the actual slotting of the holes can be performed by the do it yourselfer, machining the flange flat does require some form of milling operation.  Due to shipping costs, it’s always worthwhile looking for a local machine shop that can do this operation as shipping costs can easily outweigh the actual machining operation.  But yes, if the manifold is shipped to me, I can do that slotting operation to it.  Just email me directly regarding doing that.

Here's some more info about FYB intake manifolds in general.

Ford did an extremely good job in matching the air flow requirements of the ECZ-B intake manifold to that of the 1957 heads and camshaft.  Issues with that factory air flow in the ECZ-B manifold occurs when the camshaft is upgraded, the cubic inches are increased, the compression ratio is increased, and/or any porting in the cylinder heads takes place.  When any of this takes place, the ECZ-B manifold is then lacking in air flow to keep up with any of the aforementioned changes and then requires modifications in order to keep up with the revised flow requirements.

While talking about intake manifold air flow requirements, I have tested both the ECZ-A (Teapot) and ECZ-B manifolds in a back-to-back dyno test and the ECZ-B handily wins this contest.  In this particular test, a dead stock ECZ-B manifold is worth 27 horsepower over the ECZ-A manifold.  Both intakes were tested with a 750 cfm Holley carb.  Ledges at the carburetor flange was evident in both instances so there’s more to be had in both instances.

When I modify the ECZ-B intakes so that they are dual slotted, I typically do that so that the larger bore carburetors fit without ledges or flow restrictions at the entry point of the manifold.  If using a carburetor spacer, then the sizing of the holes within the carb spacer are taken into consideration.  For most of these modifications, I use a Moroso P/N 64930 four hole spacer as the template for hole placement and general sizing.  As Kultulz brings up, the ’55-’57 Thunderbirds are not carb spacer height friendly so take that into consideration.

In machining the Mercury 8 Restorations (M8R) aluminum 4V intake manifold entry bores from the as supplied 1.510” to the 1.783” size, there was an 8 HP increase.  Very significant increase and without making the entry slotted.  That manifold was tested in both bore size configurations with the aforementioned Moroso 1” 4 hole spacer but had a ledge or flow restriction at the carburetor flange with the 1.510” throttle bores.  The increase to 1.783” simply had the throttle bores in the intake manifold matching the carb spacer which was then topped off with a 750 cfm Holley also with 1.783” carb bores.  Here’s a picture of the M8R intake before enlarging the throttle bores.