What's wrong with using two Edelbrock 500 cfm, or two Edelbrock 600 cfm carbs?  They look good, work good, don't leak fuel after sitting, are relatively inexpensive, and fit the manifold without much ado?  A 500cfm 2V will not give you the gas mileage that a 500 cfm 4V does simply because of the size of the venturies.  Two of them would be worse, and the spacer needed would increase the installed height.    Joe-JDC

JDC

Familiarity I guess.  I've had a few Ford tri powers and they are sweet looking and running set ups.  I have never played with AFBs.  Most of my experience has been with Holley carbs.  There's a first time for everything.

If you can tune a Holley, you can tune an Edelbrock.  The principles are the same and the Edelbrock comes with a fantastic manual so you can learn how it works and therefore, the analogs to a Holley so that you can use that knowledge..


Lawrenceville, GA

Having owned both Edelbrock and Holley’s I’m with Charlie. If you read the manual closely, and for me more than once, they’re probably easier to tune than a Holley. Removing the top to access the main jet (easily done with the carb on the car), and the springs and rods come out the top without removing the top. Those are the “power valve” enrichment. Once you get your head around it, they’re actually easier to mess with. And they run fine for almost any street application. Clearance on your manifold, I don’t have a clue.

I think there’s someone on this site running 2 2 barrels on a 2x4 manifold, but I think he’s using throttle bodies from EFI units.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Thanks for the input.  I should get the 8V manifold this week. AFBs are the most likely candidate. I'm sure they will fit under my hood and I can buy them new.  It looks like I will need to buy two 500 CFMs. From what I read on the Internet, they should work OK right out of the box.  I don't run a choke on my Holleys.  Here in Florida, a well tuned Y Block will start in all weather conditions. I recently went away for the holidays.  When I came back, my engine started dead cold on the first crank.  Cold around here is 40 degrees.  If I do run chokes on my Edelbrocks, do I use one or two?

If doing a pair of two barrel carbs on a Y, I would be doing the Holley 350 cfm versions.  As Joe brings up, the 500 cfm Holley 2V carbs would be on the big side and those carbs are noted for being gas guzzlers as well as having 50cc accelerator pumps which if using two, would have to be modified accordingly.
 
If just trying to keep it simple and looking for the WOW factor, then the 500 cfm Edelbrocks are popular in dual quad set ups and are expected to be very drivable.  If looking for the increase in performance that comes about when using dual quad carbs, the Edelbrock carbs would need their weighted secondary flaps lightened so that the air flow through the secondaries comes in sooner.  You have to remember that those carbs are calibrated for single four barrel use and when using them in pairs, the air flow is cut in half thereby reducing the air flow signal that opens the secondaries in half.  The weighted secondary flaps would need their secondary flap counterweights modified accordingly if wanting the full potential of those carbs utilized.

Lorena, Texas (South of Waco)

Would an Edelbrock AVS work without modification or does it still need to be modified even though it is adjustable?


Lawrenceville, GA

If the 500 cfm 4V carb is available in the AVS version, then the secondary opening rpm is expected to be adjustable.  In the case of the AVS series, the spring tension would simply be lessened to compensate for the reduction in air flow through the secondaries.

Lorena, Texas (South of Waco)

Summit offers the 500 cfm AVS Edelbrock carb without a choke for $341.95 each.  Are these the carbs I should use?  https://www.summitracing.com/parts/edl-1902/overview/

I received my Edelbrock 257 manifold today.  It looks to be NOS.  The guy I bought it from has had it hanging on his wall for years.  He answered a classified ad I ran on this Forum.  Thank you!!