65 T-Bird carb swap to Edelbrock AVS2 650CFM

[michal300th]

I'm planning on swapping my original 4100 Autolite carb to either one of the following:
Edelbrock AVS2 (leaning towards this one): https://www.edelbrock.com/avs2-650-cfm- ... -1905.html or Edelbrock 1405: https://www.edelbrock.com/performer-ser ... -1405.html

I will be installing it onto stock/original 4 hole/barrell intake manifold (C5AE9425C).



I'll most likely get rid of the PCV/coolant heated spacer underneath the carb, replace it with heat insulating spacer and run the coolant hose straight to heater core, bypassing PCV plate.

I'm not sure what spacer & gaskets I should use, so would greatly appreciate support :) I think best would be to use the 4 hole spacer and gaskets.



Edelbrock AVS2 has differently sized bores; primary 1.44" & secondary 1.75". My concern is that the bores on the spacers might be too small for the throttle plates on the bottom of the carb to fully open. Could that happen, or do such spacers come in universal bore diameters that clear most carbs?

If that spacer setup wouldn't work, could open center spacer (square bore) be installed on 4 hole manifold instead? Would it downgrade the performance in any way? Curious to hear from those who have Edelbrock carbs installed on the original 4 hole intake manifolds, how they dealt with their setup.

[Alan H. Tast]

If you have access to a die grinder, Dremel motor tool and related cutting heads, you could enlarge the bores in the aftermarket spacer - place the spacers against each other, take a pen, scribe or ? and draw the bores for the original spacer onto the replacement spacer.

NOW, don't forget your original spacer has a taper to allow the carb to sit level, as the original manifold's carb base is tilted for use in a full-size Ford/Mercury application. You will really need to replicate that taper. The better solution may be to get a thin spacer with the OEM coolant-heated spacer, and block off the openings for the heater hose connections.

There's a reason why Ford's engineers had a heated spacer in the mid-'60s - the heated spacer allowed for faster warmup of the carb and worked quite well in its time. As for the carb swap, personally, I think the Ford/Autolite 4100 is one of the most bullet-proof and simple 4-barrel carbs to rebuild and maintain, provided it gets a THOROUGH rebuild, including rebushing the throttle shafts to eliminate vacuum leak sources due to years of wear. Altering the spacer will have an effect on your fuel economy, performance and cold-hot starts, and may have unintended consequences versus what you think the benefits will be by thermally isolating the carburetor from the rest of the engine.

[jtschug]

You should probably buy a carb with an electric choke, they aren't that hard to hook up.

The open spacer will work fine, I had to cut out the center of my spacer because the butterflies were hanging up on the holes, but I've got a 720 CFM Barry Grant Demon, so the butterflies on these are a bit smaller.

You will need a new air cleaner because the original Ford air cleaner will not fit the Edelbrock. I had one of those for a while, and I could not get the original to fit.

[michal300th]

Thank you Alan and jtschug. Alan you’re right, the coolant spacer is wedged… Which makes things complicated. The reason I wanted to swap carbs is because a good rebuild here in Poland would cost almost as much as a new Edelbrock. Yet I’m still worried if it would’ve been rebuilt the right way (throttle shaft bushing, leveling the bottom of the carb, etc.) and not just cleaning and parts replacement.

How on earth people install the aftermarket carbs without slanted spacer on this wedged intake manifold… I’ve seen such swaps… A friend of mine has the same intake manifold and the carb is angled, since he never did anything to the aftermarket spacer. Yet it runs fine with the same Edelbrock carb.

jtschug how did you solve this? Did you do anything to your spacer to make the carb sit flat?
Thanks!

[jtschug]

I used the plastic 1966 tapered spacer from Birdnest. Ford didn’t use the coolant spacer in ‘66