Swap motorcraft 2100 for a 4bbl carb on a 304

[Sc37206]

Do you have to use an adaptor or replace the intake manifold to switch from the stock carb to a 4bbl in a AMC 304 ?

 

[JeeperChris]

If you have the 2100 carb, then you need to change the intake manifold if you want a 4-bbl. An adapter won't do for that kind of swap.

 

[gert]

Edelbrock makes great 4 barrel intakes, the old carter 4 barrels have a narrower bolt pattern than the Holleys, a lot of intakes are made with both bolt patterns just be aware of it.

Also the Q jets and thermoquads are their own animals


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[mriplaybass]

Do you have to use an adaptor or replace the intake manifold to switch from the stock carb to a 4bbl in a 304?

I kind of went the opposite route. I had installed an Edelbrock 4bbl intake when I rebuilt the engine in the event that I ever wanted to go with a 4bbl carb. Fast forward one year, and we decided to go with a Holley Sniper. By that time Holley had come out with a 2bbl version of the Sniper, and I felt it was a far better fit than the 4bbl model would be. So now I sit with a 4bbl manifold, wanting to put a 2bbl Sniper on. What i ended up doing was purchasing a 2bbl to 4bbl adapter from Summit Racing and putting it on upside down. Problem is, that this exposes an area under the Sniper where the gasket is the only thing protruding without 2 surfaces to sandwich the gasket in tightly and prevent any vacuum leaks.
Here is what I did.











The pictures are still with the 2100.
As you can see, the plate that I made, allowed full contact with the gasket. In your case, you would have to put everything on upside down. Anyway, convoluted though this is, if you don't want to replace the intake manifold, this is an alternative. Personally, I think that a 4bbl carb. on a stock AMC 304 is really overkill. IMHO, you may want to just rebuild the 2100.

 

[JeeperChris]

Quadrajets and Thermoquads are two of the best carbs out there for street use and slower trail driving. Their metering circuits are much better than Holleys.

 

[Sc37206]

Thanks everyone! I really appreciate the info!

 

[Sc37206]

Mriplaybass, the top end was redone and I believe they upgraded the cam. Would that warrant the 4bbl? Im happy to keep it stock if there isn’t much of a difference. I’ve heard the converter won’t produce the same results as an actual 4bbl manifold. Do you think the difference would be noticeable? Honesty, the engine already spins the bfg 31’s and will chirp in second if I get in it too much and that’s with a poorly tuned, vacuum leaking carb.

 

[mriplaybass]

With only a mild cam, I would probably stick with a 2bbl. You are right, adapting a 4bbl carb to a 2bbl manifold is more for show than anything else since you are still breathing through the same intake.