Please explain...at first glance the 2100 and 2300 (350CFM model) look virtually identical except all 2300s have a ported vacuum (i think...). What makes the 2300 carb a "performance' model, and the 2100 not?

coconuteater64,

Since you like your version better......
Why don't you drill yours and tap it for a fitting so you can have ported vacuum?

The ported vacuum just helps the mileage not with how it runs. You should have it tuned to really scoot with out the ported vacuum. In other words, you should have it tuned to scream right now........
If you don't like the way it runs, work on tuning it to run well. That is what drag racers do.....the ported vacuum is just icing on the cake!

Have you done a distributor recurve yet? If not, look into it.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Where would I drill and tap for ported vacuum? This intrigues me. There is a choke mechanism on the side, but I switched over to a manual choke. Please continue to enlighten!

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If it was easy, everybody would be doing it.

Do you have some pictures of the 2100?

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

This is it before installation. In this pic the choke mechanism has been removed so I could convert it to manual choke.

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If it was easy, everybody would be doing it.

About a year late, sorry, but does the Motorcraft 2100 perform well on the 225 if you were to use it as an everyday driver? I bought a '74 Duster to drive back and forth to college that has a Super Six. The engine is good, but the Carter Bbd is badly worn around the throttle shaft. (I can't get it to idle at all because it has such a huge vacuum leak!) I have an old Motorcraft 2100 with a 1.21 venturi size off of a 390 Fe just laying around, but I've heard mixed stories of these working on six cylinders. Basically is the Motorcraft 2100 with the 1.08 or 1.14 venturi the way to go for a low cost carb replacement? Any and all help would be greatly appreciated, thank you.

You're right, the 1.21 is too big. I had a 1.14 on mine and it was still a little large for it, but ran fairly well. I sold it and went with a Holley 350 cfm 2bbl and like it much better. The Motorcraft is a fine carburetor but yours is kinda big. Do what I did and find a Jeep guy to sell it to, then buy a Holley. BTW, this is not a bolt-on-and-go endeavor. You'll need an adaptor.

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If it was easy, everybody would be doing it.

I've found a few adapter plates online, the Jeep guys said they have a problem with leaking but I guess we'll see, I just need to hit a junkyard then and try to find a smaller carb, thank you very much.

I didn't see this posted, but if it was, I am agreeing with you

Manifold vacuum to distributor advances ignition timing as much as the vacuum pod is designed to. With 12 deg btdc and the advance hose hooked up, you aren't actually seeing 12 base, you are seeing base plus vacuum advance equaling 12.

So, what happens is that you step on the throttle, vacuum drops causing advance to drop and retard the timing. This will cause exactly the symptoms you describe, both high idle, and low power below 3000 rpm. It does this because above 3000 rpm in your case, the engine is pulling enough volume to still have vacuum at the amount of throttle opening you are at.

Disconnect the vacuum advance, reset the timing to 12 or wherever suits you, and then see how it does.

~RDE~

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1984 D100 Shorty Custom
Certified Auto Appraiser - RevItUp Classic Appraisals
President - Cherry City Bombers CC
Part of Tyrde-Browne Racing

THOR, you've hit the nail on the head. It got so hot it overheated, something it had never done before. But with the Holley it gets the advance like it did with the stock 1bbl, so I like it. Plus, by selling the Motorcraft I helped a buddy out, even though I sold it at a loss.

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If it was easy, everybody would be doing it.

There is no provision for ported vacuum on any Autolite 2100 models, only on the later model that replaced it, the Motorcraft 2150. Many models had a separate base plate with an attachment nipple for manifold vacuum fitted to it.

Some Motorcraft 2150 models also have metering rods actuated by a cam on the throttle plate shaft, I have never seen them, but from what I understand, they can be fine-tuned to an even greater degree for mid-range response, and they are supposed to be the more desirable model, I have no model numbers.

Here are the flow figures:
number = cfm
.98 = 190
1.01=240
1.02=245
1.08=287
1.14=300
1.21=351
1.23=356
1.33=424

Remember that some sanctioned racing demands a 2-bbl, and many racers with 351 engines use a 1.08 carb. The vacuum reading and air volume going through a racing engines is different, so the flow figures given here are not correct for such an engine.

Fords with the Autolite carb actually used manifold vacuum on many engines. Maybe they used a vacuum pod on the distributor that worked opposite, by actually reducing a high advance with manifold vacuum?

As pointed out by THOR, ported vacuum is only necessary for improving your milage by giving a lot of advance in light load conditions, like driving at constant speed on the freeway, It has no effect on the performance. I have both Autolites and Motocrafts, and the real pain is to get the carb base to have a good seal to the manifold, there is not a lot of material along the base flange on any of these carbs.

I managed to buy one with a warped base, that didn't help either.
Warning: Stay away from buying carbs from Michael Ehrman, he is an opportunistic fraud. If you buy from him, do so through eBay only, so that you have a possibility of getting your money back.

Olaf.

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Aspenized

Some sites that deal with info on Autolites and Motorcrafts:

http://mustangtek.com Fantastic site, wish we had one like that for Mopars...

Ed's carburetor forum

tekatlarge.net/Automotive-Related-Information

Olaf.

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Aspenized