Autolite 2100 vs 4100

[br0nc0xrapt0r]

We are dusting off the old horse and getting it ready for daily driver status again. I am sitting here looking at the 1995 SVT cobra engine in the bay of my 69 and I’m wondering if the juice is worth the squeeze in replacing the 2bbl autolite 2100 with a 4100. Now I have never felt like the engine was lacking although it’s hard to really tell with fullwidths and 37”s and the plugs always looked good. I feel like the response is incredibly snappy and I’ve never had an issue off-road even at extreme angles. I got the carb off of my 1974 Ranger 302 bronco. No I am not converting to EFI, we are moving soon to a remote location and we need simplicity in our systems. Anyways I wondered if I could sip less fuel with an easy foot on the 4bbl or get more power at WOT. It used to have a Qjet on it back in the day and I feel like the performance is the same.

 

[73azbronco]

Nope, stay 2100.

Unless you are getting 400 plus hp out of the cobra stay simple.

BTW I use a quadrajet only because it was faster to get a quadrajet custom built and tuned

 

[ol gray mare]

I had the Motorcraft 4100 on my 302 for years. I really liked it. it was the 480 cfm, same as the 2100. The small primaries seemed to improve the throttle response, and the mileage a little bit. I could feel the secondaries kick in at just above 3000 rpm's getting on the freeway. It screwed my mileage improvement, but it was fun and made the merge with traffic easier.

 

[Speedrdr]

It screwed my mileage improvement, but it was fun and made the merge with traffic easier.

Wait, hang on. I thought that the fun factor in our broncos was the whole purpose. Have I been misled?

 

[br0nc0xrapt0r]

I had the Motorcraft 4100 on my 302 for years. I really liked it. it was the 480 cfm, same as the 2100. The small primaries seemed to improve the throttle response, and the mileage a little bit. I could feel the secondaries kick in at just above 3000 rpm's getting on the freeway. It screwed my mileage improvement, but it was fun and made the merge with traffic easier.

Well now that’s got me thinking. I probably will never drive this thing on the highway ever again and it will hardly see 55. We are moving to an island that’s only 55 square miles. So I might benefit from the smaller primaries. It’s a stock 95 5.0 from a SVT cobra mustang so it doesn’t have any wild performance demands for fuel.

 

[ol gray mare]

If you decide to go the Motorcraft route, Mike's Carburetors is a good source for parts. He has about all you'll need and some really good videos.

 

[DirtDonk]

Isn’t the Summit brand four barrel basically an old 4100? What size and CFM are they basing it on?

 

[MarsChariot]

I have resisted contributing to this thread because I have been saying how fantastic the 4100 is for a long time and nobody ever listens to me! I been running the 4100 on the 76 now for over a decade and it is best carb that I have ever had. There are several reasons why. It is basically the 2100 with two extra barrels. That means it has all the same fittings as a 2100, choke, inlet, throttle, vacuum fittings and so on. So no mods are required except for a proper intake manifold. Most people use one of the Edlebrock aluminum ones. Frankly I had two of those and threw them in the trash because I could never get a good seal and was always fussing with it. Instead you can get a proper iron intake from an older model Ford and drop it right in. The other thing about the 4100 is that there is a factory manual that tells you everything you need to know to set it up and tune it. Once you do that, it is rock solid. The 76 fires up hot or cold on the first crank, idles smoothly, and has a reserve in those two extra barrels for when you need it. Otherwise it is just like a 2100. On the other hand if you are just wanting a carb that works with no muss and no fuss, the 2100, just like the 4100, is certainly much better than the aftermarket. I have tried Holley and Edlebrock carbs and all I did was fiddle with them. The 2100 and 4100 just work and fit all the attachments that came on Broncos stock. And there is a manual for it right from Ford.

 

[jckkys]

I agree with both ole gray mare and MarsChariot. The 480 cfm 4100 and OE cast iron intake is the best combo. I like the extra torque of the 351w and the same combo works better on a 351 than any from the after market. It's a little more difficult to find a 69 Mustang 351 4bbl intake but worth it. I tried every aluminum 351 intake and none work as well as the Ford cast iron intake. The only negative is the extra weight but the Bronco doesn't seem to notice it. I use '78 Bronco front coils that were made for more weight. The 2100/4100s even use original automatic choke tubes, with the 289,302 exhaust manifolds. It proves Ford could have easily put 351s in EBs. The oil pan was the hardest part. A talented welder made it happen with a modified 302 EB oil pan.
The 289 gave me all the HP I needed. It just needed more torque.
The Autolite 2100 and 4100 have side hung floats that are better off road. Summit carbs are center hung but other wise have many of the 4100 features. Holley made a 4160 type 4 bbl list 4648 that Ford listed as a factory replacement for Ford v8s. It's also 450 cfm. These are a bit easier to tune than 4100s but not quite as good for an EB.