GM TBI, Qjet or Auotlite 4100?

[gnpenning]

It's not a chevy carb, it is a Rochester. When launched it was highly praised for its abilities. So much so that Ford even used them in some applications.

Rochester is just a parts supplier that sold to anyone. GM just happen to be the biggest customer.

Definitely this^^^^^^.


Yes the 2100 line is a great carb, just some applications require another option. Even Ford thought so.

 

[rguest3]

The Autolite / Motorcraft Carbs are still considered by many to be the best. Many different sizes of the 2B version for just about any size engine. The problem with most carb applications is that a carb that is Too Big is usually the first choice for many to install.

2100, 2150 - What, 10 different sizes to choose from?

4100 - 1.08 Venturi (480 CFM) Great for most, 1.12 Venturi (600CFM) great for larger engines.

The TBI units (Sniper) are much better than they used to be and easier to tune and get set up from the get go. Holley makes a 2B version too which would work great on a 302 or milder 351W.

 

[johnbeck]

I'm looking to put my gas pig 302 on a diet. I've recently had the 302 rebuilt with 289 High Performance grind cam, AFR 165 heads, and the Edelbrock performance manifold with the 1406 650 cfm carb. that the p.o. had on the engine, BC Bronco shorty headers. Pushing the gas peddle feels like flushing a toilet - a hole lot of fuel down the drain. I've heard mentioned of the 4100 carb with a 1.08 venturi, 480CFM. Would that be a better carb. to provide good performance around town(under 5k rpm), with sufficient fuel volume? Maybe the progression from the primaries to the secondaries on my 1406 could be changed for a wider fuel dispersion rate? Forgive my ignorance, I have minimal experience with carburation but feel there must be a carb. out there more suited to my needs. Thanks, John B

 

[Madgyver]

I'm looking to put my gas pig 302 on a diet. I've recently had the 302 rebuilt with 289 High Performance grind cam, AFR 165 heads, and the Edelbrock performance manifold with the 1406 650 cfm carb. that the p.o. had on the engine, BC Bronco shorty headers. Pushing the gas peddle feels like flushing a toilet - a hole lot of fuel down the drain. I've heard mentioned of the 4100 carb with a 1.08 venturi, 480CFM. Would that be a better carb. to provide good performance around town(under 5k rpm), with sufficient fuel volume? Maybe the progression from the primaries to the secondaries on my 1406 could be changed for a wider fuel dispersion rate? Forgive my ignorance, I have minimal experience with carburation but feel there must be a carb. out there more suited to my needs. Thanks, John B

I never really liked those Edelbrock carbs. my opinion.
Go with a smaller 650 qjet it has smaller primaries or the stock 2v Motorcraft. make sure its a dual plane intake for a stronger intake signal, no shared opening..
what's your cam specs?

 

[Broncobowsher]

The nice thing about a Q-jet is they are demand sensitive. If there isn't a demand for airflow, it doesn't provide it. I've owned a boat that had a little 3.8 V6 that came with a Q-jet from the factory. Traditional thought is that is way too large of a carb. Even though the CFM ratings are much higher than other carbs it doesn't matter. They will only flow what the engine can consume. And do a fine job of metering along the way.

 

[johnbeck]

What model number is the 650QJet? Will the linkage hook up simply? Unfortunately I don't have but will obtain from the machine shop the specs on my cam. Do the QJets sit at approximately the same height as the Edelbrock 1406 650CFM carb? I don
't have much room under the hood and don't want to put on a non stock hood. Thanks for the help! John B

 

[Oatmeal]

What model number is the 650QJet? Will the linkage hook up simply? Unfortunately I don't have but will obtain from the machine shop the specs on my cam. Do the QJets sit at approximately the same height as the Edelbrock 1406 650CFM carb? I don
't have much room under the hood and don't want to put on a non stock hood. Thanks for the help! John B

You'll have to run an adapter so, add about an inch to your current set up.
On my 351W, with a drop base filter 3" K&N, I had to flatten the ears of the wing nut and it barely clears!
Hans

 

[blubuckaroo]

Another fan of the q-jets from jet performance. I run em on the 351w's with an offy manifold to get rid of the adapter.

To be a proper critique of a Quadrajet, you need to be from that era.
Quadrajets were faulty in a couple places.
They leaked internally. They had teenie soft plugs that failed to seal the ports.
They had a lot of adjustments, some that were made by bending control arms.
It was known as the "quadrajunk."

It's truely amazing that it's now got a cult following for off-roaders.

 

[DirtDonk]

They did not all suffer from those problems, and there were millions of them running around on the road for decades, mostly without any of those problems ever having cropped up to pester the owner. And since the fixes for those issues have been around and working for almost as long, there are more and more that will never cause any headaches.
And crude or insulting nicknames are sometimes made up on the spot even by those that know nothing of said problems.
Traildisaster, Stupidlift, Heep, etc. Often used to denote an issue, but sometimes done for fun. Or just to be mean and spiteful because they felt like it.
I mean, have you really ever heard of an Explorer exploding? Yet we use the nickname all the time here.

Lots of design issues have made themselves a nuisance on Broncos and other great products. Most get worked out and then enjoyed. Quadrajunks have been metering fuel successfully on Broncos for decades.

 

[73azbronco]

It's interesting to hear people predict future problems and claim you're having problems now. What a load of BS. I've had no problems with OE Ford 2 and 4 barrels. I see no reason to do a GM carb and plenty of reasons not to. AFBs, AVSs, and Holley 4150/4160s work fine for a daily driver and most off pavement driving. None of them are as good as the Ford 2100, 2150, or 4100. Making a Cheby carb run on a Ford is no accomplishment in spite of what some want to think. Ford carbs work OK on a Cheby too. In both cases there's no reason to do it. The 2100s were never a problem. So again, if it's not broke why fix it?
I know the concept of a classic vehicle is hard for some to grasp.

Sigh, your comment is only valid if Ford carbs were 1: readily available 2: easily repaired (no one wants to work on them AND tune them, least no one in Phoenix area), and 3: ford had an altitude compensation dual spread carb. They don't. So no, it is not a load of BS, and the loads of folks racing them and competing with them proves your point is invalid. My classic Bronco lost the original claim about 1976 when PO installed a 351 and AC.
I would have loved an autolite under the hood, none available, none could be tuned in Phoenix. One guy could get me the qjet for half of the cost of an autolite, and tune it.

This guy https://www.carburetorsunlimited.com/ he talked me out of the autolight, never looked back.

 

[73azbronco]

To be a proper critique of a Quadrajet, you need to be from that era.
Quadrajets were faulty in a couple places.
They leaked internally. They had teenie soft plugs that failed to seal the ports.
They had a lot of adjustments, some that were made by bending control arms.
It was known as the "quadrajunk."

It's truely amazing that it's now got a cult following for off-roaders.

Very true, but as with all old things, guys found a way around all those faults, and now they work fine.

 

[blubuckaroo]

Lots of design issues have made themselves a nuisance on Broncos and other great products. Most get worked out and then enjoyed. Quadrajunks have been metering fuel successfully on Broncos for decades.

Even though I agree about the new market use for the old Quadrajet, I prefer Holley's "spread bore" replacement for it.

 

[nvrstuk]

Thanks AZ for responding to the comments from jkkkys about the Autolite. I had one earlier than deleted it.

The Qjet like I've mentioned several times before is almost a variable venturi carb. Broncobowsher mentioned he's used them on small 3.7's successfully. I've used them on 4cyl marine engines with 190 hp extremely well for decades. Great, fully tunable carb. Best off road carb on the market that's why they have such a following. Nobody has ever identified a similar market for Autolites- for good reason..

The advantages of the Qjet do outweigh the Holley tho...

- Center hung float for off camber use w/o stumbling which is the MOST important factor

- Excellent throttle response. Very small primaries that will give much better throttle response than 2bbls or other brand 4 bbls

- MPG. You can't beat the Qjet for mpg. Case in point. On a 2,000 mile round trip journey to wheel the Rubicon with 8 other Broncos my Bronco with a 351W with over 150K miles on it got better mileage than 2 Exploder motors (one w/less than 10k miles), 3 other EFI motors and a mix of 2 & 4 bbl engine combos on EACH fill up all driving together for 10 days.

- Easy to tune for any/all conditions

- Easy to set up for 4cyl or 8 cyl strokers



Hard to justify any other carb when the lowly Qjet can offer all these advantages over the competition. The only one it doesn't offer is it doesn't come in a new, brightly colored box and it needs some tuning to make it the best all round 4bbl, 4x4 carb out there.

 

[blubuckaroo]

Very true, but as with all old things, guys found a way around all those faults, and now they work fine.

Yes, I remember using JB Weld on the soft plugs and repair kits for the stripped threads on the cheesy fuel filter port.
I had my smog license at a Chevy dealer in the early 70's. When they needed rebuilding, the manager wouldn't let us take that kind of time on them. They ended up in the trash.

 

[73azbronco]

Well it was built from all the old parts off other stuff so

 

[Rustytruck]

Very true, but as with all old things, guys found a way around all those faults, and now they work fine.

Quadrajets were a big deal in offshore and other forms of power boat racing back in the day before fuel injection. The only problem is lack of a kick down lever for Fords Automatic transmission. so you have to be a big boy and down shift manually. If you dig up an old Cagle fuel regulator and add it to the mix the carb is nearly unstoppable. the Cagle regulator was designed for the offshore power boat racing crowd. it was quickly accepted by the offroad people. My Quadrajet which was stock on a Pontiac 400 has never gave me issues hot starting or otherwise. Once I changed I have never had to open the hood up ever again for hot fuel issues. I don't miss having to raise the hood to cool off. even with the crappy California gas I run. other than a rebuild kit and changing the balance on the air valve with the adjustment screw it has been run as is. no jet changes and no rod changes. just run it.

My friend used an edelbroc and dumped it after years of modification and we swapped in A Quadrajet straight off a 350 Chevy truck engine and did the same thing. his engine was mildly modified from stock with cam and headers. he wont go back either.
it is just what it is.

 

[nvrstuk]

Kinda like working around:

- vacuum wipers
- 3 spds (no low 1st gear & gear splits
-wipers mounted @ top of windshield
-gas tank that vomits fuel when filling
- gas tank that takes 5 min to fill
- vacuum wipers
- etc, etc

We work around the things that need fixin'.

 

[Hazegray]

Here's a 4100 for sale: https://lascruces.craigslist.org/pts/d/las-cruces-ford-autolite-4100-carburetor/7383240294.html

 

[bmc69]

We have real gas at every station still so that's never been an issue.

I sure wish we did too. The only places within 30 miles that carry non-ethanol gas are marinas.

 

[Oatmeal]

Well,
Picked up a really clean 4100, that came off a running 66 Mustang, rebuilt by the seller (gonna check the float height and settings) and found a NOS Cagle regulator on eBay.
I also ordered a Mike's Carbs electric choke conversion and a pair of float damper springs, in case they're missing or buggered.
I'll probably add a phenolic spacer as a heat insulator (my Q jet always had heat soak issues) and....my Q jet and adapter will probably end up in the for sale section.