I was tossing around an idea I thought I would throw out for dissection: With the tiny primary bores of the Qjet carb, and the great velocity of the incoming air atomizing the fuel so well, I wonder what would happen if we mixed those characteristics with the 'annular fuel discharge' of the Autolite 4100? (For me, all the 'annular fuel discharge' means is that the boosters on the 4100 discharge the fuel from three orifices, as opposed to one on most carbs.) Smaller diameter squirt means better atomization, right?

Well, I'll bet that if the two of those carbs mated we'd have a nice improvement over what's out there now. What do you think?

 

IIRC annulars are available for Hollys. Might be worth an inquiry to Mr. Ruggles to see if they are available for Qjets.

 

The annual boosters in Autolite carbs have, I never counted and am too lazy to go look at one so I'm guessing, 10-12 holes around the inside to atomize fuel. They're a lot bigger than the downlegs in Holleys and Edelbrocks. Fatter, like a donut. It would probably be tough to squeeze into a Q-jet's little primary bores.

 

Your idea has already been thought of by Pony Carburetors. They make an Autolite 4100 "Spreadbore" carburetor that has the annular boosters that all Autolite 4100s have, but the primary venturis have been sleeved to narrow them down to a smaller size, while retaining the rear venturis original size. This makes for an internal spreadbore carburetor that can be used on any square bore intake manifold.

See here:
Carburetor, Carburetors, Carbs, Carb Parts. Pony Carburetors - Your Ford Carburetor Restoration and Part Sales Specialist


This is what I am running on my own 1985 F150, and I am very happy with it.

 

I had a 4100 on my truck, from Pony. I found them extremely over-priced (all total, about $600 for a 40 year-old carb), and had problems from day one with it. I will say that I averaged 15--16mpg, street and highway, with it. And for a F250 that is great mileage.

What I did not enjoy about the 4100 was the performance. Nor is there any adjustment, other than the jets. That is where the QJ is superior: every function is adjustable. It is a great blend of street/race carb.

 

Although I agree with you in that Pony Carburetors are way over-priced, I disagree with performance. My Autolite (and original Motorcraft 2150) performs much better than my Holley ever did, and my Autolite starts right up every single time with a single pump of gas and stays running with no hesitations at all. I have had people actually tell me that my truck feels like a fuel injected vehicle. My gas mileage went from 12 to 18 when I switched from a Holley 4150 470 cfm to an Autolite 4100 600 cfm.

I hear all these stories about how "superior" the mighty Quadrajet carburetor was and how great they were back in the day. I am too young to remember them, and I have never been in a vehicle that had one. The design of the Quadrajet looks very interesting and intriguing to me. Yet, except at car shows, I NEVER see anyone actually running a Quadrajet. From what I understand, they had one of the worst reputations of any carburetor. All of the Chevy drivers I know toss the Quadrajet in favor of a Holley every time. And I hardly ever hear about someone replacing their Quadrajet with another; it's almost always a new Holley or Edelbrock, which are both spreadbore carburetors. And every single newer design carburetor out there is a squarebore carburetor, NOT a spreadbore like the Quadrajet. Why is that, if they are so "superior?"

 

They also tossed the 4100's for Holley's too. It is always easier to buy a cheap Holley than to take apart a QJ and remedy the problem. The QJ is a complicated carb. And yes, in the early years of production it had some probs, and so got a bad rap. GM, however, used it for almost 20 years, refining it.

Bottom line: I've used both the 4100 and the QJ. The QJ was a bear to rebuild. The 4100 is a walk in the part in comparison. But the QJ supplies better performance and better mpg, if I keep my foot out of it.

 

They have six holes in the booster.

 

I have a couple of 4100's. I might rebuild one, the 1.12 venturi size (600 cfm). It would be interesting to do a comparison between the QJ and 4100 for power and mpg. After spending $600 bucks with pony carbs the last time, I think I'll splurge this time and use the $12 rebuild kit and $8 accelerator kit from Kragen. I'm going all out.

Joke: What is the longest distance in the world? The distance from some people's hand to their wallet.

 

I would LOVE to see a fair comparison between the Autolite 4100 and Quadrajet carburetors.

 

The Perfect Carburetor

I have never seen one of those.
Hope I never have to rebuild another Holly, Carter, Autolite or Q-Jet again. EFI for me.

 

Well, I think the mad scientist in me has gone too far. With my new pin drill set, and lack of experience with the QJ, I think the project has gotten out of control for me. I'm left with a lack of bottom end acc., no matter how I drop in jet size. At this point I am going back to ground zero: A new body of a non cal. qj, with all the orifices, air bleeds, etc., at oem. Car swap meet is tomorrow, so I should round up something.

In the mean time...I refuse to go back to the Eddy! I happen to have two Autolite 4100's (1.12 venturi, 600 cfm)on the shelf, and am rebuilding one. I had a 480 cfm 4100 on it before, so this should be interesting.

P.S. Yeah, I knew I was going to mess up something by tinkering with enlarging orifices, but it was a lot of fun and a learning experience. I was able to drive before and after and see the diff., feel the diff with air bleed restrictions and without. I'm not sweating the cost at all--minimal.