Challenger RTA
Well-Known Member
They are a stroke of genius and easy to understand once you know them. I guess that's why some of the newer carbs look very reminiscent of the TQ. IMO there is the right carb for the right application.
Carb recommendations / fit
- Thread starter jebirr
- Start date
surfnturf
Member
I'm running a Street Demon on my 73 340 Challenger that was installed on the factory intake by the previous owner. While it drove okay, I was having issues with strong fuel odors forcing me to drive with the windows up and AC on. In addition, it had a serious bog when transitioning to the secondaries. I just had an old school carburetor guy help me with adjustments and after adjusting the idle bleed, and the flap on the secondaries, you'd think the car is fuel injected. The throttle response is crisp throughout the entire range, and the fuel smell is gone. First time I got on it after the adjustments, it smoked the tires and pulled hard through all 4 gears with no bog between shifts.
Xcudame
Well-Known Member
So even the new carb needs some tweaking sometimes!
I truly believe as a whole, we Mopar lovers are more intelligent than the average crowd and can come to places like FEBO and get our problems solved whether it be a simple Ball & Ball two barrel or six pack setup up or electronic fuel injection. This leads me to believe we can run anything we want and get help here to get it dialed in as we see from post after post for the various topics! As a group, we're pretty dang smart as everyone in this post has proven!
Rock on Mopar brothers (and sisters)!
I truly believe as a whole, we Mopar lovers are more intelligent than the average crowd and can come to places like FEBO and get our problems solved whether it be a simple Ball & Ball two barrel or six pack setup up or electronic fuel injection. This leads me to believe we can run anything we want and get help here to get it dialed in as we see from post after post for the various topics! As a group, we're pretty dang smart as everyone in this post has proven!
Rock on Mopar brothers (and sisters)!
Challenger RTA
Well-Known Member
IMO.This is the one that if you don't have everything right before it. Then set it correctly. You can have problems.
It like a row of Dominoes. One miss set it's a bog! Keeping in mind the engines condition. I know there are other here know better than me.
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540HemiCuda
Well-Known Member
I don't know about some of the other newer carbs, but a former Carter engineer was part of the team that developed the Street Demon and built on the innovations of the old TQs while addressing some of their weaknesses and adding modern innovations.
540HemiCuda
Well-Known Member
It has been my experience that no carb is perfect for a particular combo today whether it be a new out of the box carb, or an original carb tuned for different fuels than are available today.So even the new carb needs some tweaking sometimes!
I truly believe as a whole, we Mopar lovers are more intelligent than the average crowd and can come to places like FEBO and get our problems solved whether it be a simple Ball & Ball two barrel or six pack setup up or electronic fuel injection. This leads me to believe we can run anything we want and get help here to get it dialed in as we see from post after post for the various topics! As a group, we're pretty dang smart as everyone in this post has proven!
Rock on Mopar brothers (and sisters)!
The KEY is to start with a carb that is as close as possible to what the combo wants, is easily tuned, has experienced tuners readily available, has parts readily available, and is competitively priced. Our engines are much more tolerant of an overly rich fuel mixture than a lean one. And richer mixtures have less immediate disastrous potential, which is why so many aftermarket carbs are jetted rich out of the box.
If someone is comfortable with and has the parts and tools for tuning a carb; good for them. I salute them for being in an ever shrinking group. Those guys can take a carb that is not necessarily a good choice for a particular combo and make it work. But for most guys, carb tuning is and always has been, something they would prefer to avoid.......if possible.
Personally, I won't make any comment on anyone's intelligence. How on earth would I know that? I just know that I have never known many guys who want to tune on their carbs. Let alone be fluent in it. Whether then or now. So, for most guys, starting with a carb that is the easiest and straightest path to success is paramount. It was then and still is now.
Challenger RTA
Well-Known Member
That's interesting to know. I know nothing about the Street Demon. Other than what it resembles. I myself have heard no complaints about it. That just might be a testament about it. You always here something bad about something before you here the good. Bad news travels fast!
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540HemiCuda
Well-Known Member
There are a lot of youtube videos on the Street Demons. Most are very positive, but as with all things fuel delivery related, there are also some negative ones, too. Check them out. Here is one introductory video:
Xcudame
Well-Known Member
I'll stand by my comment that we Mopar owners are smarter. In my 45 years wrenching on Mopars, overall the population of Mopar owners are much smarter than the average car enthusiast. And I'd say at least 90% of questions are here on the forum are answered to the complete satisfaction of the original poster. That is what makes FEBO, FABO and FCBO so wonderful.
And really tuning a carburetor is so easy with a vacuum gage and/or rpm gauge.
No one willing to own and drive a Mopar should be afraid to twist any screw on their car. If they are, they seriously need to reevaluate why they own a classic car 50 or more years old. It's more than hoping into a set of wheels and driving from point A to B and back. It's tinkering with it and learning all the great things Mopar got right over the other makes. It's getting fluids on you and your clothes. It's scraps and bruises and a piece of dirt in your eye sometimes when you crawl under it.
Street Demon is a great carb. We all agree I think on that! I bought one when they first came out. I just say don't pass up an opportunity to buy and rebuild a decent Thermoquad. Millions were made and lots are still out there. Peace.
540HemiCuda
Well-Known Member
The OP was asking specifically for information/experiences with the Street Demon and mentioned that he was also considering an AVS. He did not ask for opinions on 'other' carbs, of which there are many. So many that if everyone who had an opinion on 'other' carbs were to respond to him, his head would be spinning.
I hope he got his questions answered through all the cross talk. If he didn't, he should just ask for more clarification....................on the Street Demon. Or the CarterBrock AVS.
I will only say this about the AVS; it was also a good carb........in it's day. But was superseded by the Thermoquad which was a better carb for the changing fuel of the day. It's primary problem today is again, it's difficulty to tune and an antiquated tune in the transitions.
Go to page 13 for the tuning chart for a typical CarterBrock to see just how antiquated they are. At least in my opinion compared to other carb platforms. https://static.summitracing.com/global/images/chartsguides/e/edl-1400_fm.pdf
And just for the record: I am making no judgment as to ANYONE'S abilities or intelligence. I try to address questions that are asked that I have personal experience with. And carburators are one area that I feel that I have extensive experience with. And that includes most of the popular platforms of the last 50 or 60 years.
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I hope he got his questions answered through all the cross talk. If he didn't, he should just ask for more clarification....................on the Street Demon. Or the CarterBrock AVS.
I will only say this about the AVS; it was also a good carb........in it's day. But was superseded by the Thermoquad which was a better carb for the changing fuel of the day. It's primary problem today is again, it's difficulty to tune and an antiquated tune in the transitions.
Go to page 13 for the tuning chart for a typical CarterBrock to see just how antiquated they are. At least in my opinion compared to other carb platforms. https://static.summitracing.com/global/images/chartsguides/e/edl-1400_fm.pdf
And just for the record: I am making no judgment as to ANYONE'S abilities or intelligence. I try to address questions that are asked that I have personal experience with. And carburators are one area that I feel that I have extensive experience with. And that includes most of the popular platforms of the last 50 or 60 years.
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66fs
Member
First of all, we all need to stay within our comfort zones. If Holley works for you, go with that. I'm the Geek that walks through a swap meet, checking the numbers on carbs (original Carters) and don't need a book. Most people will be happy with any good 4 barrel carb. There are few new carbs available. Most are pretty good, but lets face it most are designed and calibrated for a 350 Chevy crate engine. I've always had to "optimize" and "bullet proof" everything, I just can't leave good enough alone. I've also wasted time and money hunting down the "Best" thing. Then it came to me, all this stuff was great in the 60's and still is. I don't need a stroker, aluminum heads, special suspensions, or rear disc brakes. Life is as simple or as complex as you make it. A great carb is truly a thing of beauty, and I will always buy a few numbers whenever I find them. Early TQ's HP AFB's and HP AVS's are in that category. Most used carbs have been reassembled incorrectly by all manner of mistakes and surely could not have run well.
Xcudame
Well-Known Member
A '72 340 Cuda came from the factory with a Thermoquad. And if @jebirr was interested in going with a more factory look, that carburator would be correct for his car and that's why I mentioned it. Especially if the previous owner bolted the AVS on the factory spreadbore intake. There's some folks who care about originality while others not so much. Personally I would like purchasing a '72 340 Cuda with a Thermoquad than any other odd ball carburetor including the Holley Street Demon.
540HemiCuda
Well-Known Member
So, the Street Demon is a "great carb" but is an "odd ball carb"? Only the OP can answer whether that answers his question. But the OP said NOTHING about an OE appearance. That is something that YOU introduced into the conversation all on your own. Then there's the small point that the carb is under the air cleaner and is not visible to anyone UNLESS the owner chooses to reveal it.
Why do you have such an agenda with the old Thermoquads? It seems to border on obsession. Frankly, if someone is comfortable with rebuilding and tuning a carb, there are dozens and dozens that would work. The key in this is that the OP is leaning towards the Street Demon which is a very good choice according to the consensus. And will not need a rebuild at the get go before he could even find out if it needed anything else.
I have not dissed the Thermoquads. They have their place. Just like point ignitions. But for many guys (apparently like the OP) fresh, new designs and calibrations on modern carbs are a better choice. That is all there is to that.
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Why do you have such an agenda with the old Thermoquads? It seems to border on obsession. Frankly, if someone is comfortable with rebuilding and tuning a carb, there are dozens and dozens that would work. The key in this is that the OP is leaning towards the Street Demon which is a very good choice according to the consensus. And will not need a rebuild at the get go before he could even find out if it needed anything else.
I have not dissed the Thermoquads. They have their place. Just like point ignitions. But for many guys (apparently like the OP) fresh, new designs and calibrations on modern carbs are a better choice. That is all there is to that.
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Challenger RTA
Well-Known Member
Thanks for you response. I can read into it. There's a lot of experience that passed through your hands and a few others here.
If you stay in a comfort zone you never learn nothing. I still learn here. If you know your limits that's an other thing. To me that's how I see it. Ask questions, read and try. If you fail you leaned something.
Someone has to start some where. Then it's a test of your experience and patience to help them out.
540HemiCuda
Well-Known Member
Challenger RTA
Well-Known Member
Just to bring it back to the original question. What carb will fit. I'm not that versed in the matter, I can guess. Would like to see a list and there + or - of each if notable.
66fs
Member
Well the OP hasn't posted since March 19, 2026. Hope we did not scare him off.
As for your question, in very general terms there are 2 basic footprints for carbs.
1. Spread bore: ThermoQuad and Quadra-Jet + small triple venturi primary bores, large secondary bores, Air valve secondaries, high cfm rating good fuel economy - requires an adapter on square bore intakes or mods.
2. Square bore: Carter WCFB, AFB, AVS; Holley; Street Demon; Edelbrock + fit square bore intakes, still available new, some have adjustable air valve secondaries, - larger primary bores, usually lower fuel economy, some use power valves to open secondaries that can fail,
This does not include Holley Dominators or spread bore replacement carbs.
I have my favorite carbs, based on my street experience, but that does not include any new carbs. I have no problem getting older carbs to work as well or better than new carbs. + and - depends on the user and/or tuner depending on experience.
The "72" 340 came from MOPAR with a spread bore intake and a ThermoQuad. The "72" 340 Thermoquad is a great carb, supplying very good power, drivability, and economy. It can be used on any small block with a slightly larger cam than a stock 340 cam on down with stock jets and rods.
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