[valiant67]

You have a few options.
1) the Thermoquad can be rebuilt. There are kits around to that, but it’s a complex carb. There are people who can make these carbs work.
2) find another Thermoquad better suited to your engine, will probably still need rebuilt.
3) find a new spread bore replacement carb.
4) find a new square bore carb. Best to change to a square bore intake, but there are adapters to do this.

Properly set up, the Thermoquad is a great carb.

 

[LouJC]

If you have a square bore intake the Edelbrock should work, its basically an updated Carter design minus the plastic carb bowl. That or any appropriately sized square bore Holley.
I'm not a fan of buying "reman" carbs on line because sometimes they are combinations of various carbs that don't work well together, as in many reman Quadrajets. If you have a good original core, hold on to it and find a local hot rod shop who can rebuild it, if not a new Edelbrock is the next best choice. Lots of support is available with them just like Holley. I have an original Quadrajet on my boat and kept it all this time because I was able to rebuild it myself when needed. But would not trade it for a 'reman' under any circumstances....
The only thing that would keep me from rebuilding an original core is if it had bad internal corrosion. My Qjet was a bit corroded on the outside (water cooling hose popped off and sprayed salt water around th engine some years back) but when I took it apart it was immaculately clean inside so I put a rebuild kit in it and its been fine.

 

[valiant67]

Another thing - some 1980 carbs had additional emission controls on them and don’t function well without the corresponding input. You should probably find an earlier carb.

 

[sherms]

Awesome thanks so much for the replies guys, would like to keep the intake manifold if possible do I need an adapter to run a spreadbore? Guy at my local parts shop suggested a spreadbore Holley QJet no. 080555C but the list price seeemed really, really steep to at $1083 cad. Was hoping there was a straight bolt on carb that will work without an adapter if possible, but if there's one that more suited to the 383 than the old tq using an adapter I'd be into that too.

 

[sherms]

Also not really looking to rebuild, I definitely dont have the know how or experience to do it myself and would rather not have to find/pay someone to rebuild it.

 

[LouJC]

Does your Mopar have a spread bore intake manifold? If so then the spreadbore Holley makes sense because you won’t need an adapter. They can be bought for less than the price you quoted. Its seems odd it would have a spread bore intake although I have read that some Mopars did use Quadrajets (spread bore carb). Otherwise they came with Carter carbs which were always square bore carbs.

 

[sherms]

From what I can tell from the casting numbers the intake isn’t original to the motor, Looks like its from a ‘77 400. It’s spread bore so would need to use an adapter to make a square bore carb work. I have a line on a new edelbrock 1411 for pretty decent price thinking that would be a good option?

 

[LouJC]

I would talk to Edelbrock tech support and ask them.
Also some spread bore intakes were made so they would accept either a spread bore or square bore carb. If this one had square bore Thermoquad on it with no adapter that might be the case.

 

[valiant67]

Thermoquad is a spread bore. The factory intake from the 400 is only going to accept a spread bore without an adapter. You also have to watch hood clearance if you add an adapter.

When looking at new carbs, make sure the have Chrysler linkage, both throttle and kick down if an automatic. This can add to the purchase cost.

 

[LouJC]

Yep did some more reading and learned that. Remember the adapter will raise it up 3/4”.

 

[AHBGuru]

You can find rebuilt TQ's online, but you must first determine what you need.

You can probably get away with any non-Lean Burn TQ for a 360, or 400 application - the jetting should be pretty close.

Below is the best TQ guide ever written. I would stick with the '73-'74 model years, to avoid Lean Burn carbs, which do not have ported vacuum for the distributor. 2 carbs from the list, #6321, and #6457, would probably be good choices. Try an ebay search or another good place is National Carburetors (nationalcarburetors.com).
.

A Carter Thermo-Quad Guide (at https://carbkitsource.com/tech/Carter/pages/tqguide-Vaanth.html )

 

[sherms]

Hey guys, thanks so much, really appreciate all the replies. The intake is the same minus a couple months older as the one in the attached pic, I dont think it would support a square bore set up as is. I wrote Edelbrock to get some opinions on adapters with that intake and the 1411, I'll follow up tomorrow and see if there's a better option for carb too. Good point about the linkage totally didn't even think of that, will double check with them about that as well. Wasn't having any luck locating a tq with the same model number, but would a 6000 series and a 9000 series be interchangeable assuming its the same? Also I wonder if a 77 intake and 80 carb were EGR or PPCV, think I gotta go over there and look at the car again. So much stuff to consider

 

[AHBGuru]

Hey guys, thanks so much, really appreciate all the replies. The intake is the same minus a couple months older as the one in the attached pic, I dont think it would support a square bore set up as is. I wrote Edelbrock to get some opinions on adapters with that intake and the 1411, I'll follow up tomorrow and see if there's a better option for carb too. Good point about the linkage totally didn't even think of that, will double check with them about that as well. Wasn't having any luck locating a tq with the same model number, but would a 6000 series and a 9000 series be interchangeable assuming its the same? Also I wonder if a 77 intake and 80 carb were EGR or PPCV, think I gotta go over there and look at the car again. So much stuff to consider

You need to read the link I posted, which identifies what TQ goes with what engine and model year.

I would stay away from all but one aftermarket carb - the Street Demon, which is basically a reengineered TQ. The Eddy's are an ancient design based on the old Carter AFB/AVS carbs, and are a poor choice for a daily driver. Holley 4150/4160 are even worse, although the '71 383 did use a 4160.

Leaner is better. Allow me to reinforce that point:

Leaner is better. Get a reman TQ, using the ID guide, or get a new Street Demon:
.

Demon 1904 750 CFM Street Demon Carburetor (at https://www.holley.com/products/fuel_systems/carburetors/demon/street_demon/parts/1904 )

 

[sherms]

You need to read the link I posted, which identifies what TQ goes with what engine and model year.

I would stay away from all but one aftermarket carb - the Street Demon, which is basically a reengineered TQ. The Eddy's are an ancient design based on the old Carter AFB/AVS carbs, and are a poor choice for a daily driver. Holley 4150/4160 are even worse, although the '71 383 did use a 4160.

Leaner is better. Allow me to reinforce that point:

Leaner is better. Get a reman TQ, using the ID guide, or get a new Street Demon:
.

Demon 1904 750 CFM Street Demon Carburetor (at https://www.holley.com/products/fuel_systems/carburetors/demon/street_demon/parts/1904 )

Thanks Guru, I’ll for sure check out the street demon. That TQ page is where I originally got the info about the carb that’s on there and found out it was meant for a 1980 318. Those 6000 ones you recommended didn’t look to be for a 383 or same year intake I have, so that’s why I was asking if it’s interchangeable. I’ve seen a bunch of positive reviews people using the 1411 with a 383, what would be the issues vs the street demon? Im totally green to these carbs so really appreciate all the replies, feel like I’ve learned a ton from this thread.

 

[AHBGuru]

Thanks Guru, I’ll for sure check out the street demon. That TQ page is where I originally got the info about the carb that’s on there and found out it was meant for a 1980 318. Those 6000 ones you recommended didn’t look to be for a 383 or same year intake I have, so that’s why I was asking if it’s interchangeable. I’ve seen a bunch of positive reviews people using the 1411 with a 383, what would be the issues vs the street demon? Im totally green to these carbs so really appreciate all the replies, feel like I’ve learned a ton from this thread.

The carbs I noted are 400 applications, which would be very close in calibration. The Holley 4160 used on the '71 383, and previous AFB/AVS Carters are all low CFM square-bore carbs, which would require a new intake.

For a street car, the spread-bore TQ and Quadrajet (more on that in a bit) are far more efficient with their smaller primaries, and far better breathing with their huge secondaries. ThermoQuad CFM was 800 for the 1978-1984 318, 1971-1973 340, and 1974-1984 360. CFM was 850 CFM for the 1972-1978 400/440.

I should note that the Street Demon TQ is not actually a spread-bore, but is designed to "act" like one, so it would require either an open-plenum (or modified) spread-bore intake.

Now, another option that would work well is a Quadrajet. Chrysler went with this 750 CFM spread-bore carb in 1985, and it was used in 1985-1989 M body squads, 1985-1987 some 318 trucks/vans, and most1985-1988 (some 1989) 360 trucks/vans.

Cars had 2 basic calibrations, trucks and vans had maybe a dozen.

I've used the Qjet almost exclusively in my squad restorations, with the exception of one R body car. The Qjet is good carb. It's very reliable, easy to rebuild, has very good drivability, and used an integral electric choke. The Qjet holds its "tune" far longer than any TQ or other OEM carb Chrysler had used previously. Parts are still available via AC Delco.

For a 383 in a street application, definitely start with a 360 Qjet, and there are plenty of choices.

In the link below is the Qjet rundown. Generally, the 318 carbs started at 17085407 - 17085417. The 360 carbs started at 17085425. The last 2 in the list (link below) are OEM service numbers for the 1985-1989 318 4bbl squads, so ignore that.

I would suggest a 17085431 or 17087175, which were 360 HD applications.

Carburetor service manuals (at https://www.carbkitsource.com/manuals/cm337.html )

 

[Bearhawke]

You can find rebuilt TQ's online, but you must first determine what you need.

You can probably get away with any non-Lean Burn TQ for a 360, or 400 application - the jetting should be pretty close.

Below is the best TQ guide ever written. I would stick with the '73-'74 model years, to avoid Lean Burn carbs, which do not have ported vacuum for the distributor. 2 carbs from the list, #6321, and #6457, would probably be good choices. Try an ebay search or another good place is National Carburetors (nationalcarburetors.com).
.

A Carter Thermo-Quad Guide (at https://carbkitsource.com/tech/Carter/pages/tqguide-Vaanth.html )

Supposedly; a 1975 TQ that was used on the 360-4V Calif engine would bolt right up and, work on a U code 440. The magical word being 'supposedly'. Many moons ago, I had a gennie 1974 Dodge Monaco x CHP unit, 440 and all. Carb was trashed and, somebody gave me a TQ for a 1975, tossed it on there and, that 440 would actually start and (somewhat) idle, just had adjust the mixture screws out a turn or two so the car would idle properly.

 

[AHBGuru]

Supposedly; a 1975 TQ that was used on the 360-4V Calif engine would bolt right up and, work on a U code 440. The magical word being 'supposedly'. Many moons ago, I had a gennie 1974 Dodge Monaco x CHP unit, 440 and all. Carb was trashed and, somebody gave me a TQ for a 1975, tossed it on there and, that 440 would actually start and (somewhat) idle, just had adjust the mixture screws out a turn or two so the car would idle properly.

Ha, yeah, more than once I've found a factory 850 TQ on 360 and even a couple of 318 squads. Set it and go. I did notice that the Qjet tends to be calibrated a little bit richer than the TQ, and they do run better overall, especially when it's really cold out, as long as the float is set to Chevy 350 specs. The Qjet has the much better integral choke, too (although adjusting that is a PIA).

But the TQ, once tuned up sharp,, is definitely the superior carb - you can tune them really lean on the primary side, and still have more than plenty at WOT, on the secondary side.

The trick these days is finding a good TQ. That's where the Qjet has a slight advantage. GM does a little bit better job making sure parts are stil available. That's not saying a whole lot, however, as they've seemed to fall into the same old trap Chrysler and Ford have, with regard to parts for models over 10 years old.

 

[GLHS60]

Agree with the Chrysler/Dodge linkage Q-jet!!

Chrysler and Ford both used them, not just GM.

Edelbrock carbs are known as the thief of power and happiness.

Thanks
Randy