Carb recommendations / fit

[jebirr]

Just bought 72 340 Cuda. Previous owner put undersized manual choke Edelbrock AVS carb. DIdn't hook up the choke. Add on chock kinda pricey so thinking about just swapping whole carb out.

Is anyone running a Demon with stock intake and especially stock air cleaner? Want to stick with stock air cleaner and intake. Considering just getting a larger AVS with electric choke (which I know air cleaner will fit) but Demon looks attractive as well.

Thanks

 

[540HemiCuda]

Are you referring to the 'Street Demon'? That is my go-to carb for stock to near stock combos. I have installed several. They have electric chokes standard and can interfere with the air cleaner on some applications.

 

[jebirr]

Are you referring to the 'Street Demon'? That is my go-to carb for stock to near stock combos. I have installed several. They have electric chokes standard and can interfere with the air cleaner on some applications.

Yes - Street Demon. Really want to maintain stock air cleaner and am concerned about interference with - thus the post. Makes me wonder if Edelbrock with electric choke would interfere too as mine doesn't have choke on it.

 

[bennydodge]

Yes - Street Demon. Really want to maintain stock air cleaner and am concerned about interference with - thus the post. Makes me wonder if Edelbrock with electric choke would interfere too as mine doesn't have choke on it.

Yes, the stock single snorkel 340 air cleaner will work. I've ran this setup for many years with no issues.

 

[Chryco Psycho]

My Fav carb is the Profom , might want to check those out .
If you are just using the car in warm weather you should be fine without choke .

 

[Xcudame]

Street Demon will work. But a 72 came with a Thermoquad from the factory and are so awesome when those huge secondaries open up!! Thermoquads are easy to rebuild, even if the throttle blade shafts have to be re-bushed (biggest issue with some used ones).

 

[540HemiCuda]

Thermoquads were good carbs. But the new Street Demons have all of the Thermoquad's features and a few more, PLUS the new Street Demons do not have a gasket under the fuel. The Thermoquads have ALWAYS been prone to leaks under the fuel bowl because of that. Even back then.

I NEVER recommend Thermoquads anymore. The bowls can warp and not be able to be sealed. The throttle shafts can be rebushed, but why go to that trouble when a better, new unit is available for probably less money when it's all said and done. And finally, there are realistically no rods and jets available for them anymore. And they were jetted for very different fuel than they are delivering today.

Try a Street Demon and you will see why I don't use the CarterBrocks anymore. Or the Thermoquads. The new Street Demons are THE carb for milder combos today.......bar none.

Now, if you have a bumpy idle, the 4150 Holley platform (though not necessarily Holley anymore given their problems) is a better choice for those applications.

The only problem I have seen with the Street Demons is that the electric choke sits high enough on the carb that it can hit the air cleaner. But a spacer between the carb and the air cleaner (IF there is enough room under the hood and there usually is) will remedy that.

 

[66fs]

I still run a TQ whenever possible and have never had any problems. Nice to hear the Street Demons are as good as they looked. Nice to have a new carb available that is an all around performer as the TQ.

 

[Xcudame]

I love the Thermoquad and I like the Holley Street Demon. The Demon is missing one important feature of the Thermoquad that makes me love the TQ so much - those huge secondaries that sound so freaking awesome when you squeeze down on the go pedal!

When rebuilding a TQ, some have forgotten to replace the two square cross sectioned O-rings under the primary jets and that has given them an undeserved bad reputation.

 

[540HemiCuda]

Warped middle bodies that leak fuel has given Thermoquads a black eye since they were new. Now, the limited availability of good ones, the lack of tuning parts, and better alternatives has killed them for everyone but a few die hards and picky restoration guys. Most buyers nowadays need a carb that works right out of the box. That is not any 50+ year old used carb. Even one that has been 'rebuilt'. And is not something that I would recommend to guys who are not fairly fluent in carbs.

Now, if someone is that hooked on the sound, they can always get a Quadrajunk.......I mean Quadrajet. They are still available new.

.

 

[Ricks72Chlgr440]

Now, if someone is that hooked on the sound, they can always get a Quadrajunk.......I mean Quadrajet. They are still available new.

.

That comment borders on blasphemy! Yeah, yeah I know Ma Mopar put those QJ's on some vehicles (i.e. trucks) in the 80's. They were cheap so likely that's why. Ugh.

 

[66fs]

Warped middle bodies that leak fuel has given Thermoquads a black eye since they were new. Now, the limited availability of good ones, the lack of tuning parts, and better alternatives has killed them for everyone but a few die hards and picky restoration guys. Most buyers nowadays need a carb that works right out of the box. That is not any 50+ year old used carb. Even one that has been 'rebuilt'. And is not something that I would recommend to guys who are not fairly fluent in carbs.

Now, if someone is that hooked on the sound, they can always get a Quadrajunk.......I mean Quadrajet. They are still available new.

.

Funny, I've never had any of those "problems" and never needed to recalibrate the jets or rods. They aren't Holleys. The hard part is finding a good HP core. As for a QJet, they are second behind a TQ for best street carb, but they take more work to get them there.

 

[540HemiCuda]

If you are saying that any carb that was calibrated and tuned for 1970s gasoline is still as good for today's very, very different gasoline, I just have to disagree and have a question; How many Thermoquads have you tuned for today's gasoline with a wide band? Given the extremely limited availability of tuning parts, I can guess the answer. And most driving is done on the transitions anyway. Give us a quick detail on how to dial in those transitions. Hint: it takes drill bits.


EVERY original stock muscle car engine I have worked on can benefit from better timing curves and carb calibrations. EVERY ONE. That was true in 1975 and is even more true today. Preferring to run those old carbs untuned for today's realities is tantamount to preferring to run point ignitions over electronic ignitions. Will they run the car........yes they will. Are there better choices now......yes there are. The final choice comes down to what the owner's priorities and abilities are.

And I will make two more points; First, the Thermoquad was introduced in the first place to deal with emission issues, not necessarily to be the best carb for performance. And second, the ONLY high performance engine it was used on was the 340. Mopar even experimented with 6 barrels on the Hemi to deal with the changing emissions environment, but I have never read anything about Mopar experimenting with the Thermoquad for that application. Have you? I wonder WHY that was? Or why, with the huge flow capabilities of the Thermoquads did Mopar not experiment with replacing the triple Holleys on the 440 with one?

I have nothing against the AFBs, AVSs, or the Thermoquads. They have their place in our history. But using them today for most guys, makes as much sense as using early 70s blends of oils and saying they have had no trouble doing it. But just because a half century old product hasn't totally failed you, does not mean that there aren't simply better choices for us today.

There is absolutely nothing wrong with someone preferring to run a Thermoquad on their own ride for whatever reason. But generally recommending them to others is a completely different thing and should not be done in most instances.

.

 

[66fs]

I've run a ThermoQuad on 273's, 318's, 340's and 383 street cars. I don't need a wide band to tune an engine, been doing it for at least 50 years. The ThermoQuad was a staple of Stock and Super Stock racers since they came out, not that Drag Racing is anything I'd waste my time on. I wouldn't have a Holley on any street car, let alone 3 of them. I love working on cars, but I hate having to work on them. If buying a new carb, I'd look at a Street Demon or AVS II. I would even consider a Quadra-Jet, but I would not run one out of the box. New means nothing to me and I have rarely seen anything new be better or last longer than the old stuff, including racing oil.

 

[Ricks72Chlgr440]

If you are saying that any carb that was calibrated and tuned for 1970s gasoline is still as good for today's very, very different gasoline, I just have to disagree and have a question; How many Thermoquads have you tuned for today's gasoline with a wide band? Given the extremely limited availability of tuning parts, I can guess the answer. And most driving is done on the transitions anyway. Give us a quick detail on how to dial in those transitions. Hint: it takes drill bits.


EVERY original stock muscle car engine I have worked on can benefit from better timing curves and carb calibrations. EVERY ONE. That was true in 1975 and is even more true today. Preferring to run those old carbs untuned for today's realities is tantamount to preferring to run point ignitions over electronic ignitions. Will they run the car........yes they will. Are there better choices now......yes there are. The final choice comes down to what the owner's priorities and abilities are.

And I will make two more points; First, the Thermoquad was introduced in the first place to deal with emission issues, not necessarily to be the best carb for performance. And second, the ONLY high performance engine it was used on was the 340. Mopar even experimented with 6 barrels on the Hemi to deal with the changing emissions environment, but I have never read anything about Mopar experimenting with the Thermoquad for that application. Have you? I wonder WHY that was? Or why, with the huge flow capabilities of the Thermoquads did Mopar not experiment with replacing the triple Holleys on the 440 with one?

I have nothing against the AFBs, AVSs, or the Thermoquads. They have their place in our history. But using them today for most guys, makes as much sense as using early 70s blends of oils and saying they have had no trouble doing it. But just because a half century old product hasn't totally failed you, does not mean that there aren't simply better choices for us today.

There is absolutely nothing wrong with someone preferring to run a Thermoquad on their own ride for whatever reason. But generally recommending them to others is a completely different thing and should not be done in most instances.

.

Amen, well said.

 

[Xcudame]

I guess I'm just lucky because I have around 40 Thermoquads, huge selection of needles, and was taught to super tune them buy the man who tuned California Highway Patrol cars back in the 70s and 80s. Of the 40 or so plastic bodies I have, only one was warped and a few minutes on an old camshaft grinding stone (very flat), fixed that no problem.

The beauty of the TQ is you can tune one for a 318 and pop it on a 440 and it will run. Maybe a slight adjustment of the mixture screws. And the opposite is true as well, 440 to 318.