Re: Factory 340 carbs
[Re: 70duster340]
#992328
05/14/11 06:20 PM
05/14/11 06:20 PM
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Joined: Feb 2003
Posts: 8,020 Pangaea
B5 Bee
master
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master
Joined: Feb 2003
Posts: 8,020
Pangaea
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2300 Holleys - 1350/970cfm Carter Thermoquad - 800cfm Carter AVS - 625cfm Carter AFB - 625cfm
Last edited by B5 Bee; 05/14/11 06:23 PM.
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Re: Factory 340 carbs
[Re: 70duster340]
#992331
05/14/11 06:48 PM
05/14/11 06:48 PM
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Joined: Jan 2003
Posts: 27,451 So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,451
So Cal
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Quote:
So, was the thermoquad on the later model 340's? What year for each version of carb, if that is possible? Also, what cfm rating was used?
Thanks for all the replies!!!
68-70 AVS - 625 cfm 70 340-6 2300 Holleys - 1350/970cfm 71-73 Thermoquad - 800 cfm
No AFB's on 340's.
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Re: Factory 340 carbs
[Re: autoxcuda]
#992333
05/14/11 06:58 PM
05/14/11 06:58 PM
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Joined: Feb 2003
Posts: 8,020 Pangaea
B5 Bee
master
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master
Joined: Feb 2003
Posts: 8,020
Pangaea
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Quote:
Quote:
So, was the thermoquad on the later model 340's? What year for each version of carb, if that is possible? Also, what cfm rating was used?
Thanks for all the replies!!!
68-70 AVS - 625 cfm 70 340-6 2300 Holleys - 1350/970cfm 71-73 Thermoquad - 800 cfm
No AFB's on 340's.
Sure there was, just not automotive. That's an AFB under the flame arrestor on this '73 340.
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Re: Factory 340 carbs
[Re: B5 Bee]
#992334
05/14/11 07:07 PM
05/14/11 07:07 PM
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Joined: Jan 2003
Posts: 27,451 So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,451
So Cal
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Quote:
Quote:
Quote:
So, was the thermoquad on the later model 340's? What year for each version of carb, if that is possible? Also, what cfm rating was used?
Thanks for all the replies!!!
68-70 AVS - 625 cfm 70 340-6 2300 Holleys - 1350/970cfm 71-73 Thermoquad - 800 cfm
No AFB's on 340's.
Sure there was, just not automotive. That's an AFB under the flame arrestor on this '73 340.
..
We was looking for a automotive application. But industrial, boat, etc have all kinds of different stuff.
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Re: Factory 340 carbs
[Re: 70duster340]
#992336
05/14/11 07:20 PM
05/14/11 07:20 PM
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Joined: Jan 2003
Posts: 826 Stone Mt, GA.
DEMONSIZZLER
super gas
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super gas
Joined: Jan 2003
Posts: 826
Stone Mt, GA.
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The ThermoQuad was introduced in '71 for the 1st time as on oem carb with 800 cfm's. It had existed since '69 as an after-market performance carb avail in either 850 cfm's or 1,000 cfms and is know as the Competition Series.
The primaries on the '71-'73 340 T.Q.'s was approx 232 cfm's and a whopping 570 cfm's on the 2ndary side. The double booster design of the primaries gives the T.Q. an excellent port floor signal and exceptional fuel/air atomization. And the sophisticated metering system is very precise. And the carb was very 'change-able' to increasing EPA demands for cleaner running engines so it was easy to add smogger settings and parts that made the carb pass increasing emissions requirements.
The '71 340 T.Q. was a one year only design, derived from the 69 Competition Series carb. The carb is an air metered carb while all '72-up ThermoQuads are solid fuel metered.
CS series 850.......4846S for press in jets, ....................4846SA for screw in jets, CS series 1,000.....4847S for press in jets, ....................4847SA for screw in jets, '71 340 800.........4972 for 4 spd, ....................4973 for automatic, '72 340 800.........6138 for 4 spd, ....................6139 for auto, '73 340 800.........6318 for 4 spd, ....................6319 for auto.
These '72 carbs(oem)will suffer in performance if the correct casting # top is not used. The best 340 T.Q. is the '72 as it had the best metering system and it will make very close to the same power as the early '72-'73 big block 850 cfm carbs.
Over-all, these carbs are hard to beat in both gas mileage and performance!
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Re: Factory 340 carbs
[Re: B5 Bee]
#992337
05/14/11 07:26 PM
05/14/11 07:26 PM
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Joined: Jan 2003
Posts: 27,451 So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,451
So Cal
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Quote:
Well, the question was ALL the carbs that came on factory 340s.
That's true.
But without saying what the AFB's were on, some people reading it will think they came on 68-73 automotive applications and it will just confuse them.
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Re: Factory 340 carbs
[Re: 70duster340]
#992340
05/15/11 11:31 PM
05/15/11 11:31 PM
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Joined: Jan 2003
Posts: 42,714 Spokane Washington
ScottSmith_Harms
Mr Wizzard
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Mr Wizzard
Joined: Jan 2003
Posts: 42,714
Spokane Washington
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Quote:
Don't mean to seem ignorant, but what is the difference between the AFB and the AVS?
Well assuming you are trying identify one or the other and not every single detail of what set's them appart?
These are AFB's (Aluminum Four Barrel)
There were two basic designs on Mopars, early and late. These are the early styles (with vestigial choke tube in the lid) found on early to mid 60's Mopars.
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Re: Factory 340 carbs
[Re: 70duster340]
#992345
05/16/11 12:17 AM
05/16/11 12:17 AM
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Joined: May 2011
Posts: 2 Woodburn, IN USA
Richard Reardon
member
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member
Joined: May 2011
Posts: 2
Woodburn, IN USA
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Hi Robert, What came first? It was the Carter AFB, alias "Aluminum Four Barrel" These were around in the 1950s and beyond. The secondaries are activated when the secondary counter weights are overcome by the air requirement of the engine, hence the secondaries kick in, kinda an on a demand scenario as required by the engine. These counter weights can be viewed by looking to the outside corners of the carb while looking inside the secondary oriface. The AVS is also a Carter 4-bbl, but the secondaries have a secondary "flapper" like another choke plate. AVS stands for Air Valve Secondary. The flapper also works on engine air demand and is controlled by a spring that is seen on the flapper and it's adjusted at the factory to come in on demand of that particular engine, once the air requirement over comes the tension on the spring. Caution -- If you decide to change the tension, BE SURE YOU DON'T LET THE SPRING FLY!> Make sure you count the turns so you can get back to that setting, if you need to, or you'll have a heck of a time resetting the thing. You can "tune" it to have the scondaries come in earlier or later by changing the spring turns/tension. This is a real nice touch on this carb. Most early AFBs were low on cfm, like 400 - 485cfm. Some went to 500 to 600-625cfm and later on to higher cfm ratings. You can get 'em now in the Edlebrock form up to 750cfm. Years ago, Vic Edlebrock bought the rights for Carter/Federal/Mogul, so he could continue the production of these carbs. I think the AVS on my 1970 340 Duster was rated at either 615 or 650cfm. At any rate the 1971 Carter Thermoquad rated at 800cfm, had it all over that little AVS. However, these Thermoquads had leakage problems (cracks) with that phenolic bowl fuel center section and I don't think much of them. The AVS off a 440 is the hot ticket, especially for a 383/400 and larger MOPAR engines that used smaller carbs. The 440 AVS is rated at 750 cfm. But it is jetted and metered for a big block and would require mods to be used on a 340 though, but this is a good carb to use if you're looking for more CFM. I hope this helps you understand these carbs a bit better. You may contact me at mrreardon2@aol.com if you need to ask more questions. I'll try to help you. Richard413 (A new member to the MOPARTS website)
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Re: Factory 340 carbs
[Re: Richard Reardon]
#992346
05/16/11 12:22 AM
05/16/11 12:22 AM
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Joined: Jan 2003
Posts: 42,714 Spokane Washington
ScottSmith_Harms
Mr Wizzard
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Mr Wizzard
Joined: Jan 2003
Posts: 42,714
Spokane Washington
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Quote:
However, these Thermoquads had leakage problems (cracks) with that phenolic bowl fuel center section and I don't think much of them.
I respectfully dissagree with this statement. "Rumored" to have had crack problems would be a lot more accurate.
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