650CFM Eddies seems to be fine for 340's (see below)
The Great Carter Thermoquad Numbers Decode List
Here are the Carter TQ number that I was able to lift from Govier's
interchange book. The numbers go from 1971 to 1974.
The letters listed under Models refer to carline (First letter of VIN)
Number Year Engine Trans Remarks Models
=======================================================================
4972S 1971 340 Manl VLBJRW
4973S 1971 340 Auto VLBJRW
6090S 1972 400 Auto RWPD
6138S 1972 340 Manl VLBJRW
6139S 1972 340 Auto VLBJRW
6140S 1972 400 Manl HP RW
6165S 1972 400 Manl HP w/air pump RW
6166S 1972 400 Auto HP w/air pump RW
6212S 340 MARINE
6318S 1973 340 Manl VLBJRW
6319S 1973 340 Auto VLBJRW
6320S 1973 400 Manl HP RW
6321S 1973 400 Auto HP RWPD
6322S 1973 440 Auto LP PDCY
6324S 1973 440 Manl HP RWPDC
6339S 1973 340 Manl w/N98 VLBJRW
6340S 1973 340 Auto w/N98 VLBJRW
6341S 1973 400 Manl HP w/N98 RW
6342S 1973 400 Auto HP w/N95-N98 RWPD
6394S 1972 340 Auto Export L
6410S 1973 440 Auto LP w/N98 PDCY
6411S 1973 440 Auto HP w/N95-N98 RWPDC
6452S 1974 360 Manl HP VLBJRW
6453S 1974 360 Auto HP VLBJRW
6454S 1974 360 Manl HP Calif VLBJRW
6455S 1974 360 Auto HP Calif VLBJRW
6456S 1974 400 Manl HP RW
6460S 1974 440 Auto LP Early PDCY
6461S 1974 440 Auto LP Calif Early PDCY
6462S 1974 440 Auto HP Early RWPDC
6463S 1974 440 Auto HP Calif Early RWPDC
6488S 1974 360 Auto RWPDC
6489S 1974 400 Auto HP Early RWPDC
6503S 1974 400 Auto HP Export W
9000S 1974 318 Both Export D
9013S 1974 360 Auto Late RW
9014S 1974 400 Auto HP Late RWPDC
9015S 1974 440 Auto HP Late RWPDC
9016S 1974 440 Auto HP Calif Late RWPDC
9023S 1974 440 Auto LP Late PDCY
9024S 1974 440 Auto LP Calif Late PDCY
9801S 1974 383 Auto Perf & Off road 800 CFM
There always seems to be some confusion around here about TQ's and their
cfm ratings, etc, and I found a response to someone's question in the
'Performance Clinic' column by Dick Landy in the Aug/Sept 94 issue of Mopar
Muscle (page 9). It reads...
[font=Verdana]"There are two basic ThermoQuad Carburetors: one with 1 3/8" primaries and 2
1/4" secondaries for the 318 and 340 (A) engines and a Holley comparison CFM
of 650 CFM.[/font] The second one had 1 1/2" primaries and 2 1/4" secondaries with
a Holley comparison CFM of 820. It's used with some 360s and all the 'B'
engines. Actually, Carter called this one a 1000 CFM unit. Their airflow
numbers were measured differently than Holley. Also, some ThermoQuads had
the secondary air-door limited, which also decreased the CFM."