71 vs 72 thermoquad

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Demonizer71

Demonizer71

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What's the Difference? Plus will a 72 work on a 71 intake? I've read that the 71 Tquad had smaller primaries for emissions etc.
 
Demonator72 said:
What's the Difference? Plus will a 72 work on a 71 intake? I've read that the 71 Tquad had smaller primaries for emissions etc.
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The only difference between the two that I'm aware of is that the 72 has EGR and ported-spark vacuum connections. Later models had electric chokes, but I'm not sure when they were introduced on production Mopars. Venturi size on early and late models is the same. There's no reason why a 72 carb would not work on a 71 manifold as long as the un-used emission ports were properly capped.
 
72 Demon said:
The only difference between the two that I'm aware of is that the 72 has EGR and ported-spark vacuum connections. Later models had electric chokes, but I'm not sure when they were introduced on production Mopars. Venturi size on early and late models is the same. There's no reason why a 72 carb would not work on a 71 manifold as long as the un-used emission ports were properly capped.
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I think this needs clarification. The large/small primaries were not year specific. They made both sizes pretty much throughout the '70s/early 80s.
 
hi, the carbs will work as both use same intake manifold. the difference is in the secondary jet. the 71 sec jets were shorter as the body had longer casting to put jet near the floor. the72 and up, has a longer sec jet, commanly refered to as a solid fuel type.the casting was shortened to make then fit. both have 1 3/8 primary throttle bores. the 340 used the 1 3/8 bores. 71 through 73 . the intake 2100 has no EGR fittings in floor.
 
GTXperience said:
Air-metering vs fuel-metering. A lot of people like to go with the '72 & up for this reason.
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that is the big difference....agree...alot of people use the 72 and newer air metering thermoquad.

unless you are doing a restoration...i would use the 72+....

last weekend at MATS, a friend has a 71 demon D/SA that was running a 72 and newer thermoquad...
 
Just to 'clarify' a few facts on the subject. The differences are:

The '71 340 carb was 'based' on the Competition Series 850 cfm T.Q. and
as stated above, the '71 T.Q. was:
a)air metered..................'72 model was fuel metered;
b)both the '71 340 and the '72 340 carb was rated @800 cfm's;
c)'71 jets, bowl, base and top are NOT interchangeable with the '72 carb/parts;
d)'71 340 had the idle mix screws 'angled' away from the centerline of the carb while the '72-'84 oem carbs had the idle mix screws 'angling' upward;
e)the '71 340 carb had the front vent stack as an integral part of the top casting while the '72 carb had a push-in cylindrical steel vent stack;
These are the most noticeable side-by-side differences between the two carbs. An the '71 carbs are worth more $$$ because of the 'rarity' of the '71 model.

The '72 is the better performer of the two because it has more sophisticated metering systems. The '71 carb is easier to pull trash into the metering system while the '72 has the cronic problem of leaky main jet wells on the underside of the bowl.

In my opinion, the '72 340 carb is the best performing 800 cfm T.Q., David

'71 340 T.Q. pic:

DSCN1531.JPG
 
What is the difference between air and fuel metering, as in how do they work?
 
Hey Demon Sizzler...got a TQ off a '72 D250 w/ a 360 under the hood. Truck had about 70k on the odo, was in a wreck that wiped out the driver's side. Picked up the carb for $30 and was planning on using it on my budget-built 340. Can I pick your brain on this thread (don't want to high-jack) and spread abit 'o knowledge-I know you are the TQ guru.
 
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