Thermoquad question

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we run a T.Q. on our 340 stocker. we use a oxy sensor in header collector to see a/f mixture. easy way to tune the carb. when we tried that, had a a/f mixture of 12.3 to 12.4 all way down the track, this was with a clutch car. that makes it a flat fuel curve. main thing done to carb, was get rid of the inlet piece. and tap carb for 3/8 pipe thread , adds volume of fuel to carb. i used brass nipple.
 
Babyblue66 said:
Not all of them are great carbs. I've found the 72 to 74 are the best. There are some later non-leanburn versions out there too. Many years ago I tried running a later 400 carb on my 360 fury. It was lean and just didn't make the power. I swapped to a 73 440 thermoquad and the difference was substantial. I think they're great but the plastic bodies are going bad on most of mine. They're just getting old.
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The 71-74 TQ are the best to use, Truck TQ were affected later as the emission requirements came in later for them. Some TQ do not even have ported vacuum for the distributor vacuum advance. They do require a choke to start or they will drive you crazy.
 
66fs said:
The 71-74 TQ are the best to use, Truck TQ were affected later as the emission requirements came in later for them. Some TQ do not even have ported vacuum for the distributor vacuum advance. They do require a choke to start or they will drive you crazy.
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71 is press in jets, avoid unless you need to be date correct.
The electric choke helper in 73 and up helps it work better, because the choke needs to be pretty close to fully closed for them to start quickly.
 
G70464 said:
71 is press in jets, avoid unless you need to be date correct.
The electric choke helper in 73 and up helps it work better, because the choke needs to be pretty close to fully closed for them to start quickly.
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I know, I have a 71 340 4 speed TQ and love it. Runs like the car was fuel injected, but it took a bit of trial and error with the choke and pull off.
 
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That’s a carb for ya. Keep tweaking until it great.
 
The secondary air valve choke/pull off, whatever you want to call it, can cause some strange problems. Especially as these carbs age & the rubber diaphragm goes hard from age & heat.
Usual symptom is like stutter when the secondaries start to open. What happens is the AV releases too slowly, AV acts like a choke & the mixture goes very rich.
Fix is very simple; buy a new AV & if at all in doubt, replace it.
 
Bewy said:
The secondary air valve choke/pull off, whatever you want to call it, can cause some strange problems. Especially as these carbs age & the rubber diaphragm goes hard from age & heat.
Usual symptom is like stutter when the secondaries start to open. What happens is the AV releases too slowly, AV acts like a choke & the mixture goes very rich.
Fix is very simple; buy a new AV & if at all in doubt, replace it.
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It is what really keeps it from bogging more than the spring tension.
Learned early on to have it pull the door tight just with moderate spring tension.
 
That’s true. Everyone wants to run it loose as heck.
 
perfacar said:
we run a T.Q. on our 340 stocker. we use a oxy sensor in header collector to see a/f mixture. easy way to tune the carb. when we tried that, had a a/f mixture of 12.3 to 12.4 all way down the track, this was with a clutch car. that makes it a flat fuel curve. main thing done to carb, was get rid of the inlet piece. and tap carb for 3/8 pipe thread , adds volume of fuel to carb. i used brass nipple.
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Well heck, why didn't I think of that... I have been fighting a losing battle trying to get enough fuel in the carb. Wouldn't happen to have a picture would you?
 
Hysteric said:
Except the best part sadly.
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Hence the edit to my original post: :D
- "One of my fondest childhood memories is my dad gunning the old Ramcharger whenever he needed to pass cars. That roar that thermoquad emitted was unique, no other carb did that. Not even the new Street Demons, I mean they do slightly, they're just too... "tame""
 
The info in post #35 is misleading. The Aussie Ford carbs had very lean sec jets, fixed in 5 min with a numbered drill set. They will run just as well as Mopar TQs. The Superquad was a universal carb & was made in TQs & AFBs.
 
Dan the man said:
To hard to get parts for, by the time that you would find everything you need for one the season is over with.
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Don't really need much parts. Carters never needed all the extra parts to make them run good. The best part is you don't "need" a bunch of tuning parts so you can sell them and have less stuff taking up space. You also have a better running carb that you don't have to mess with for the rest of your life.
 
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I ran across an add for 8 thermoquads but the guy wants $500 for all of them. I could do something like that if others want to purchase some of the TQ's. Here is the list:
6321S 73 400 Automatic
6324S 73 440 HP Automatic
6457S 74 400 HP Automatic
9011S 75 440 HP Automatic
9050S 75 400 Automatic
9140S 78 400 Automatic
9196S 79 360 Automatic x 2 One incomplete
9256S 79 318 Automatic
Reply or PM me if interested in any of these. If enough interest, I will get them (60 miles away) and send them to you. I would need $70/carb or so to make this work as there will be some that no one wants. Shipping extra, but about $20/carb.
Bob
 
I pulled one off an E58 360 engine in a cop
Car. Rebuilt it, put it on a. 350 SBC, holley street dominator intake 442/465 lift cam.
Ran like a scalded dog !
It is by far the best street carb I ever had
 
had one off a 440 on my 318 DART GREAT CARB IF YOU CAN FIND A GOOD ONE
 
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