Best Carb for 340LA 72 Bird

[72RR340LA]

I have a 1972 RoadRunner and I was wondering which carburetor would work best with such a beast of an engine. I'm going to tune the car up but the first step is getting a better carb. Right now it has a Carter Thermoquad, but not a good one. # is 91155 date is 130. I'm going to be running an aluminum intake dual plane and either hooker, hedmen, or flowtech headers. I haven't decided what cam and what lift but that's for another time. If you have any suggestions please let me know, this is my first true project car, and my dream Mopar.

 

[Geoff 2]

You already have the best carb, a Carter TQ. Try & find a 6000 series TQ, less emissions crap.

 

[lemondana]

Find an earlier TQ, get it rebuilt, and use it. that way you don't have to change intakes and it will more than likely, perform better than anything else you might put on it. Just my 2 cents worth.

 

[yella71]

Let the games begin.....My vote is for a Holly.

 

[RJRENTON]

You already have the best carb, a Carter TQ. Try & find a 6000 series TQ, less emissions crap.

The Carter Thermoquad is a great carb....as noted, the 6000 series is a good candidate. Just my opinion of course. You'll get recommendations on the Edelbrock (aka "Eddy") AVS series, a bastardization of the TQ's secondary air valve operating principles....so why not CONSIDER the origional carb?.....unless all your "buddies" are using brand "H" or brand "E" and you don't want to be chastised.....(how horrible).....
BOB RENTON
BOB RENTON

 

[WileERobby]

You already have the best carb, a Carter TQ. Try & find a 6000 series TQ, less emissions crap.

Find an earlier TQ, get it rebuilt, and use it. that way you don't have to change intakes and it will more than likely, perform better than anything else you might put on it. Just my 2 cents worth.

The Carter Thermoquad is a great carb....as noted, the 6000 series is a good candidate. Just my opinion of course. You'll get recommendations on the Edelbrock (aka "Eddy") AVS series, a bastardization of the TQ's secondary air valve operating principles....so why not CONSIDER the origional carb?.....unless all your "buddies" are using brand "H" or brand "E" and you don't want to be chastised.....(how horrible).....
BOB RENTON
BOB RENTON

What they said. Period.

 

[72RR340LA]

What is a good price for a 6000 series? And where should I search?

 

[RemCharger]

The Carter Thermoquad is a great carb....as noted, the 6000 series is a good candidate. Just my opinion of course. You'll get recommendations on the Edelbrock (aka "Eddy") AVS series, a bastardization of the TQ's secondary air valve operating principles....so why not CONSIDER the origional carb?.....unless all your "buddies" are using brand "H" or brand "E" and you don't want to be chastised.....(how horrible).....
BOB RENTON
BOB RENTON

The Carter AVS came out before the thermobog, so it's hard to say what was a bastardization of what.
Can the t-quad work? Of course they can, many a superstocker has proven it.
However for a first timer, they can be an obstinate carb to get working properly. Part of the reason holleys became the single most widely used carb for performance applications. Ease of tuning, and maximum performance.
Some facts, some opinions.

 

[72RR340LA]

and is an 850 (one off of a 440/400) too big for 340?

 

[72RR340LA]

also is there a way to buy the center piece that is made of plastic or a way to get an aluminum one?

 

[RJRENTON]

The Carter AVS came out before the thermobog, so it's hard to say what was a bastardization of what.
Can the t-quad work? Of course they can, many a superstocker has proven it.
However for a first timer, they can be an obstinate carb to get working properly. Part of the reason holleys became the single most widely used carb for performance applications. Ease of tuning, and maximum performance.
Some facts, some opinions.

The Carter AVS and later the Thermoquad carbs as origional equipment had a few shortcomings. But, can be "corrected" by learning, first hand, how they work, rather than taking someone elses word about their operation. Armed with the knowledge of the hows and whys of TQ operation the "first timer" will know how to proceed based on the origional complaint. Usually, first issue is a secondary "bog" or stumble or flat spot on W.O.T acceleration, due, largely to someone's influence saying loosen the air valve tension spring....then trying to recover from that error. The error being not tightening the air valve tension spring preload slightly.
To replace the TQ with brand H or E, without changing the manifold and using an adaptor plate, usually results poor performance and the resulting stigma that the TQ carbs are "no good" or are a POS.
We learn by doing and tuning a TQ carb is easy once its operation and its shortcomings are known. Just my opinion of course.
BOB RENTON

 

[RJRENTON]

and is an 850 (one off of a 440/400) too big for 340?

Some will say no...it'll be ok....others will disagree. The TQ has small primary throttle plates and booster venturii assemblies which results in high mixture velocities and crisp throttle response. Too large of a carb combined with a low numeric rear gear ratio, a standard cam, and a heavy car will usually result in poor performance although a 340 engine, a moderate rear gear ratio and an A body may be ok, but only actual 1/4 mile time slips comparing the two combinations is the true determination of which combination is better not speculation.

BTW....I'm not aware that anyone makes an aluminum or zinc replacement for the phenolic fuel bowl for the TC carb.
BOB RENTON

 

[72RR340LA]

Some will say no...it'll be ok....others will disagree. The TQ has small primary throttle plates and booster venturii assemblies which redults in high mixture velocities and crisp throttle response. Too large of a carb combined with a low numeric rear gear ratio, a standard cam, and a heavy car will usually redult in poor performance although a 340 engine, a moderate rear gear ratio and an A body may be ok, but only actual 1/4 mile time slips comparing the two combinations is the true determination of which combination is bettrt not speculation.

BTW....I'm not aware that anyone makes an aluminum or zinc replacement for the phenolic fuel bowl for the TC carb.
BOB RENTON

i have a 8 3/4 rear end 1972 roadrunner. its a b body not a body.

 

[RJRENTON]

i have a 8 3/4 rear end 1972 roadrunner. its a b body not a body.

My reference was not to your car...but to a lighter weight A body could probably use the bigger or higher flow rate TQ. You note your car has a 8-3/4" rear gear but what is the ratio?? Likely its either 2.94 or 3.23....both would benefit from the smaller TQ carb.
BOB RENTON

 

[Photon440]

and is an 850 (one off of a 440/400) too big for 340?

There isn't a great deal of difference - the 'big' carb with the 1 1/2 primaries flows 6% more air than the 'little' carb. Considering that the factory used the 800 cfm 'little' carb on 318 police cars in the 1980s I'd be confident that the 340 could handle the extra 50 cfm.

 

[72RR340LA]

My reference was not to your car...but to a lighter weight A body could probably use the bigger or higher flow rate TQ. You note your car has a 8-3/4" rear gear but what is the ratio?? Likely its either 2.94 or 3.23....both would benefit from the smaller TQ carb.
BOB RENTON

how to find out what gears my rear end has?

 

[72RR340LA]

There isn't a great deal of difference - the 'big' carb with the 1 1/2 primaries flows 6% more air than the 'little' carb. Considering that the factory used the 800 cfm 'little' carb on 318 police cars in the 1980s I'd be confident that the 340 could handle the extra 50 cfm.

okay got it. I know that earlier the year the better but I'm having a hard time finding any.

 

[Geoff 2]

72RR,
[1] The TQ is your best bet. Use brand H [ & clones ] as door stops.
There are plenty of 6000 series carbs on ebay. Get one & get a rebuild kit. Good to go. You could also contact Woodruff carbs, a sponsor on this forum
[2] 800 or 850 cfm version [ 1 3/8" v 1 1/2" ] pri t/bores. I would say if the engine is going to be low/medium performance, use the 800. If higher perf is intended, then the 850. Bottom line: there isn't much difference, but I would go for the 800. 302 & 351 Ferds here came with 800 TQs.
[3] Many ignorant people think the plastic centre was for cost reduction. It wasn't, it was to keep the fuel 20* cooler to reduce percolation & evaporation loss. It is a plus!
[4] I have installed Mopar TQs to many non-Mopar engines. Some of the boys went on a country trip about 3 weeks back. Some cars had brand H crap. Starting out, they all filled up close to home & then topped up along the way. The TQ cars, one of which was a 455 Pontiac, took 22 litres, H cars took 35 litres....

 

[Geoff 2]

72RR,
I see TQs on ebay quoting the number 2146. That is the casting # for the air horn. You need to know the model # which is stamped on one the mounting feet. You could also try www.thecarburetorshop.com. I understand he is selling off stuff & retiring.

 

[RJRENTON]

how to find out what gears my rear end has?

To determine the rear gear ratio (approximately), raise the rear of the car, so both wheels sre off the ground. Then, mark the drive shaft. Then rotate a rear wheel one revolution (assuming that your vehicle has Mopar's SURE GRIP so the opposite wheel rotates in the same direction), count the number of times the DRIVE SHAFT rotates. This is an APPROXIMATE of the rear gear ratio. The higher the ratio number, the more torque is developed by the engine and the easier to accelerate the vehicle. Just my opinion of course.
BOB RENTON