Carb too small?

[blueduster340]

Would a 600 cfm Edelbrock or Holley Carb we too small on a 340?

The 340 will have an rpm air gap
hooker headers
comp cams xtreme energy 274H
3.91 gears
pretty much a hopped up performance street car that I would race once or twice a year.
rpm range should be from 1800-6000

I know they came stock with 800 cfm thermoquads but I'll probably go with an aftermarket carb. Also looking for recommendations on what carb I should run on my engine.

[rumblefish360]

Yes and no. The smaller carb would be giving you great throttle response. You would be giving up HP on top.
A T-Q will not fit and a adapter will probably cause interfearance with the hood. A carb of 650 -750 will do fine.
Now here the trick. If your going to see wide open throttle (WOT) often, go 750. For around town, it could be a pain to tune in nice and get a nice throttle response.
If your into cruising around more so, a 650 is it.
Since track time will be low for you, the 650 or 700 cfm will do nice.
If the carb you chose is a Holley, I'd do a 700.
A Demon would be a 650. (They flow a little better than rated So I heard and read) Ethier carb would be a good choice.
If you like the Carter style carbs, I would do a large AVS and not an AFB myself.
In a pinch or just for a something to cruise around in, a 600 will work.

[Hobbes]

You'll probably get a bunch of people giving you the same advice, but the Thermoquad is an excellent performance carb. It'll give you the throttle response you want, and it won't overcarb your engine. Read some of the Thermoquad posts - you'll find a lot of guys here with a lot more experience than me who race them and wouldn't use anything else.

[dwc43]

Originally Posted by blueduster340

Would a 600 cfm Edelbrock or Holley Carb we too small on a 340?

The 340 will have an rpm air gap
hooker headers
comp cams xtreme energy 274H
3.91 gears
pretty much a hopped up performance street car that I would race once or twice a year.
rpm range should be from 1800-6000

I know they came stock with 800 cfm thermoquads but I'll probably go with an aftermarket carb. Also looking for recommendations on what carb I should run on my engine.

The 600 is too small. The edle carbs crack internally and leak, so that's a real bad choice. The stock 340 carb was 800 cfm thermoquad. I'd get a thermoquad and run it. IT will give you the best throttle response and it will stay in tube where a holley wont and you hav no power valve to blow out in a thermoquad. IF you must run a holley get a 750.

[rumblefish360]

How much room under the hood of the Duster do you have? This is where a purchase of some clay to measure the distance is worth the trip to the store.
Don't forget to add some to the measurement for when the engine torques up and moves upward.
Under the hood of my '73 Cuda, I had about a 1/2 inch clearance. This was not enuff when the engine twisted up when I hit the hammer. The air cleaner was damaged.
Installation of a T-Q on the RPM will add the thickness of 2 gaskets and the spacer. 1/2 - 3/4 depending on spacer.
A Holley is a little taller than a Carter type carb.

[fastmopars .inc]

a holley style carburetor, whether it be barry grant or holley made, will give you the best results on your existing intake manifold. whether you go with vacuum or mechanical secondaries will make a lot of difference in streetability and performance. for all out horsepower with acceleration from a stop the first priority, it's hard to beat a 4150 series holley, around 750 cfm. accelerator pumps for both the primary and mechanically operated secondary throttle blades mean that as soon as you can plant your foot that motor is seeing full fuel and full throttle. this also means it will probably use the most fuel in this configuration.
a 3310 holley operates it's primary blades in the same fashion as the 4150 but the secondary's are limited by engine vacuum signals and open slower so an accelerator pump isn't needed before the venturi's draw fuel into the engine. both of these designs are infinitely more tunable than an elderbork and will give you better fuel milage and performance by a long shot if they are properly calibrated. that last sentence is an important one.

[pishta]

TQ was standard on the big valve 340 for only 1 year, 1971. From 68 to 70 it was an AVS that was stock. In 72 they went to the smaller valve J head, and that was about it for the performance of the original 340. The 800 cfm TQ was a better carb as NHRA upped the HP rating for the TQ equipped 340's.

[perfmachst]

hello, the AVS is enough carb for the motor. the originals were around 625 to
650 CFM. right now, the FS/A record is held with a 70 /340 duster, AVS carb, at 122+ mph. if it wasn't enough carb, it wouldn't go 122 + mph. just food for thought. I prefer either the AVS or T.Q. carbs. both will give you
power and fuel milage. a double pumper will not!! good luck,

[blueduster340]

Well the carbs I am looking at are the Edelbrock Performer. They come in either a 600 or 750, Holley 3310 750 cfm, or if I want to spend more money a 700 Holley Double Pumper, or a 650 speed Demon. I'll probably go with one of the cheaper ones for now since I am on a limited budget and I still have to get the car put together. Which would be the better choice. The performer or the Holley 3310?

[70AARCuda]

The holley 3310 is a very good carb..can be used on the street and at the race track with a few adjustments.


tony

[rumblefish360]

I 2nd 70AARCuda's post. Remember this post; "both of these designs are infinitely more tunable than an elderbork and will give you better fuel milage and performance by a long shot if they are properly calibrated. "
By FastMoPars inc.
However, if your handy, a used AVS can be had cheap and rebuilt by yourself for cheap. It is a very easy carb to rebuild. Few parts and no big trick to do it.
I would stay away from a AFB unless you don't mind the secondarys coming in on air demand. The velocity secondary weighted valve isn't easy to modify to come in when you want it to. The AVS has a spring loaded door like a T-Q. Easy to tune with 2 screwdrivers.

[dwc43]

Originally Posted by rumblefish360

How much room under the hood of the Duster do you have? This is where a purchase of some clay to measure the distance is worth the trip to the store.
Don't forget to add some to the measurement for when the engine torques up and moves upward.
Under the hood of my '73 Cuda, I had about a 1/2 inch clearance. This was not enuff when the engine twisted up when I hit the hammer. The air cleaner was damaged.
Installation of a T-Q on the RPM will add the thickness of 2 gaskets and the spacer. 1/2 - 3/4 depending on spacer.
A Holley is a little taller than a Carter type carb.

Good point. Also check the stud lenght. I got a nasty dent from a stud that was too long one time. That never happened again though.

[dwc43]

Originally Posted by blueduster340

Well the carbs I am looking at are the Edelbrock Performer. They come in either a 600 or 750, Holley 3310 750 cfm, or if I want to spend more money a 700 Holley Double Pumper, or a 650 speed Demon. I'll probably go with one of the cheaper ones for now since I am on a limited budget and I still have to get the car put together. Which would be the better choice. The performer or the Holley 3310?

I'd stay away from the edels since they have issuse. Do a search on this board and you will find many complaints about them. IF you want to go with the cheapest and the best, then the stock TQ is what you want. The last one I bought new cost me $185.00. Works great and it's still on the car.

[blueduster340]

another question. Will the Holley 3310 fit on the Edelbrock RPM Air Gap?

[dwc43]

It will, but it's a bad performance choice on the street. No low end throttle response like a thermoquad has.

[fastback340]

I run and Eddy 600 on my 340 wich isnt stock but is by no means wild.. Ive tried 3 other carbs on it 650 and 750 Double Pumpers and a 750 Eddy. The 600 runs the best right now and has been on the motor for 2years no problems.

[fastmopars .inc]

i ran a 3310 holley on my 360 dart as my daily driver for two years. the car got gas milage comparable to my 318 dart which had a carter afb 600 on it.

with 3.23 gears, a factory 340 intake and j heads with big valves and the 284 adv. duration purple shaft in the 360 and a 2500 stall converter, i could mash the gas from a dead stop and incinerate both tires for well over 100 ft. that's without loading the converter, and it also didn't matter how many people were in the car, 1 or 5, the tires would blaze all through first and into second gear.
basically, the car had no lack of throttle response or low end torque. when i put a single plane holley intake on it, and ported/milled the heads, the car had the same low end torque but it made crazy power up top, around the 4500-5500 rpm mark.