Carburetor size

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70Duster340

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After watching the video on sizing a carburetor, I was wondering if using the carb that I have (Holley 670 Street Avenger) would be too much carb for the engine. It's going on a 1971 340, rebuilt with. 030 over forged pistons and Edelbrock aluminum heads. Using the calculator, the carb should be around 487 cfm. This will be used as a street car. It's going in a 1970 Duster.
If I left out any pertinent information, I apologize.
 
That carburetor will be about perfect. Those calculators are stupid.
 
To quote Carl Sagen; there are "billions and billions" of Holley 750's resting comfortably on 383's, so 670 has to be about dead nuts perfect on a 340. My 2 cents. Lefty71
 
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Piss on that calculator.
After 45 years of racing, and or driving hoped up 340's I personally like a Holley 750 DP.
I do not think the carburetor you have would be too much.
You never said any thing about headers, but I am sure you have them on the car.
 
If you already have the 670, that will work fine. It may be a bit under carbed for optimal performance but you'll be happy with it.
 
70Duster340 said:
After watching the video on sizing a carburetor, I was wondering if using the carb that I have (Holley 670 Street Avenger) would be too much carb for the engine. It's going on a 1971 340, rebuilt with. 030 over forged pistons and Edelbrock aluminum heads. Using the calculator, the carb should be around 487 cfm. This will be used as a street car. It's going in a 1970 Duster.
If I left out any pertinent information, I apologize.
Click to expand...
I'm using the Street Demon 1901 and my 340 never performed as good as it does now. After dialing it in, it starts right up and the plugs are a nice tan.
 
In '71 the 340 got a 800 cfm spreadbore, up from the previous 650 Avs. So the 670 is probably adequate but you could go bigger.
About 25 years ago at the suggestion of Dick Landy I put a #3310 750 vacuum secondary with 2 metering blocks on mine based on my combo. No problems, as of yesterday still on there running fine.
Landy said with the vacuum secondary it would only get more gas if it needs it. There are better choices out there now. Edelbrock makes an 800 now that dynos better on a 340 than the 3310.
 
70Duster340 said:
After watching the video on sizing a carburetor, I was wondering if using the carb that I have (Holley 670 Street Avenger) would be too much carb for the engine. It's going on a 1971 340, rebuilt with. 030 over forged pistons and Edelbrock aluminum heads. Using the calculator, the carb should be around 487 cfm. This will be used as a street car. It's going in a 1970 Duster.
If I left out any pertinent information, I apologize.
Click to expand...
You left out a ton of information, but that doesn’t matter because the first thing to inform you about is the video and calculators are dumb and wrong on so many levels I’m not going to waste 10 pages of cyberspace listing and explaining the how, why and what should be. The calcs are moronic at the mildest and nicest description.

The calculators are telling you what the engine can consume. What you’ll find is if you put a 500 cfm carb on top, (13 cfm more than the calculators say) is that the car will be under powered, slow and constantly in the secondary side just to get moving.

If there is any doubt, I point to 2 sources of actual real information in history and current use as we speak.

1: Chrysler’s 340 engine first used the small primary TQ. Then moved to the larger primary TQ. This had an actual flow over 760 cfm. On a STOCK 340!

2: Speak with the drag racers here and they tell you that for Dudley, “More carb the merry.” (Within reason of the build and the duties it drives under.)

Use what ya got for now.
 
Use what you have.
You may have to richen it up a little, the street avengers seem to be set lean from Holley.
 
Well, as for the info that I left out, it's a 4-speed car, with an 8.75 rear diff with 3.91's. Stock manifolds, manual steering. HE268 cam. When I bought the car, it had a 3310, which ran very rich and was constantly flooding out the engine. So I switched to the 670, which ran much better with no flooding issues, and tan plugs. I never really had a chance to really get on it to see how it performed, though.
 
70Duster340 said:
Well, as for the info that I left out, it's a 4-speed car, with an 8.75 rear diff with 3.91's. Stock manifolds, manual steering. HE268 cam. When I bought the car, it had a 3310, which ran very rich and was constantly flooding out the engine. So I switched to the 670, which ran much better with no flooding issues, and tan plugs. I never really had a chance to really get on it to see how it performed, though.
Click to expand...
flooding the engine had nothing to do with the 3310's size, but the fact that something was wrong with it or it was completely set up wrong for your car. I have a 750 double pumper on a stock 360, works flawlessly
 
318willrun said:
flooding the engine had nothing to do with the 3310's size, but the fact that something was wrong with it or it was completely set up wrong for your car. I have a 750 double pumper on a stock 360, works flawlessly
Click to expand...
Amen & I was about to edit my post and suggest a double pumper. Being a 4spd w/3.91 gears. Oh yea, DP all day long!
 
70Duster340 said:
After watching the video on sizing a carburetor, I was wondering if using the carb that I have (Holley 670 Street Avenger) would be too much carb for the engine. It's going on a 1971 340, rebuilt with. 030 over forged pistons and Edelbrock aluminum heads. Using the calculator, the carb should be around 487 cfm. This will be used as a street car. It's going in a 1970 Duster.
If I left out any pertinent information, I apologize.
Click to expand...
That carburetor is a piece of **** for anything beyond a stock or RV cam'd sb.
Everything about it is aimed at performance economy, more so economy.
You will find a lean spot you can't rid without changing bleeds...and they pressed on that carb, pita to change them...better off buying a quick fuel of similar cfm rating.
Did this same dance with the last 340 I did for Spinman, wide band hooked up
 
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sireland67 said:
Use what you have.
You may have to richen it up a little, the street avengers seem to be set lean from Holley.
Click to expand...


yes.

and if the OP is like me and not the greatest with jetting, fine a chassis dyno with an AFR. DOne deal
 
An Air/fuel gauge is a great tuning tool.
I have a AEM one in my Duster.
 
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