OK, let's go at this from a different angle. How does the 670 compare with the 3310, with the exception, of course, of cfm ratings? Since I have both (the 3310 needs refreshing), it would be greatly appreciated if I had some opinions of which would be better and why. I'm not opposed to putting some money into the 3310 if it would be the better carb for my application. Strictly a street driven car.

This is on a 70 Duster, with a 340, .030 over, with stock hp manifolds, an Air Gap intake, XE268 cam, and an A833 tranny. Also, a 3.91 geared 8.75 rear diff.

TIA!!!

THe only advantage the 3310 will have won't be seen until above 5000rpm likely.
It may even be a little more responsive on the low end/mid range(and part throttle) with the 670.
IF it is ready to go I would slap it on and go.

The 670 is ready to go (out of the box), but I am willing to put some time and money in the 3310 if it would be worth my while.

The 670 is more than enough for your combo and, as said will probably be a bit crisper on the bottom/mid range.

Why not just freshen up the 3310 and drive them both to see which one you like best? There are a whole lot of variables at work here. The throttle response, cruise-ability, and overall drive-ability will depend as much on the metering as on CFM rating.

So many variables as to how the carb will respond to your particular combo, that I would think that the only way to KNOW which you like best, is to test them both.

IMHO, neither will be perfect out of the box. Least ways, I have never seen one. And you didn't say how comfortable you were with carb tuning.

So you could go with the one that needs the least mods, if you plan to mod at all. Let's face it; most guys just bolt a carb on and if it doesn't behave too badly, they're good to go.

From the responses so far to your posts on this, it seems that there are several members who have experience with the 3310, while there doesn't seem many with experience with the other one. That may matter if you plan on tuning the carb to your combo.

Run them yourself and see for sure which one works the best...........for you.

Well, I'm not too good at carb tuning. Actually, I've never tuned a carb. I did purchase the book "Super Tuning and Modifying Holley Carburetors" by Dave Emanual. If I am to follow the carb formula in this book, the 670 is the best choice, as according to the formula and the section of the book, it can be overcarbureted.

I was thinking of just buying a refreshening kit and maybe an electric choke and secondary spring kit, and playing with the carbs to see which one would feel better. I am hoping the book will give me the information I need to correctly tune a carb.

Anybody here have this book?

Anybody here have this book?

Yes, it will get you about 50% of the way.

With a cam, gears, and a stick, I don't think you need to worry about too much carb.

I'll say it again; you won't know the answer to your question until you try them both on YOUR combo. Besides, think how much you will learn about carbs.

For your combo I would stick with the 3310 750. They have #72 jets in them. Thats fairly rich. I have a Street Avenger 670 on my 75 D300 360 truck. I hate it. It gets hung up on fast idle and wont kick down. It is jetted really lean so it backfires when cold or when I throttle up suddenly. I had a #1850 600 on it befoe and liked it much better. I have had good luck with the 3310, but you might need to put in a lighter secondary spring for the four speed. Maybe the yellow or white one. Get the quick change kit. The 3310 is manual choke so it wont hang up on fast idle. I know i could rework the 670 to make it better, but my choice would be the 750 #3310.

Might I offer a suggestion on the 670? Try a quicker opening Power Valve, like a 9.5 or 10.5. It will bring the enrichment in sooner. 9.5s and 10.5s are all I run on my stuff.

6.5 is just too late to bring the enrichment in many cases in my experience.

As to the choke hanging up, I can't help there. I don't run chokes.

Well, I gotta say, I have never had the choke hang up on my 670. It ran very well on the 340, but that was before it was rebuilt. It had a much higher lift and duration cam in it before, along with a single plane intake (Weiand Xcellerator). Even then, the 3310 ran very rich, and I had to pull the plugs about once a week and clean and dry them. I really don't know what caused that, but I can say that one of the floats stuck and flooded it. At that point, I bought the 670 Street Avenger. I liked the electric choke and the quick change secondary spring feature. I was thinking of adding those to the 3310, along with a refreshening kit.

How can the rich issue be fixed on the 3310?

Avenger carb has secondary metering block and jets, 3310 has metering plate ( no jets to be changed )

The secondary plate vs block won't matter much in this particular application. Here's why;
A)the OP said this is a street car, so dialing in the WOT won't be a priority. As long as there are no problems at wide open, he won't see any need to make changes there.
B)the main jetting (for the vast majority of applications) is the one area that is typically very close, if not dead on with most carbs.

Without an O2 sensor and a decent understanding of the circuits in each carb, most first time tuners are very limited in the changes they can/should make. Having said that, the OP should run the carb that he finds drives the best. That way, he will need to make the least amount of changes.

As the responses here have proven once again; most people like or dislike a particular carb based on how their car runs with the thing out of the box. Not how well it would run the car dialed in for their particular combo.

Neither of these carbs will be the best for every small block Mopar ever built. And that has less to do with their CFM rating, than with the way they are metered.

I personally enjoy tuning carbs. I have used a wide band O2, swap meet carbs, and Emmanuel's book to experiment the last couple of years. I can tell you this about carb tuning for us beginners; IT TAKES A LOT OF TIME!

The more I mess with it, the more I discover what I don't know. What seems to work on one carb, doesn't work the same on another.

For most street cars, all the tuning attention will be directed at the first 30* of throttle movement. That is where most all the street driving happens and where the most circuits must interact. And it is that interaction or overlap that really, really complicates things.

The OP says he wants a good driving carb, not necessarily the fastest carb. He would probably be happy with anything from 600-750 CFM. How the car drives, cruises, and responds is what's important. And that depends much, much more on the carbs metering that on it's CFM.

And the metering on one carb will better suit one combo than another. Which is why different people have different experiences with the same carb on the same size engine. When the combo changes, the carb tune should change.

The carb's metering is way more important than it's CFM for a street car. And what carb works great on one guy's 340, may suck on another guy's 340. Different combos, different tunes.

Both of those carbs can be tuned to your 340. Since you already have both, I would pick the one with the most adjustability and use the other one as a reference since they are both similar in design.

When we tuned the 670 on the Stepson's car the best power valve was 8.5. Made a big difference. I'd like to try a 9.5. He has the same problem with the choke hanging.
When I swapped from the Eddy 1406 t0 the 3310 on my 360 in the Duster daveRS23 set up the Holley. Even without fine tuning it runs great.
Both cars run the XE268 cam.
PM Dave for the Holley mod specs. He has spent countless hours making Holleys streetable and fast.
Ron

So, the only way to change jetting on a 3310 is to replace the metering block?

I've never taken the 670 apart, so I have no idea what jets or power valve are in it. I haven't changed anything from stock, so whatever that is, is what is in it.

""So, the only way to change jetting on a 3310 is to replace the metering block?""
- The secondary side uses a metering plate on the stock 3310. If you swap that plate out for a metering block, then you can change the jets on the secondary side just like the primary side.

""I've never taken the 670 apart, so I have no idea what jets or power valve are in it""
I would suggest that you take the 670 apart and write down what is in it as a baseline. This way you can see how easy they are to take apart and also confirm the jetting and power valve rating.

So, if I do all these modifications, will it cost as much as a new carb?

Man. choke 670 Avenger #0-81670 Factory jets/PV- Primary.-122-65, Sec.-122-68 PV. 125-65 (6.5) Squiter nozzle (.031")

Elec. choke 670 Avenger #0-80670 Factory jets/PV- Primary.-122-65, Sec.-122-68 PV. 125-65 (6.5) Squirter nozzle (.031")

Well, thank you, joedust451!!! So, everything is the same no matter what choke is in use?