750 Holley vs avs2 650 cfm carb for 340?

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1970boy

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Hi looking to upgrade from my carter 1406 600cfm carburetor, looking to gain as much power as I can for the 340, was told different things by different mechanics so wanted to get more opinions, one recomended going straight to the 750 for a noticeable difference not sure if he meant a double pumper or not and the other said the 750 would be too big and I’d be better off with the avs2 650cfm carb. The car sees the street probably 4 days a week and rarely sees the track, either way I want the most bang for my buck to make the most power, what do you all think? Which carb will make me the most power? It’s a 340 with x heads an ld340 intake and hi-po exhaust manifolds with a 3.55 rear
 
I have a 750 Holley double pumper on a stock 360. It performed best (I tried other carbs), E.T. proven. That was with 2.76 gears and stock converter.
 
750 mech (double pumper)holley anyone who recommends a vacuum secondary carb doesn't know how to tune.

IN the way of carburetors. Technology has come a long way since 1960 something. Run a NEW and MODERN carb.
 
I put a 650 AVS2 on my 340 this spring and have been very pleased. I've got a stockish cam, Air Gap intake, and headers. Response is snappy, was easy to set idle air mixture and idle speed. That's all I've done. It does have a slight flat spot or hesitation if you stand on it in some instances but I haven't dug into it. I'm holding off playing with it too much until I get a new cam and heads on. It drives great as-is, isn't stinky and the plugs look great.
 
My answer is the 750 Holley DP, it will out perform the edelbrock
 
I don't know much about carb tuning or really much about anything. I put a new 650 cfm AVS2 with choke on my 340 with headers, exhaust and as far as I know stock otherwise and it's the best thing I've done.

Best thing I've done to the car yet. It's responsive, no lag and spins the tires without even trying. Would buy it again and not even think twice.
 
DentalDart said:
I don't know much about carb tuning or really much about anything. I put a new 650 cfm AVS2 with choke on my 340 with headers, exhaust and as far as I know stock otherwise and it's the best thing I've done.

Best thing I've done to the car yet. It's responsive, no lag and spins the tires without even trying. Would buy it again and not even think twice.
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So you've never used anything else, and have nothing to compare it to.
 
yellow rose said:
So you've never used anything else, and have nothing to compare it to.
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I originally had an Edelbrock 1405 on the car. Compared to that carb this one is night and day.

Compared to the Holley 750 I would not be able to say which is better. Unless someone has used both it's hard to make that comparison I would imagine; no? This is why I only stated that for my application it's been amazing.

I read that holleys were good, but a little harder to tune than the Edelbrock which is why I went with the AVS2, plus I already was set up for Edelbrock with my Lokar kickdown, and it fits under the hood with my RPM air gap and Edelbrock air filter.

Old vs new in pictures.

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1970boy said:
Hi looking to upgrade from my carter 1406 600cfm carburetor, looking to gain as much power as I can for the 340, was told different things by different mechanics so wanted to get more opinions, one recomended going straight to the 750 for a noticeable difference not sure if he meant a double pumper or not and the other said the 750 would be too big and I’d be better off with the avs2 650cfm carb. The car sees the street probably 4 days a week and rarely sees the track, either way I want the most bang for my buck to make the most power, what do you all think? Which carb will make me the most power? It’s a 340 with x heads an ld340 intake and hi-po exhaust manifolds with a 3.55 rear
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Your best bang for the buck is tuning.
That's it.
You want new and shiny. That's differerent. You want boasting material, then bigger is better for those that are into that.
You want better response, or higher mph, or lower e/t then what you need to do is methodical testing.
When everything is tuned, and there's good fuel distribution to all the cylinders, a carb with less restiction equally well tuned will gain some mph in the quarter mile.
 
Holley 3310 is all you need for your combo. If the combo had headers and a steeper gear a 750 DP would be something to think about.
 
Nice choice on the carb. Now its time to get the proper fuel line and metal filter for it. The fuel line kit is $18 on eBay (340 with avs carb). Than get a Wix metal filter for it. Much safer than rubber hose and a plastic filter.


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Johnny Dart said:
Nice choice on the carb. Now its time to get the proper fuel line and metal filter for it. The fuel line kit is $18 on eBay (340 with avs carb). Than get a Wix metal filter for it. Much safer than rubber hose and a plastic filter.


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And don't forget to plug the vacuum port on the lower right. (pics were taken before you plugged that I bet) LOL
I have heard good reports from the AVS2 and Edelbrocks are easy to tune.
 
toolmanmike said:
And don't forget to plug the vacuum port on the lower right. (pics were taken before you plugged that I bet) LOL
I have heard good reports from the AVS2 and Edelbrocks are easy to tune.
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They are some of the best carburetors I've ever seen at running good either out of the box new, or freshly rebuilt with very little adjustment. All of them. The AFBs included. The little Street Demons are the same. I got a 625 Street Demon off Ebay for like 65 bucks needing work. It was advertised as a 750 but I knew it wasn't. It was kinda a bum listing. All it needed was a secondary air door spring and cleaned up and a kit. I put it on the truck and I really didn't need to even adjust the air screws.......but I did anyway. It runs exceptionally well and gets decent mileage for what it is.
 
DentalDart said:
I originally had an Edelbrock 1405 on the car. Compared to that carb this one is night and day.

Compared to the Holley 750 I would not be able to say which is better. Unless someone has used both it's hard to make that comparison I would imagine; no? This is why I only stated that for my application it's been amazing.

I read that holleys were good, but a little harder to tune than the Edelbrock which is why I went with the AVS2, plus I already was set up for Edelbrock with my Lokar kickdown, and it fits under the hood with my RPM air gap and Edelbrock air filter.

Old vs new in pictures.

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I'm not discounting your experience. I was pointing out your limited data because of limited testing.

Mattx gave you the very best advice you'll ever get. Learn to tune what you have. You'll get way more out of it that way than swapping parts.

All carbs, regardless of the name on it, operate on the same science and physics. Once you get a fundamental understanding of that, you can essentially tune any carb. Here's a little fact most people don't know. Every single carb out there is a 100 MPG carb. All of them. Think on that for a minute.

As for tuning ease, the Holley is far and away easier to tune. It's not really even close. And that's not a knock on the Carter/edelbrock stuff. It's just the truth.

The other thing is the Holley has way more tuning options than any other carb out there. Options that are easy and cheap to do. The quadrajet may be the most tune-able carb out there, but it is also the most technical to do, and the least easy to change if you get jacked up on tuning.

Part of the reason Holley gets a bad reputation is that Holley as a company has propagated tuning mistakes and ignorance for decades. And they STILL do it. And they wonder why there are so many carbs out there with screwy tuning on them.

That was my point and I really didn't want to type that much. But it needs to be said. If you study the principles of carburation, it applies to all carbs. If you then take that knowledge and apply it to any carb, you can tune it.
 
1970boy said:
Just curious with those lines could I run e85 if the carb was setup for it?
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I have no experience with E85. The steel lines are available in stainless, if that helps. I would recommend doing some research on the matter.
 
toolmanmike said:
And don't forget to plug the vacuum port on the lower right. (pics were taken before you plugged that I bet) LOL
I have heard good reports from the AVS2 and Edelbrocks are easy to tune.
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Thanks! Yes sir, all plugged up and driving like a dream. I have driven it to school multiple times sinces installing it and haven't had any problems. No more overheating in stop and go traffic in 100 degree heat, haven't experienced what people call "carb heat soak," responsive at every turn is all I've been getting. I did adjust the idle speed screw a little, and will try to tune it a little better one of these days. Probably when I get my new radiator installed.

Johnny Dart said:
Nice choice on the carb. Now its time to get the proper fuel line and metal filter for it. The fuel line kit is $18 on eBay (340 with avs carb). Than get a Wix metal filter for it. Much safer than rubber hose and a plastic filter.


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I was going to get the Edelbrock metal gas line kit, I think it's like 30 bucks or something like that. I got the see through filter because it let me see that I had gas, I'll switch to metal when I get metal lines if they are better though .Thanks for the heads up!
 
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