Carb size question.

[junkpile]

I have a 440 .030 over with a 484/284 cam and 2800 stall converter, 3:23 rear. I currently run an Edelbrock performer 750 electric choke. I have had this carb for many year and have gone thru it at least twice to keep it running with todays gas. I am looking into getting an Edelbrock AVS 2. I recently had some transmission work done at a performance shop and the owner suggested getting a 650 carb for it ( sticking to Edelbrock since car is set up for it). I have never had trouble from the 750 and have run it over 1,000 miles one way to shows up in the northeast from Georgia. My question is, I want to upgrade to AVS 2 but I am not sure if I should drop to the 650 or go up to the 800. The current performer 750 only has a couple changes from "out of the box". I am changed the metering rods (have number wirtten down just not in my brain right now) to allow more fuel to pass the jet when accelerating and using the silver step up spring to hold it richer longer to prevent bogging.

So I would just like suggestions. Should I go up to the 800 avs 2 (still have to add stiffer step up springs) or drop down to the 650 avs 2? Right now I can just happily run on the 750, but it is time for a new carb.

 

[Dipstick]

My opinion, the 650 will give you better driveability/throttle response while the 800 will give you better WOT performance. Which is more important to you?

 

[Budnicks]

For a mainly street driven mild performance combo
like the OP's example is

I'm not a fan of the Edelbrock AVS or AFB knock off's
of the Carter style, in Edelbrock/Webbers

If you want the Carter Look buy an old Carter & rebuild that,
be miles ahead

had a few of them never really were what was expected
I know how to tune them too

if the car sat for any more then 2-3 days was hard starting,
(unless you have an electric fuel pump)
on any of their carbs, AFB or AVS, don't know why all the Edelbrocks do that,
evaporation or something ?, I didn't have any leaks
I never got the 0-60 (or 100) performance out of them
like a Holley did/does or the milage

Personally;
I'd look into the Street Demon 3 bbl, in a 750cfm w/ electric choke
will fit a dual plane manifold with the dividers too
small primaries for decent milage
not foul plugs etc., good for driving around
from Holley now
bolt it on set the idle
& idle mixture screws & don't worry it will be great
I have a couple budies that have used them now
they love em' & haven't touched them either,
bolted them on & set idle to rpm desired
& air set screw in front, to highest vacuum
on 2 mild performance 383 & a 440 builds,
combos, much like the OP's combo

Engine Masters did a 'Cheap Carb Comparison' shootout episode
(If you don't believe me) it was better, no tuning needed out of the box
(The Summit 750cfm brand carb actually won, they don't make it anymore)
& Both other carbs did better than the Edelbrock came in 3rd of the three tested
Street Demon, no tuning needed, right out of the box
& better in performance #s too

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or get a Holley Street Avenger in 770cfm Vac. Secondary w/Elect. choke
of course for more $$$

 

[69 Sleeper Bee]

I would go with an 800 cfm which is closer to stock but if you want better gas mileage the 650 will work but you won't get the top end pull of the bigger carb.

 

[Geoff 2]

The 750 Carter AVS was used on performance 440s. Chry knew what they were doing......
Keep the 750 AFB & spend the money elsewhere.

 

[66 Sat]

I've read that the 800 and 650 cfm AVS2's are really equivalent to 750/600 and need the bigger theoretical size because of the airflow restriction of the annular boosters.
So the 650 would be like putting a 600 on your 440. Too small.

 

[RemCharger]

I like an AVS over an AFB. For a no horsepower type motor, they work well.

 

[RemCharger]

I've read that the 800 and 650 cfm AVS2's are really equivalent to 750/600 and need the bigger theoretical size because of the airflow restriction of the annular boosters.
So the 650 would be like putting a 600 on your 440. Too small.

The flow ratings were different depending if it was dry or wet flowed.

 

[OldGuyGTX]

I have a 440 .030 over with a 484/284 cam and 2800 stall converter, 3:23 rear. I currently run an Edelbrock performer 750 electric choke. I have had this carb for many year and have gone thru it at least twice to keep it running with todays gas. I am looking into getting an Edelbrock AVS 2. I recently had some transmission work done at a performance shop and the owner suggested getting a 650 carb for it ( sticking to Edelbrock since car is set up for it). I have never had trouble from the 750 and have run it over 1,000 miles one way to shows up in the northeast from Georgia. My question is, I want to upgrade to AVS 2 but I am not sure if I should drop to the 650 or go up to the 800. The current performer 750 only has a couple changes from "out of the box". I am changed the metering rods (have number wirtten down just not in my brain right now) to allow more fuel to pass the jet when accelerating and using the silver step up spring to hold it richer longer to prevent bogging.

So I would just like suggestions. Should I go up to the 800 avs 2 (still have to add stiffer step up springs) or drop down to the 650 avs 2? Right now I can just happily run on the 750, but it is time for a new carb.

This may help

CFM Calculator

Get fast, Free Standard Shipping on orders over Summit Racing Equipment from $109 -- no shipping, handling, or rural fees! Exclusions apply.

www.summitracing.com

 

[1967coronet]

I think the 750 preformers are a very good carburetor . You say it is working fine and it sounds like its dialed in pretty well.
If you buy a new one pull the top on your 750 , dump it then blow it dry. Fog it with WD 40 and screw it back together.
I think before its all over you will be bolting it back on.
My 440 has a thermoquad 850 on it that's working fine. I have my 750 preformer sitting in a box ready to go if I need it.
Sometimes its fun just messing around with the carbs and ignition , seeing if you can get a little more out of it. I get it, have fun.

 

[junkpile]

Thanks everyone for the advise. I think you have pointed me in a good direction.

Budnicks- I am trying to stay with a set up that will keep with my linkages so I don't have to mess with kickdown and accelerator distances. its set right and i dont want to mess with it. I have never been a fan of holly carbs (have seen them leak way to often). I will look into the demon. Dont know much about them and the idea of right out of the box working is appealing, although I have always had to adjust something due to my cam.

I believe (if i stay with edelbrock) I will go with the 800 AVS2, try to take advantage of the annular boosters and the fact that I can use my current step up springs to account for low vacuum, see how it runs. I can always change out metering rods if I have to.

this will be a late spring change, as I am currently working on new front brake set up. I will keep every one posted on what goes on.

Thanks again.

 

[ckessel]

One thing with primarily on Holley's and their cousins. Fuel cleanliness is paramount. When you get junk/rust in the metering blocks, it's extremely difficult getting it out. One of the advantages of the Carter's and their cousins. There's no place to hide. Even with the most bad *** filter available, rust gets right by it and plugs things up. Thats where having one or more magnets on the filter and possibly in the tank will save your butt. On my wagon, I have a Mopar[ leftover from my dealer days] trans pan magnet on the WIX 33032 metal fuel filter Its about 2" od with a 7/8" or so id hole, on the inlet side of the filter. I've yet to have any rust issues running my old 3310-2 780. On the Duster I used to own, I had one of the Fram HPG1 chrome canister filters which used a 10 micron filter. I found a replacement Fram element that went down to 5 microns. Rust still got past that. Then I put 4 magnets on the bottom of the canister. No more issues after that.