67 - 273 4bbl and 69- 340 4bbl

[wlecat]

do the above share the same Carter 4bbl carb?
if not what stock model did the 340 use?
I have a Holley 750 DP on mine now and it's a roob job. Advice please.

 

[Rocky_JS]

no 67 was AFB and in 69 would have been an AVS

 

[nothingbutdarts]

no 67 was afb and in 69 would have been an avs

x2

 

[wlecat]

What is the basic difference between AFB & AVS?
Does anyon know which Carter model would have been on the 69 340?

 

[Rocky_JS]

AFB Aluminum four barrel, AVS air valve secondary both are made by carter. Without looking it up I think the AFB used a counter weighted secondary (mechanical) and the AVS was spring loaded (vacuum operated). On a 69 340 it would have been an Carter AVS.
Either will work interchangeably. with the AVS being an updated version I think starting in 68.

 

[perfacar]

hi, the 273 had 478 CFM afb carb, with counterweight sec air valve. the 340 had a 625 CFM avs, it has an air door in sec.more easier to tune for jetting. the throttle bores are different sizes also. the avs will require boring out bores in manifold to use it. just food for thought

 

[Rocky_JS]

correct there is a slight difference in bore diameter in the secondaries where the 67 AFB is the smaller of the 2, but the AVS should be the same bore as the holley you currently have.
If you are using the 67 intake as stated you either need to bore the secondary openings or use a small spacer. I used a gasket thick spacer and 2 base gaskets and that worked.

 

[69 Cuda 440]

Carter Carburetors

1967..........273 4-Barrel

#4294S or #4295S (Factory Advertised as a 500 CFM w/Mechanical Secondaries)
Primary.........1 7/16"
Secondary.....1 9/16"
----------------------------------------------------------------------------

1969..........340 4-Barrel

#4611S or #4612S (Factory Advertised as a 625 CFM w/Vacuum Secondaries)
Primary..........1 7/16"
Secondary......1 11/16"

 

[wlecat]

for some reason I recall the 67 secondarys being considerably larger than the primarys.
the Holley is sitting on a 340 intake
btw, what was the stockpaint color for the 273?

 

[Rocky_JS]

67 secondaries are smaller. 340 intake can use any square bore carb I know of save a dominator. stock 67 273 engine color is red.
Are you using a 340 intake on 273 heads? That is a pretty big port mismatch going the wrong way.

for some reason I recall the 67 secondarys being considerably larger than the primarys.
the Holley is sitting on a 340 intake
btw, what was the stockpaint color for the 273?

 

[wlecat]

it is a 340 with a 34o intake. I've been told the Holley is way too big and an edelbrock 550 would work nicely

 

[crackedback]

too big... nope...

Run 750's on 340's all the time.

 

[69 Cuda 440]

Agree Crackedback,,,,,,

A Carter 750 AVS works well with a Street 340.

Equal Square Bore........1 11/16" x 1 11/16"

I've used many Carter 750 AVS carburetors off of an old 440.

Carb Numbers.......#4617, #4618, #4737 or #4739

The Jet Sizes....{.101" Primary) and {.095" Secondary} should be stepped down to;

To {.095" Primary} and {.092" Secondary}

Great Carburetor for a 340....and cost productive as well.

 

[wlecat]

I don't expect the same out of a 340 but my stock carter AFB got @23 mpg with a 273 in a 67 AT dart with 3.23 PT rear and could still tear it up. What do you guys get?