Eldebrock 600 cfm carb

[Big John]

I may have the wrong set-up its a Eldelbrock P/N 1406 600 cfm square flange electric choke unit. NOT....a vacuum secondary. And my gearing is 3.23 and I did notice stumble/bog during test drive. So, I'm going to place a call to Edelbrock early next week.

Well... That's not really true.

The Edlebrock is a Carter AFB carb. They used these on many cars for a lot of years before the AVS carb was developed. Under the secondary venturi is an air valve. It's kind of a flapper valve that limits the amount of air flow through the secondary bores. The AVS carb is a refinement of that where the air valve is above the venturi and is spring loaded and easier to adjust. The Thermoquad is the same.

While it's true that there are Holley carbs that are true vacuum secondary carbs where a vacuum pot opens the secondary throttle butterflies, the AFB does something very similar. The secondary butterflies open mechanically and the air valve opens with the air flow so you don't get the bog of a mechanical secondary carb. You also have the metering rods in the primary that change the mixture where a Holley just has a fixed jet.

IMHO, the carb you have is far superior than any of the Holley carbs. My preference is the AVS over the AFB, but only because the secondary air valve is more adjustable. Chrysler thought this too. Example: The 350 horse 440 used a Holley and the 375 horse 440 used a Carter AVS.

If it were me, I would drive this car a bit and get the old gas run out of it. Change the plugs and check the timing and then start looking at the carb... I'd probably take a look at the accelerator pump first.

I've always said that most carb problems are electrical, so ALL your ignition needs to be in order... Plugs, timing, cap, wires etc. They all have to be right for these cars to run correctly. They also need to be driven.

 

[Big John]

BTW, I typed all that twice.... The damn intrawebs decided to take a dump just as I hit "reply".

 

[A31PKG]

Sorry if I was not clear: I was attempting to differentiate between the vacuum-actuated secondary throttle plate of the Holley, and the mechanically-actuated secondary throttle plate of the Carter. I did not mean to imply that the Edelbrock was an AVS style carb.

 

[RR383]

BTW..I have the old AVS Carter that sat atop of the original iron intake that came with the car as well. Alright I'll work with what I have.

 

[RR383]

Correct.

That is really just the amount of play in it at full throttle. When the throttle is closed, there should be enough play to let the throttle close all the way without hanging up.

There's a service manual in our reference section and you can download the PDF file. There's a section on how to adjust the linkage and it may help you understand.

http://www.69roadrunner.net/mopar/showthread.php?432-Manuals

I will require the link for the 70 model year..thanks

 

[Big John]

Post #12

 

[Ranger]

This is copied right out of the Edelbrock Performer and Thunder Series AVS manual (which includes the 1406), and unless I am not understanding it, I read it as the secondaries ARE vacuum just as Big John just described.

"Secondary Main System:

The Secondary Main System (Figure 5) delivers fuel only when the secondary throttle blades and air valve are open. It ensures that fuel delivery varies with air flow. The Secondary Throttles (1) begin to open when the Primaries are about 65% open. The Primary and Secondary Throttles arrive at the WOT stop at the same time. Air flow through the Secondary side is controlled by Air Valves (2). These valves are located in the secondary bores above the throttle blades. They are balanced against a counter weight and open to admit additional air flow only if there is enough air velocity to allow the proper operation of the Secondary Metering Systems.

The principles of operation for the Secondary Main System are the same as those that govern the operation of the Primary Main System; the pressure drop (suction) arises from the increase in the airs velocity as it passes through the Venturi sections. The pressure drop (suction) at the Secondary Booster Venturi (3) is communicated into the system by the Secondary Nozzle (4). Fuel flows through the Secondary Main Jet (5) to the Secondary Well where it is drawn through the Secondary Well Tube (6). The fuel is mixed with air that enters the tube through a series of small holes. The source of the air is one of the Secondary Well Bleeds (7). There are two air-bleeds; one admits air to the outside of the Well Tube and the other allows air to flow into the passage behind the Nozzle. The fuel, now well mixed with air, flows through the slightly up-hill passage and exits into the Secondary Boost Venturi (3) through the Secondary Nozzle (4).
In addition to the three (3) basic Metering Systems, there are two (2) Transient Control Systems; The Secondary Auxiliary System and The Pump System.

Secondary Auxiliary System:

During the initial stages of Secondary Operation, the air flow rate through the secondaries is very low. Accordingly, there is not enough pressure drop
(suction) at the Secondary Nozzle to induce fuel flow. In order to prevent a lean A/F condition that would be experienced by the driver as a “bog” or “flat spot” on secondary opening, it is necessary to add fuel by an auxiliary means during the time the secondary is in the transient phase. This is accomplished by placing a small Discharge Nozzle (2) at a point just under the Air Valve (1). The air flow past the edge of the Air Valve creates sufficient pressure drop to pull fuel out of the Auxiliary System. The fuel must first pass through the Secondary Main Jet (3) to the Secondary Well; it is then drawn through the Auxiliary Fuel Tube (4) and exits at the discharge Nozzle (2). There is always an air-bleed, either in the Auxiliary Fuel Tube (near the top), or as a separate brass restriction bushing (shown). The flow of fuel in the Auxiliary System is enough to prevent a lean transient on Secondary opening. As the Air Valve is opened further by increasing air flow, the fuel flow through this system decreases. Correspondingly, the fuel flow in the Secondary Main System increases, providing a near constant A/F ratio."

 

[A31PKG]

Big John is correct....and so was I. Lets not confuse the mechanically actuated secondary throttle plate with the air valve that lives above it. Even with the secondary throttle plate open, airflow through the secondary throttle bore is regulated above it by a counterweighted air valve, or an air valve with adjustable spring (depending on model) which in turn regulates secondary airflow. So in a sense, the secondaries on a Carter do function in relation to low pressure similar to Holley's vacuum diaphragm.

 

[RR383]

Post #12

And where do I navigate to...to open Post#12?

 

[Big John]

This is post #30. Upper right hand corner is a number. ............................................................................................................................^

 

[RR383]

Post 12 was referring to the '69 line-up...I will need for the '70 model year.

 

[Big John]

Post 12 was referring to the '69 line-up...I will need for the '70 model year.

Here's the link in post #12. It takes you to another site.

http://www.mymopar.com/index.php?pid=109

 

[RR383]

Its downloaded.