Edelbrock Carb Spring Change-Out

[Ron H]

I have an Edelbrock carb on after complete engine rebuild and came across a kit that's available for adjusting containing springs of various tensions and a video clip I've pasted below. It doesn't get into any details though about exactly what this accomplishes. If anyone has done this change-over would like to know more. Thanks

 

[BeepBeepRR]

The springs and metering rods are specific to how many Hg of mercury your car is pulling. If your car pulls 8hg of merc you use a specific rod and spring combo. Or if it pulls 15 you change it to another combo. It is all in the kit and the directions are somewhat simple to follow.

As for jets I assume that is kind of like a holley, want more fuel? Put bigger jets in. However you will have to butt dyno jet changes. And remember too much fuel is not a good thing.

You need a vacuum gauge to see what kind of mercury your setup is pulling. Hook it up to the non metered port on your car base. I think its the one on the right bottom. Start the car and see what kind of vacuum you have and adjust from there. The picture below shows on the right the metering rod and spring combos. The guys here probably know more about jet changes than I do so wait for others to chime in.

 

[moparedtn]

Lots of help also in the instructions that came with the carb, as well as on the Edelbrock website.
There's a ton of videos on YouTube on it as well.

 

[threewood]

Simply put, while idling the springs and rods should be held down. When the car is revved they pop up due to reduced vacuum and expose the thinner part ofthe rod = more fuel.

Loosen the two rod covers and swivel them over so you can see the rods / pistons. Tighten down and start car, they should be held down. If they are bouncing or up you need a weaker spring. Blip the throttle and they should pop up and fall back down when the car returns to idle.

 

[chtampa]

I did it, but I cheated a bit and used an O2 Reader.

 

[RJRENTON]

Gentlemen,
USUALLY, Mopar used Carter AFB or AVS carbs and most used three (3) step primary step up rods. It was easy to tell because the 3 step rods and step up pistons had a domed cover; the 2 step up piston assembly used a FLAT cover plate.
The 3 step metering rods (and corresponding pistons) provided a smoother transition for primary fuel metering from cruise to power air fuel ratio.
REMEMBER, when turning the fuel system the key is AREA PRESENTED in the jet/metering rod ratio. It must be calculated to get the effective AREA by measuring the diameter of the metering rod step diameter and converting this number to square inches. The jet diameter is known, so convert the jet otifice diameter to AREA in sauare inches and SUBTRACT the metering rod step area to get the accurate jet presented area. You cannot just subtract diameters as area varies as the square of the diameter. Fuel feeds are usually calculated in pounds/hr or air/fuel ratios from stochometric (14:1) to best power ratio (spprox 12:1) allowing for uniform distribution.
Carter carbs are easy to tune....it just takes a little common sense and time.

 

[Ranger16]

Maybe this will be of some help. Read the part about "CALIBRATING THE POWER MODE STAGING".
http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

 

[lewtot184]

Gentlemen,
USUALLY, Mopar used Carter AFB or AVS carbs and most used three (3) step primary step up rods. It was easy to tell because the 3 step rods and step up pistons had a domed cover; the 2 step up piston assembly used a FLAT cover plate.
The 3 step metering rods (and corresponding pistons) provided a smoother transition for primary fuel metering from cruise to power air fuel ratio.
REMEMBER, when turning the fuel system the key is AREA PRESENTED in the jet/metering rod ratio. It must be calculated to get the effective AREA by measuring the diameter of the metering rod step diameter and converting this number to square inches. The jet diameter is known, so convert the jet otifice diameter to AREA in sauare inches and SUBTRACT the metering rod step area to get the accurate jet presented area. You cannot just subtract diameters as area varies as the square of the diameter. Fuel feeds are usually calculated in pounds/hr or air/fuel ratios from stochometric (14:1) to best power ratio (spprox 12:1) allowing for uniform distribution.
Carter carbs are easy to tune....it just takes a little common sense and time.

jet area!!!! this is what I do. reading the manual that comes with the carb should be the first step.

 

[chtampa]

My 4615 has the original step up springs in it but when I install the rods on top they do not sit proud in the wells. The covers can just lay over the top without any pressure to hold them down. Should they be higher? Are the springs too collapsed?

 

[threewood]

My 4615 has the original step up springs in it but when I install the rods on top they do not sit proud in the wells. The covers can just lay over the top without any pressure to hold them down. Should they be higher? Are the springs too collapsed?

Unless the setup is different from the newer Edelbrock AVS, I would say your springs are worn out. The step up piston/spring/rod on my Eddy AVS will push the covers up as I loosen the screws.

 

[chtampa]

Unless the setup is different from the newer Edelbrock AVS, I would say your springs are worn out. The step up piston/spring/rod on my Eddy AVS will push the covers up as I loosen the screws.

The Edelbrock springs are a much taller design than the originals.