Edelbrock stumble off idle???

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mopowers

mopowers

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Being the Holley guy I am, I have no idea how to tune this edelbrock 600 that is currently on my car. It seems to have a stumble when you mash the gas. Do these things have accelerator pumps and squiters like Holleys do? How do you adjust this stumble?
 
[ame]http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf[/ame]

See the above
 
For starters make sure the carb is box stock. (Jets,Rods,Springs).
This will let you know exactly where you are starting.Generally these carbs work very well right out of the box,with only minor adjustments.The pump shot arm has 3 holes in it. Stock uses the middle hole. Use the hole farthest from the base,for a larger pump shot.
YouTube actually has a couple really good videos on initial setup/tune.
 
if this just started , I would check out the accelerator pump. ive also experienced the same thing with weak fuel pressure
 
If you're in Sacramento, the factory jetting and metering rods are good to go, but it likely needs idle mixture adjusted for maximum vacuum or maximum idle speed. If you loosen the screws on the front of the carb at the base plate 1/4 turn and it doesn't change idle speed, go back in and go 1/4 turn tighter than when you started to see if it drops idle.

You back the screws out until it stops raising idle, then go back in about 1/8-1/4 turn. Then drop the idle speed to where you want it to idle in RPM and without an 02 sensor, is the best way to gauge lean best idle.

Once you have set idle, it should be pulling correct vacuum to be on the idle circuit of the carb and you can check throttle response after. Do your idle mixture and speed settings first, before accelerator pump or any other adjustments, because that will be the basis on which the rest of the carb runs off of.

If your idle mixture is off and you start doing other things, it will lower vacuum, which can change metering and it also means that your idle speed screw/ primary throttle plate is not where it would be in ideal setting circumstance, so you end up with unbalanced tuning from there, up.
 
Be sure your running the proper fuel pressure. 5-7 psi rings a bell. Outline the engine and which 600 do you have? There is a fuel Economy one and a regular one.
 
No more than 6.0 psi at idle.
if you have a fuel-pressure regulator,set it to 5.5 psi.
 
tekslk said:
Im glad I run Holleys.
Click to expand...
And how exactly are you helping ?
Oh yeah,your not. Way to go !
Got to be one of the most asinine comments ever.
As if a Holley never had an off idle stumble,or some kind of running issue...Wow! Carbs need tunning,even Holleys !
When you make statements like that,you show your level of aptitude.
Maybe in the future,you could be of service ?












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How old is the edelbrock carburetor? How much vaccum does the engine make at idle? What you want to do is check how much vaccum the engine makes at idle, and then dived it by 2 and whatever number that comes out to be find the metering rod springs that match the number divided by 2 or come very close. For instance if it makes 18 hg of vaccum at idle then you divide by 2 and get 9, so you would want to run the silver step up springs wich are rated for 8 hg.
Another thing you can do is swap out the accelerator pump for one with a stiffer spring wich will squirt fuel thru the accelerator pump nozzles better. I beleive the part number for the better accelerator pump with a stiffer spring on it is 1468. And you can also get the accelerator pump nozzle kit, if the carburetor you have is a 1405 then the accelerator nozzles will be marked "28", the kit has a "24" and a "33' and a "43", you could get the nozzle kit and try the "33" nozzles. Another thing that has helped my edelbrock carb alot is a phenolic carb spacer, right now i am running a 1/2 4 hole phenolic spacer and it helped keep the fuel cooler alot.
Last but not least, check for vaccum leaks. I was chasing an off idle stumble on a 1405 for months, tried every rod and spring combo i could, tried all the different accelerator pump linkage holes, tried different accelerator pump nozzles and different accelerator pumps and never could get rid of it. Come to find out the carburetor had a fat vaccum leak right at the primary throttle shaft where my accelerator cable mounted to. All i can think of is i was running too stiff of a throttle return spring and i had it running the wrong way and my accelerator cable was old and stiff, so i think i wore out the aluminum housing that the shaft turns in and it created a vaccum leak.
I purchased a brand new 1806 wich is the edelbrock thunder series 650cfm electric choke carburetor. I purchased a new accelerator cable and a new lighter throttle return spring and a new throttle return spring bracket so i could mount the return spring to pull the opposite way that my accelerator cable pulled on the throttle shaft and i got a new lighter return spring for my throttle valve cable down at the transmission. Now my gas pedal is 3 times softer then it was and i dont have a vaccum leak so my tuning is dead on and the carburetor performes very well.
 
most likely the idle jet is to lean. easy to fix if you know how. but hard to put on paper.
 
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