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Discussion Starter #1
Got a fresh 383, HEI, Elderbrock 600 electric choke ( disabled) vacumm advance.Motor runs like a champ. Just working some bugs out. Idles fine,cruises great but at W.O.T. it backfires,stumbles a little,then it really screams. Any ideas why it back-fires and stumbles? Isnt back-firing a result of running too lean?
 

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very well could be. 600 cm isnt enough for a 383 IMO. try a bigger carb, something like a 750 holley. it may help.
 

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size...

Well it still should run flawless just will not top out like a larger carb...BUT will work fine on your car. We have stock GM cars with 2 bbls that run fine even 396 truck motors cam with 2 bbl carbs so it is NOT the size...

You have a transition issue with the carb ...dirt in an air bleed or idle to metering system transition issue. secondaries not opening quick enough. not enough throttle squirt when you stab the peddle.

What is the intake open plenum or dual plane? The signal could be very weak at lowend transition under the carb with a open/single plane manifold. BUT the 600cfm should help over come that...

Your problem could very well be carb, BUT it is NOT because of the size. Jim
 

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You have a transition issue with the carb ...secondaries not opening quick enough. not enough throttle squirt when you stab the peddle.

Your problem could very well be carb, BUT it is NOT because of the size. Jim
Jim your on to it here.. My first impression is a lean pop too... a transition problem..

in the three major circuits in a carb....

the place your having a problem is from part throttle to wot. which is where the end of the accelerator pump is waining and main circuits are taking the load....
 

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Toss that edelbrock in the garbage and put a 750 vacum secondary holley on it and enjoy! That carb is way too small!!
Don't toss the eddy in the garbage...PM me and I'll send you my address..I'll even pay for shipping...Thanks........
 

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Discussion Starter #7
Thanks for the suggestions. Lets not get into the Holley/ Elderbrock debate.I have both and they perform well for each application,race or street.
That being said i also dont think the size of the carb is the issue. Sprint cup cars have around 600 cfm carbs and they seem to do pretty well. I was thinking it may be the metering rods? Elderbrock carbs are calibrated to bolt on right out of box with fuel economy in mind, not performance.At least mine was. Should i install bigger jets and metering rods? Right direction or not?
To answer a previous question i am running a dual plane rpm air-gap intake.
 

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Thanks for the suggestions. Lets not get into the Holley/ Elderbrock debate.I have both and they perform well for each application,race or street.
That being said i also dont think the size of the carb is the issue. Sprint cup cars have around 600 cfm carbs and they seem to do pretty well. I was thinking it may be the metering rods? Elderbrock carbs are calibrated to bolt on right out of box with fuel economy in mind, not performance.At least mine was. Should i install bigger jets and metering rods? Right direction or not?
To answer a previous question i am running a dual plane rpm air-gap intake.
Sprint Cup cars use a Holley 830CFM carb.
 

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Discussion Starter #9
OOOOOOK, Cup cars run 830 cfm. I think the size of the carb isn't the factor here. Would still appreciate any feedback on why backfire.
 

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OOOOOOK, Cup cars run 830 cfm. I think the size of the carb isn't the factor here. Would still appreciate any feedback on why backfire.
In most cases of a backfire is a lean or even a rich condition.

Check vacuum lines, intake seal, carb seal. Any leak will cause a lean condition.

Fuel pressure!!!! Very important.

Al
 

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Got a fresh 383, HEI, Eldelbrock 600 electric choke ( disabled) vacuum advance.Motor runs like a champ. Just working some bugs out. Idles fine,cruises great but at W.O.T. it backfires,stumbles a little,then it really screams. Any ideas why it back-fires and stumbles? Isn't back-firing a result of running too lean?
Which is disabled the choke or vacuum advance and why?

You might have the choke flapper slamming shut and then opening. The momentary rich mixture ignites when the flapper opens.
If it's a momentary lean back fire then the secondaries may be opening too quick. Not sure how they function on the Edelbrock but I'd look at that.

I'd also look at the HEI advance mechanism. Find a shop with a distributor machine and have it spun up.
 

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Discussion Starter #14
Thanks to all that gave me a few constructive things to trouble shoot. I think I'll stop short of throwing my Elderbrock away. If i did that evertime something didn't work right ,I'd have more trash cans than cars. I've had plenty of Elderbrock's with minimal problems. To those dedicated Holley owners, Im glad you found something you like, As long as it's between the fenders of a Nova.
 
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