I tried for 2 years to get rid of that off-idle bog and gave up in the end. The 750 eddy carbs are famous for it, try doing a search around other performance car forums. I tried every mod I read about and although I made some improvement I never did get rid of the bog completely. I bought a double pumper in the end. I've heard that the Thunder series AVS style carbs don't duffer with the same problem. They would still give you that stock look and an 850cfm is available..

I'm surprised nobody has mentioned idle mixture screws yet. Where are they set at. Maybe on a stock cammed engine the normal book setting of 1.5 turns may work but on all my stuff 2.5 or 3 is fairly common and helps with off idle stumbles on automatic cars. I'm sure stick cars would benefit as well.

don.

Just went through this with an 800 eddy. If the car has a bigger cam and poor vac at idle you will get a stumble. First step is a recalibration kit. Get a vac reading at idle. Change the metering rod springs to the color coded set that meets your vac level. If cam is real big and real low vac bump up the initial timing to 18 to 22 degree's and recurve your dist. Mine also ran pretty good with an 850 holley DP. Holley does nopt use vac in the idle circut. Eddy does. Once i cured the stumble i found the eddy was much nicer on a street car then the holley and doesn';t leak fuel every where.;

with a big cam there isn't enough vac to hold down the metering rods during idle. They stay up at full rich. The air/fuel screws do little if anything in this condition. I've only seen this problem with eddies when installed on big cam motors. Mine only had 7 inches of vac at idle in park and 3 to 4 inches at idle in gear. Now with initial timing set at 20 car runs super with no stumble. But did need to recurve the mech advance in distributor to keep total at 38 degrees

Sounds good, I have a mild cam, MP purple .474/280 (if I remember correctly).
I believe I have about 10 inches ov vac at idle. I will verify me vacuum readings on Saurday.
Thanks

I have the thunder AVS. It has same issue with big cams as regular Eddy carb. It's a vac issuse in the idle circut.

I have the same problem with a new Edelbrock 1406 on a very mild cammed 383 4-speed Challenger. The car is simply no fun to drive. Where do you get these "recalibration kits"?

i got mine from summit. You shouldn't be having any trouble with a 4 speed? And a mild 383? What cam? Only seen this problem in big cam motors. Did you try moving the excelerator pump arm to next hole? Eddies have this problem with very low vac readings. Have you checked other things like timing?

I must be the only #1407 Edelbrock 750 cfm AFB carb owner that's happy with their carb. It's 2 yrs old with no problems & very good performance.

Installed a $6 manual hand choke last week and now even starts easy when sitting for a week.

I can pull some threads if need bee - Just let me know , and trust me i talk from experience with the 1407/1411 paper weight about the off idle - And then if you fix that you still have a carb that doesnt perform PERIOD !!!


Some great quotes



Now, in regards to the 750 version, just SAY NO! The carb is a slug. It has the worst signal of anything we have ever tested/dynoed, and is just not an efficient or powerful carb. In plain words it is a . censored
The 500-600cfm versions are great, the 750cfm is unworthy of being on an engine.
Best Regards,

Sam - Pres/CEO
Century Performance Center, Inc.



383 Dyno in "Moparts Tech Archives"



All the aftermarket carbs tested ran fine with the stock calibration except one...the EDELBROCK 750, #1407. this one ran very poorly.....it didnt really do anything well. it was just flat out lean everywhere. idle, part throttle cruise, WOT...and it didnt like to take a load at all. when getting ready to start a pull and going to full power, the motor would fall right on its face, then try to recover....finally recover, and then you could start the pull.
i found this to be pretty interesting because i also had on hand a Carter AFB 750 manual choke version which ran perfectly fine everywhere.
decent throttle response, good part throttle cruise A/F ratios, decent idle A/F ratio with the mixture screws out only 2 turns, and the WOT A/F ratio was right where it should be, and it had a pretty flat fuel curve as well.
i was running short on time, so i just continued on my testing of other things. when i was done for the night i pulled apart the Ebrock carb to see if someone had recalibrated it. this is not a new carb, but was pulled from my friends 396 Chevy yesterday morning. he's been running on the street, and didnt really indicate there was any kinds of problems with it, but there was an indication that another friend of his may have changed some jets or something.
well....that was not the case. it had all the stock jets, rods, and springs, and had no dirt or debris inside. the calibration was just that far off from ALL the other aftermarket carbs.
IMO, the Ebrock carbs are set up for motors that are much milder than what most people are building. well, most people i know anyway
anyway....back to the trenches.....

You guys are so funny!

Maybe my Edelbrock 750 thinks it's a Holley?

You know like a wolf in sheeps clothing.

Plus my mild combo runs high 12's with slicks and as the previous owner included several times slips with the receipts.

want it fixed? put the Holley back on. Don't know why people like to use that 750 Eddy on a BB mopar...

I have had at least three vehicles that somebody put that junky carb on. I just shake my head in disgust.

Wow lots of activity here over the weekend!
I ran the car on Sunday, intake vacuum was 8-9 inches of vacuum at 700 rpm low idle. I moved the mixture screws out an additional 1/2 turn (now 3 turns out), and switched the vacuum advance to the full vacuum fitting, instead of the ported fitting, and the car seemed to run slightly better, but not much. I've been reading the Edelbrock manual and looking for direction there as well, lots of info and combo's for tuning, but no mention (That I found) on off-idle changes.