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Old 06-24-2010, 09:51 AM   #1
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Edelbrock 750 cfm stumble problem

Does any one have a mild 440 with an Edelbrock 750 carb? There is a stumble on take off but once you get past the first 1/4" of peddle you have to hold on. i have jetted it and changed the metering rods and the springs. any suggestions other than throwing this one away and putting a double pumper on it? Funds are low and the Edelbrock is brand new.
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Old 06-24-2010, 01:09 PM   #2
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I forgot to ask if you have a 750 carb, what jets are you using.
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Old 06-24-2010, 03:49 PM   #3
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Accelerator pump? I have seen many folks [including myself] have to crank-up the idle speed screw to get a motor with a big cam to idle. What happens when you do that is that you start using up some of the stroke on your accel pump shot. So instead of a 30cc pump shot, now you may have 20, or less. Do you have the manual for it?
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Old 06-24-2010, 04:34 PM   #4
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I do have the manual but have done everything it said and it still has the problem. i was hoping to find someone who had the same problem and figured it out.
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Old 06-25-2010, 09:17 AM   #5
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I had a 750 on my 440
what kind of stumble?
does the tach flucuate at all?
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Old 06-25-2010, 09:51 AM   #6
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i talked to a guy at the local speed shop and he said it is a mid range problem and that all the 750's have it when you put a larger cam. He said the larger the cam the less vacuum you have and the Edelbrock does not work well.He suggested to put it on craigslist and buy a Holley. I would think that there is a fix for this, Edelbrock has been around for a long time.
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Old 06-25-2010, 11:04 AM   #7
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I just called Edelbrock and spoke with one of their techs. Looks like Summit Racing strikes again, I am running a Performer RPM intake with the #1411 carb and he said they do not recommend using them together. He also told me that the #1411 750 cfm carb is designed for stock big block engines only. He told me I could play with the jetting but it will not go away since my motor is not stock. The sales people at Summit have given me a bunch of bad info along the way.......
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Old 06-25-2010, 07:56 PM   #8
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do you know when your secondaries open with the edelbrock?
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Old 06-25-2010, 10:07 PM   #9
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Quote:
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do you know when your secondaries open with the edelbrock?
that could play a big role,, the problem with calling a manufacturer is the blame game, not sayn they are right or wrong but it happens alot
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Old 06-26-2010, 06:40 AM   #10
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My carb is a Carter AFB 9605 (same carb as Edelbrock 1405)

I have been struggling with the same problem for weeks.
I finally got rid of the stumble by adjusting the linkage between the primary
throttle and secondary throttle.

I noticed that when I opened the primary throttle all the way the secondary throttle was remaining partially closed. By bending the linkage (to make it shorter) the problem was solved or at least I don't stumble, backfire or die anymore.

good luck
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Old 06-26-2010, 04:16 PM   #11
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i took teh carb apart again and this time i drilled out a set of jets with an 1/8" drill bit for the primary adn put 113 jets in the back. the stumble is almost gone. i read somewhere that you take the vacuum at idle and divide by 2 and that is the springs you should use? can some explain how the springs work for the mopar challenged?
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Old 06-27-2010, 08:57 PM   #12
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I had a 750 edelbrock on my 440, I had the same problem you did, I ended up drilling the secondary enrichment nozzles out, and richening the acc. pump all the way, on a warm day the stumble was gone, on a cool day it was there,

I ended up going with a speed demon 750 with dual acc. pump, first time I hit the throttle on a cool day it lit both tires up.

The first problem with any edelbrock carb is the lack of adjustability, second is that they only have one acc. pump and for a big cubed motor that is bad, get rid of it.

By drilling the jets out in your current carb it will most likley cause problems, at first it sounds good because you are getting rid of the stumble, but as the motor revs it begines the get to much fuel and will cause poor performance and mpgs.

If you have the money look into a good aftermarket fuel injection system, its really nice to be able to turn the key and be done.

edelbrock makes an efi system for the 440's, also proffessional products has a carb looking TBI setup thats tunes itself. nothing else get a holley double pumper.

Alot of people who say holleys are junk are the same people who do not know how a carb works. A holley jet kit has about 40 different jets.....edelbrock kits usually have 8 different jets....go figure
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Old 06-28-2010, 03:43 PM   #13
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some edelbrock's have the adjustable secondaries though

2002ram- also, just double check all of your spark plug wires
make sure they have good connections
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Old 06-28-2010, 09:34 PM   #14
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[quote=440truck;48970 A holley jet kit has about 40 different jets.....edelbrock kits usually have 8 different jets....go figure[/quote]
but several different needles to make up for the"8" jets, theres more than 40 jet combinations with the edelbrock, im not a big fan of eddelbrock but their is nothing wrong with the carbs,
and why is 1 acc pump bad on big cubed engines? it not like the pump is used thru the whole rpm range, the only reason its there is to supply a little bit of fuel at the 1st part of acceration,
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Old 06-28-2010, 09:35 PM   #15
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Quote:
Originally Posted by 67 GTX View Post
some edelbrock's have the adjustable secondaries though
AVS my friend
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Old 06-29-2010, 09:20 AM   #16
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Quote:
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AVS my friend
no, i mean how some avs's have a screw that allows you to change when the secondaries open, without taking the carb. apart
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Old 06-29-2010, 10:24 AM   #17
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Quote:
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no, i mean how some avs's have a screw that allows you to change when the secondaries open, without taking the carb. apart
avs Adjustable Valve Secondarys, afb Aluminum Four Barrel non adjustable
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Old 06-29-2010, 07:28 PM   #18
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but several different needles to make up for the"8" jets, theres more than 40 jet combinations with the edelbrock, im not a big fan of eddelbrock but their is nothing wrong with the carbs,
and why is 1 acc pump bad on big cubed engines? it not like the pump is used thru the whole rpm range, the only reason its there is to supply a little bit of fuel at the 1st part of acceration,
You just answered your own question, the 1 pump only supplies a LITTLE bit of fuel.
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Old 06-29-2010, 07:37 PM   #19
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"Adjustable Valve Secondaries"

Thank you!

The AVS carbs came after the AFB model, and this description plainly describes that there was issues with how the secondary Air Valve opened
on the AFB's. More than likely per application but there must have been a reason for making them adjustable.

Thank you!!!

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Old 06-29-2010, 07:40 PM   #20
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So I have the same issue with my Edelbrock 750 on the 440. Just as I am letting out my clutch, I either have to feather the throttle or rev it up long enough to get the clutch out. It is just on the initial movement from a stopped to clutch out in first gear. After that it works fine. Sounds like what everyone else is reporting. So does the Holley 750 double pumper really cure this? I am frickin tired of dealing with this "feature".
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Old 06-29-2010, 07:43 PM   #21
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Hey '67
is that a 750 AFB or AVS you have?
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Old 06-29-2010, 07:52 PM   #22
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Quote:
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You just answered your own question, the 1 pump only supplies a LITTLE bit of fuel.
you only need a little bit, if it get to much gas it will bog, to little it has a dead spot, theres no need for 2, on the street anyhow,
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Old 06-29-2010, 07:57 PM   #23
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the afb opens kinda like a vacuum secondary, it only opens as much as the engine needs, the afb is a simple carb and works well on the street, the afb is a great carb, the holley is a great carb, little more complex
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Old 06-30-2010, 07:00 AM   #24
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I had the same issue as it seems most of us had. I got mine resolved with adjusting the timing, vacuum, and idle, but was told that I needed to go with the 800 cfm as it runs better on the 440s. The guy who adjusted it for me has been writing for a muscle car magazine for 30 years, and running 440s so I am inclined to believe him as it runs great now. I have the 1411 on there, performer intake, performer rpm heads, performer cam, and it all seems to work great together.
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Old 06-30-2010, 08:51 AM   #25
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Quote:
Originally Posted by 1966sportfury View Post
avs Adjustable Valve Secondarys, afb Aluminum Four Barrel non adjustable
avs air valve secondaries
for edelbrock, they have two kinds of avs's (at least at 800cfm)
one is adjustable from outside the carb, the other one is the traditional one
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Old 06-30-2010, 10:12 AM   #26
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Quote:
Originally Posted by 67 GTX View Post
avs air valve secondaries
for edelbrock, they have two kinds of avs's (at least at 800cfm)
one is adjustable from outside the carb, the other one is the traditional one
edelbrock performer carbs, replaced the carter afb (non adjustable)
1412, 800 cfm manual choke
1413 800 cfm electric choke

edelbrock thunder carb, replaced the carter Air Valve Secondary (avs) (adjustable)
1812 800cfm manual choke
1813 800cfm electric choke
edelbrock calls the avs Adjustable Valve Secondary,
the avs is the adjustable carb, the performer (afb)is non adjustable no matter the cfm
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Old 07-01-2010, 07:48 AM   #27
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Quote:
Originally Posted by 1966sportfury View Post
edelbrock performer carbs, replaced the carter afb (non adjustable)
1412, 800 cfm manual choke
1413 800 cfm electric choke

edelbrock thunder carb, replaced the carter Air Valve Secondary (avs) (adjustable)
1812 800cfm manual choke
1813 800cfm electric choke
edelbrock calls the avs Adjustable Valve Secondary,
the avs is the adjustable carb, the performer (afb)is non adjustable no matter the cfm
well, by adjustable, both can be
just the performer has to be disassembled

I am enjoying this back and forth
but, i think we got our points across now
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Old 07-01-2010, 09:52 AM   #28
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Not so fast!
I want tot know how to adjust the secondary air valve on the Performer (AFB) . I just drilled holes in the weights to adjust mine, is there another way?

Joe.
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Old 07-01-2010, 11:13 AM   #29
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no, theres no other way,,
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Old 08-05-2010, 03:07 PM   #30
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i just put a Holley 850 cfm double pumper on the truck and i will never buy an Edelbrock again! straight out the box it cured all my problems and is like a different truck. I did nothing more than bolt on and adjust the idle.
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