70bigblockdodge
Old Man with a Hat
Damn even this blind squirrel finds a nut now and again.
Edelbrock 1411 off idle stumble
- Thread starter 1Fury1
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Small steps and test drive until the stumble is cured, I think at about 040 (1mm) will do it.
I do belive that Edelbrock is aware of this as some 1406/1405 i've checked have had a bigger idle jet then some other i've checked. I found a 1406 that had a bigger idle jet than another 1405.
Thats another way that sometimes solve the stumble problem.
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This thread got me thinking about my 1411 and the time that I used it with the stumble. It was before I discovered my worn out fuel pump pushrod. I put it back on today and if it behaves, which I think it should now I will put the 1406 on the convertible because I think the Holley that's on that car isn't behaving as good as it should. I will report my findings.
This is a timely thread for me, as I have a friend that wanted an Edelbrock 1411 for his 69 300 with a stock 440 in it. Since he installed a new one he obtained very recently, he has not been able to get rid of a light to moderate acceleration stumble. So he asked me to help, and I experimented with their stip kit and tried various combinations of step up springs and rods/jets trying to improve this issue, to no avail.
After thinking about this more, it seems that if you want an Edelbrock with an electric choke, the only options you have are the the 1406 or 1411 for a 383 or 440, and both of them are fuel economy calibrations more than performance. To get good fuel economy, the changes are achieved in the metering clusters primarily. If you make a light to moderate acceleration off the line, you are relying on the accelerator pump plus the clusters to get you going (pump shot plus idle circuit including the transfer slot - the narrow slots just above the primary throttle blades). The idle circuit includes the metering rod/jet combination plus mixture screws setting and the off idle acceleration depends on the fuel coming out of the idle circuit plus the transfer slots - i.e., idle mixture plus transfer slot combined.
To get good fuel economy, the throttle position in 3rd gear cruising is about the same as the throttle position when doing a light to moderate acceleration from a stop in first gear and the manifold vacuum levels are probably about the same too. I have concluded that to get rid of the off idle stumble, it will require some rework of the cluster, to achieve greater fuel flow through the transfer slots. Yes, this will affect fuel economy slightly, but probably not much, and I would rather have a slight loss in fuel economy rather than put up with an off idle acceleration stumble.
Bottom line, I believe Zwap from Sweden and Kelgar50 above are on the right path. Fooling with the jets, rods and springs and even the accelerator pump settings won't change anything regarding this problem. Been there, and after thinking about it, it makes sense that the clusters are the real offenders. I also wonder whether Edelbrock has made changes in this area from maybe 5 - 10- years ago. I used their 750 carbs in the more distant past without this BS, and very good throttle response, but their newer ones seem to have problems and aren't as responsive. I think I am done with Edelbrock as a result. And I am aware there are all kinds of interactions between which intake manifold you use, whether stock, or Performer or ............ and the camshaft you are using (not to mention axle ratio, stall speed of the torque converter, etc). But given all these aftermarket choices, the only safe way to avoid problems is to calibrate a little rich, not for fuel economy.
Recall that as emission regulations tightened in the late 70s, carburetors went leaner to improve HC emissions, plus EGR rates were increased, all causing endless problems with stumbles and pass-outs on acceleration. I liked when catalysts were introduced to help clean up HC emissions because you could then calibrate richer on off idle acceleration and cruise, and greatly help those problems. Digital Fuel Injection allows engineers to calibrate for very precise conditions under light acceleration differently than under cruise conditions to get both good driveability and good fuel economy/emissions. Carburetors can't distinguish the two.
Thank you Zwap and Kelgar50 for developing effective solutions! I will give them a try.
After thinking about this more, it seems that if you want an Edelbrock with an electric choke, the only options you have are the the 1406 or 1411 for a 383 or 440, and both of them are fuel economy calibrations more than performance. To get good fuel economy, the changes are achieved in the metering clusters primarily. If you make a light to moderate acceleration off the line, you are relying on the accelerator pump plus the clusters to get you going (pump shot plus idle circuit including the transfer slot - the narrow slots just above the primary throttle blades). The idle circuit includes the metering rod/jet combination plus mixture screws setting and the off idle acceleration depends on the fuel coming out of the idle circuit plus the transfer slots - i.e., idle mixture plus transfer slot combined.
To get good fuel economy, the throttle position in 3rd gear cruising is about the same as the throttle position when doing a light to moderate acceleration from a stop in first gear and the manifold vacuum levels are probably about the same too. I have concluded that to get rid of the off idle stumble, it will require some rework of the cluster, to achieve greater fuel flow through the transfer slots. Yes, this will affect fuel economy slightly, but probably not much, and I would rather have a slight loss in fuel economy rather than put up with an off idle acceleration stumble.
Bottom line, I believe Zwap from Sweden and Kelgar50 above are on the right path. Fooling with the jets, rods and springs and even the accelerator pump settings won't change anything regarding this problem. Been there, and after thinking about it, it makes sense that the clusters are the real offenders. I also wonder whether Edelbrock has made changes in this area from maybe 5 - 10- years ago. I used their 750 carbs in the more distant past without this BS, and very good throttle response, but their newer ones seem to have problems and aren't as responsive. I think I am done with Edelbrock as a result. And I am aware there are all kinds of interactions between which intake manifold you use, whether stock, or Performer or ............ and the camshaft you are using (not to mention axle ratio, stall speed of the torque converter, etc). But given all these aftermarket choices, the only safe way to avoid problems is to calibrate a little rich, not for fuel economy.
Recall that as emission regulations tightened in the late 70s, carburetors went leaner to improve HC emissions, plus EGR rates were increased, all causing endless problems with stumbles and pass-outs on acceleration. I liked when catalysts were introduced to help clean up HC emissions because you could then calibrate richer on off idle acceleration and cruise, and greatly help those problems. Digital Fuel Injection allows engineers to calibrate for very precise conditions under light acceleration differently than under cruise conditions to get both good driveability and good fuel economy/emissions. Carburetors can't distinguish the two.
Thank you Zwap and Kelgar50 for developing effective solutions! I will give them a try.
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Well the 1411 performs very poorly out of the box just like I remember so I'm going to try some of these mods too. It stumbles through the whole range of acceleration, the 1406 performs better on my 440 but it still acts under carbureted, it's just a little smoother. I am looking forward to seeing how it performs on my very mild 383.
70bigblockdodge
Old Man with a Hat
So no 1411 for Dave at the Nats? Just kidding. I am going to give this TQ another chance without a sick fuel system, if it does not cooperate I'm buying a thunder series.
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If I can't make the 1411 work on any of my cars Dave, it's yours.
66Newyorker
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I'm not running an Edelbrock right now. But from what I have read in this thread it seems that the guys running the 1411 are having issues at light to moderate acceleration. The 1411 is a 750 cfm if I am correct. A stock 440 or even a mild 383 won't need that must carburetor. For most of our applications a 625 cfm is more than enough. With the 750 the air flow through the carburetor throat (air horn) isn't quite enough to get the Venturi effect flowing. So what some guys are doing is to richen the accelerator pump to mask this until the air flow has increased enough. Go with the correct cfm carburetor than richen it up to run on a big block. Just my 2 cents.
I agree, but the pump shot adjustment still won't get you sufficient pump shot alone, or long enough. I tried.
Smaller CFM carburetors will give you higher cylinder air/fuel charge velocities due to the smaller primary bores generally, yielding better low end torque with only a slight effect on top speed capability. Holley 4160 4 bbls on stock 1969 and 1970 440 standard engines were rated at 600 cfm and performed better off the line than the Carter AVS carburetors rated at 650 cfm on the same engine. But the Holleys wouldn't last due to cheap castings that warped after about 3 years on average and would not run right again. New Holley carbs available these days are nice and will last. And unlike the Edelbrocks, you can get a new bowl vent equipped Holley 4 bbl too, to help with hot restarts and hot weather driving. This is a really bad aspect of the Edelbrocks, IMO for those of us in hot climates.
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Ok so today I took the .031 nozzles out of the 1406 and hogged them out to .040 and installed them where the stock .035 were in the 1411 and put the .035 nozzles into the 1406. What I noticed in the process was that underneath the nozzles in the 1411 lives a spring and a checkball and under the nozzles in the 1406 there is just a checkball, I don't know what happened to the spring but I'm pretty sure there should be one in each carb.
The results were good, on the ride home there was less hesitation and stumbling although not completely smooth so next chance I get I will open up the nozzles to .043 and see what happens.
I need another linkage kit so I can put the 1406 on the 383 to see if there's an improvement over the 10 year old Holley.
The results were good, on the ride home there was less hesitation and stumbling although not completely smooth so next chance I get I will open up the nozzles to .043 and see what happens.
I need another linkage kit so I can put the 1406 on the 383 to see if there's an improvement over the 10 year old Holley.
commando1
Old Man with a Hat
Starting to think Ross was on to something.
F.A.S.T.
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Oh I know he was!
saylor
Senior Member
yes I was just in here the other day, there is a brass squared off niblet that rides on top of the check ball. underneath the squirter.
while cleaning the carb body, I lost the brass niblet in the grass, then found it, then lost it again. 20 minutes later I found it again. its a tiny little dude.
while cleaning the carb body, I lost the brass niblet in the grass, then found it, then lost it again. 20 minutes later I found it again. its a tiny little dude.
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That's interesting, how old is your carb? In the book they call it a pump discharge weight. 1 of mine uses a spring instead.
saylor
Senior Member
ya ok lol now im scared.. i reread your post ^^ - you said SPRING,, i saw no spring in mine. at least i didnt see a spring go flying out when i got the squirter nozzle off there.
mine had the weight on top of the ball, the ball was the last thing to fall out. i guess i figured it was pressure operated i didnt even think about a spring being in there somewhere.
i have another carb that i have not opened the top off of yet. i will carefully look and see what that one looks like.
i do not know the age of the carbs, or how to tell. i got them both used in a horse trade.
- saylor
mine had the weight on top of the ball, the ball was the last thing to fall out. i guess i figured it was pressure operated i didnt even think about a spring being in there somewhere.
i have another carb that i have not opened the top off of yet. i will carefully look and see what that one looks like.
i do not know the age of the carbs, or how to tell. i got them both used in a horse trade.
- saylor
superfragl
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No spring on my 1411
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Yes I imagine the spring took the place of the weight at some point. I do wonder though if the lack of spring in the 1406 is a problem.
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Well they probably switched to the spring because they're cheaper. Do you think the lack of either would cause a problem? Maybe I'll just call Edelbrock tech today.
Edelbrock Tech Line
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1-800-416-8628
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