Stumble issue

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69dart440

69dart440

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I have a 69 Dart with a 1972 440 in it. My issue is that it has a bad stumble right off idle when I just try to pull out lightly and also when Im just cruising barely on the gas. If I give it a little more gas its ok or if I punch it, it will get better. Also I noticed that if Im at wide open throttle I get a little bit of detonation at higher rpms and when it shifts into 2nd it seems to fall on its face. It has an edelbrock 750. Has a mopar electronic ignition and timing is 18 degrees base and 36 total. Any help would be great. Dont know if my issue is timing or carburetor. Thanks!

Josh
 
Sounds like a carb problem, check the pump in the carb. With the motor off, open up the choke, look down the primary side, see if you have 2 steady steams of fuel flowing when you (quickly) open up the throttle.
 
Search function is your friend on this question. Probably 5-10 threads already on this with tons of answers.

That being said, my stumble issue was in the idle mixture screws adjustment. An hour or two of tuning fixed it right up.
 
I'd start off by backing your timing down to 12 deg initial, 18 is usually to much unless you're running 102 octane and disconnect the vacuum advance if you haven't allready. If 12 works better you'll have to recurve the dizzy for 36 total at 2200-2400 RPM. Do you know what your comp. ratio is and what kind of heads.
 
demon seed said:
I'd start off by backing your timing down to 12 deg initial, 18 is usually to much unless you're running 102 octane and disconnect the vacuum advance if you haven't allready. If 12 works better you'll have to recurve the dizzy for 36 total at 2200-2400 RPM. Do you know what your comp. ratio is and what kind of heads.
Click to expand...

I was told they were 77 heads and 9.5 to 1 compression but I dont know for sure. Yes I do have the vacuum advance plugged. I will try to back the timing down and see what happens. Thanks for the help guys!
 
Classic Edelbrock carb behavior. I tuned and tuned and tuned my Edelbrock 600 on my 340 and never got rid of that off idle stumble. I put a Holley 650 DP on it, sold the Edelbrock and never looked back. Also gained 4 mph in the 1/4 mile.

My advice - get a Holley Street Avenger 750 and you'll be happy camper.

Regarding the comment about disconnecting the vacuum advance - bad idea on street car. Get an adjustable vac advance. You may need to play with the initial, the total and the adjustment of the vacuum advance to get things right. But removing the vac advance should only be done on racecars.

The Feb Mopar Action has a great article about vacuum advance - why you need it and how to adjust it.
 
lilcuda said:
Classic Edelbrock carb behavior. I tuned and tuned and tuned my Edelbrock 600 on my 340 and never got rid of that off idle stumble. I put a Holley 650 DP on it, sold the Edelbrock and never looked back. Also gained 4 mph in the 1/4 mile.

My advice - get a Holley Street Avenger 750 and you'll be happy camper.

Regarding the comment about disconnecting the vacuum advance - bad idea on street car. Get an adjustable vac advance. You may need to play with the initial, the total and the adjustment of the vacuum advance to get things right. But removing the vac advance should only be done on racecars.

The Feb Mopar Action has a great article about vacuum advance - why you need it and how to adjust it.
Click to expand...

Awesome! Thanks a lot for the help!
 
Also check the to see if the accelerator pump shoots as soon as the throttle is cracked. If it does not, the carb is letting more air in and no fuel----
-----lean stumble.
 
Should the vacuum advance be hooked to ported or non ported?
 
First off, open up the top of the eddy carb, pull the airhorn off and check float level and drop to see if it is in spec. Float drop can cause this. Also check the little filter screens above the needle/seat assemblies. Eddys can be very good carbs.
 
Ok so I hooked the vacuum advance up today and had no change, still stumbles off the line. Checked the accelerator pump and looks good, shoots plenty of fuel. I also thought I would try heavier springs for the metering rods in the eddy carb but when I pulled them out, it already had the heaviest springs in. Not sure what to do next. Also i took it for a drive and punched it and when it shifts into 2nd it boggs and falls on its face. What would cause this? Thanks for the help guys. Hope to get this figured out cause this thing feels like a torque monster.
 
Put the next lighter springs and drive again, and maybe again. The spring kits are not that expensive.
 
There have been many threads about the stumble issue with the Eddy 750 don't waste your time.I chased this problem on my 360 for most of the summer,jets,metering rods,springs,discharge nozzles and everything else nothing corrected the stumble.I changed the carb to the EPS 800 and the car ran great with the carb right out of the box and even better when it was dailed in.
 
I read somewhere that the pump shooter height was too high,not the arm position,needs to be bent back down so it wont lift the plunger to high in the bore,I'll see if I can find it.
 
Bend the accelerator pump rod so that only 13/32" of the acelerator pump shaft is sticking above the carb body and I bet your issue disappears. The Edelbrock pump is typically so high in the body that it is above the transfer slot. When you tip in it just pushes fuel back into the float bowl and not top the accelerator pump squiirters. That little trick has cures 99% of the off idle stumbles I've ever seen in the AFB carbs.Also check Fugly racing afb write up
 
Take the carb off,and put it on the bench.
Take the top off,and check the float height. They are notorius for improper float height.
With a compressor,blow out all air/fuel passages.
Dirt particles can kill any carb.
Screw top back on.
Bring back to stock settings with Orange spring/Metering rod.
Turn a/f screws out 1 1/2 turns.This is just to start,and will need to be fine tuned.
No vacuum advance at this point. Plug both sides.
(I dont run it at all,its a Muscle car for gods sakes)!!!.

My choke is manual and wired open. Either way make sure your choke is opening all the way,and out of the question.

Bog off idle can be your pump shot.Move to the hole closer to the carb body for more of a pump shot.

Springs are for power mode,not idle. Lighter spring will open up the metering rod sooner,giving you more fuel quicker.It could be falling on its face because it needs more fuel quicker.Start at orange,and go lighter if the problem persists. Heavy springs are for heavy cars,opening the power mode slower.

Measuring your manifold vacuum will let you know what spring you need,but like I said start with the orange. Ede are calibrated very close out the box.

Not sure if you have the manual for your carb,but if you dont your tunning in the dark. You can look it up on line.Get your self the calibration kit. Once you know the principles,there cake.



Or you can get a Holley and tinker with it more than a British motorcycle.:-D
 
Johnny Dart said:
Take the carb off,and put it on the bench.
Take the top off,and check the float height. They are notorius for improper float height.
With a compressor,blow out all air/fuel passages.
Dirt particles can kill any carb.
Screw top back on.
Bring back to stock settings with Orange spring/Metering rod.
Turn a/f screws out 1 1/2 turns.This is just to start,and will need to be fine tuned.
No vacuum advance at this point. Plug both sides.
(I dont run it at all,its a Muscle car for gods sakes)!!!.

My choke is manual and wired open. Either way make sure your choke is opening all the way,and out of the question.

Bog off idle can be your pump shot.Move to the hole closer to the carb body for more of a pump shot.

Springs are for power mode,not idle. Lighter spring will open up the metering rod sooner,giving you more fuel quicker.It could be falling on its face because it needs more fuel quicker.Start at orange,and go lighter if the problem persists. Heavy springs are for heavy cars,opening the power mode slower.

Measuring your manifold vacuum will let you know what spring you need,but like I said start with the orange. Ede are calibrated very close out the box.

Not sure if you have the manual for your carb,but if you dont your tunning in the dark. You can look it up on line.Get your self the calibration kit. Once you know the principles,there cake.



Or you can get a Holley and tinker with it more than a British motorcycle.:-D
Click to expand...

I though a heavier spring opens the power mode sooner? I do need to check my fuel pressure. Probably should have been one of the first things to do. I already have a calibration kit. Thanks again guys. I hate to get rid of it, but a lot of people say to get a holley they work good out of the box.
 
69dart440 said:
I though a heavier spring opens the power mode sooner? I do need to check my fuel pressure. Probably should have been one of the first things to do. I already have a calibration kit. Thanks again guys. I hate to get rid of it, but a lot of people say to get a holley they work good out of the box.
Click to expand...

Actually the Edelbrock carbs are known as the most forgiving or out of the box carb you can buy. If you cant tune an Ede properly forget about getting a Holley dialed in. Not saying Holleys are bad carbs,they are great carbs,just have to know what your doing when setting them up.

Heavier spring opens the rods later in the power mode.When engine is under a load vacuum drops.When vacuum drops a lighter spring will open the rods easier than a heavier spring.

Like I said you are tunning in the dark. Look up the manual on the Edelbrock site,and get a better understanding on how it works. If you dont know what your doing,you cant blame it on the carb !


Start with the factory ORANGE Spring & metering rod.
 
Johnny Dart said:
Actually the Edelbrock carbs are known as the most forgiving or out of the box carb you can buy. If you cant tune an Ede properly forget about getting a Holley dialed in. Not saying Holleys are bad carbs,they are great carbs,just have to know what your doing when setting them up.

Heavier spring opens the rods later in the power mode.When engine is under a load vacuum drops.When vacuum drops a lighter spring will open the rods easier than a heavier spring.

Like I said you are tunning in the dark. Look up the manual on the Edelbrock site,and get a better understanding on how it works. If you dont know what your doing,you cant blame it on the carb !


Start with the factory ORANGE Spring & metering rod.
Click to expand...

I have the manual. It says that if you have a stumble issue at light throttle to go to the heaviest spring.
 
69dart440 said:
I have the manual. It says that if you have a stumble issue at light throttle to go to the heaviest spring.
Click to expand...


Wrong. If you have a stumble at light throttle (Cruise mode) you have a lean condition. Look at you chart and go 1 stage Richer untill problem is cured.

Like I said before. Springs are for the POWER MODE.



Questions for you.
Have you checked your float level ?
Do you know your vacuum ?
What color spring do you have in there now ?
What metering rod do you have in there now ?
Which hole in the pump arm do you have it ?
You never told us Manual/electric choke ?
 
Johnny Dart said:
Wrong. If you have a stumble at light throttle (Cruise mode) you have a lean condition. Look at you chart and go 1 stage Richer untill problem is cured.

Like I said before. Springs are for the POWER MODE.



Questions for you.
Have you checked your float level ?
Do you know your vacuum ?
What color spring do you have in there now ?
What metering rod do you have in there now ?
Which hole in the pump arm do you have it ?
You never told us Manual/electric choke ?
Click to expand...

Have not checked float level.
Dont know vacuum.
Silver spring in now. (heaviest)
I think the metering rods were 6842. Which seems very rich to me.
Its in top hole on pump arm.
Electric choke. Choke seems to work great.

I know I have to to my homework and check float level and vacuum. I just dont have a vacuum gage right now. What should float level be at? Also should probably look at jets when I have the top off.
Again thanks for the help!

Josh
 
69dart440 said:
Have not checked float level.
Dont know vacuum.
Silver spring in now. (heaviest)
I think the metering rods were 6842. Which seems very rich to me.
Its in top hole on pump arm.
Electric choke. Choke seems to work great.

I know I have to to my homework and check float level and vacuum. I just dont have a vacuum gage right now. What should float level be at? Also should probably look at jets when I have the top off.
Again thanks for the help!

Josh
Click to expand...

Ok....
Heres the set-up you need to follow. You have your carb set-up completely wrong.Cant keep going back and fourth if your not going to listen.Dont take this the wrong way,just trying to help.The reason you have a stumble off the line is because of your pump shot. Wrong hole,farthest out is the least amount of fuel.The car is falling on its face because it has the heaviest spring in it,thus not opening the metering rods fast enough,if at all in the power mode.
THE CAR IS STARVING FOR FUEL !

:Bring this carb back to stock calibration: 1411 Edelbrock
Main Jet-1432 (.110")
Secondary Jet-1431 (.107")
Metering Rod 1459 (.075"-.047")
Center Hole Pump arm.
7/16" Float level
"ORANGE" Spring
A/F screws out 1.5 turns
Make sure the choke COMPLETELY opens when hot.

Do this and then tell me what its doing.

By the way,have you checked for any vacuum leaks ?
 
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