Carb soft, break up of ignition at 3000k

[billschroeder5842]

I have a mostly stock 383 with a super mild cam, headers, Alum intake and a performer carb. I have that usual Eddy soft spot on take off and I (mostly) masked it through advancing the timing. The down side of advancing the timing is that the motor breaks up about 3000.

I retarded the timing and that seemed to take care (mostly) of the break up but the soft spot is back with a vengeance. It was suggested by a local car buddy that I moved the vacuum tube from the "carb" side to the "manifold" side and that seemed to help the soft spot.

I'm living with this situation at the moment because I rarely get up over 3000k as I do mostly town driving. The engine is running real well, starts up instantly and idles pretty smooth.

Any ideas on getting rid of the soft spot AND eliminating the higher rpm break up?

[Budnicks]

1st I would go to Edelbrocks web site, they have some very common fixes... what model # & Performer carb 550, 650, 750cfm ? is the fuel pump adequate ?, have you checked the fuel filters ?, is the float level correct ?, what ignition timing are you running ?, when does the total advance come in ? how many degrees is the vacuum advance adding ?, also if needed get the proper, accelerator discharge pump nozzle/squirter size, jetting & metering rods, for your specific engine combo, I would make sure all the external settings are all correct, before you buy anything, but they have the fixes & parts available, there are a ton of threads about the exact subject you talking about here & many other Mopar specific sites... I'm going to be a smart a$$ & say to buy a Holley DP, ProForm or QuickFuel Holley based carb, it seems that almost everyone that uses the Eddy Performer carb has that very problem... Just my opinion....  Here's a couple of spots to look into, there are more but I could only post those for some reason.... There are a couple of guys here that love them maybe one of them will chime in, 71Bee seems to be kind of an expert on them... Search him out maybe...

[billschroeder5842]

Thanks for the direction on this one-I'll need to read up on this one. I've had Holleys for years and this is my first Eddy. I'm not real impressed so far.

[Chryco Psycho]

try leaving the vacuum advance off completely or use an allen wrench inside the vacuum pot & turn it most of the way counterclockwise . your advance curve is too long , you want o be approx 16 * at idle & 36 total

[Budnicks]

Thanks for the direction on this one-I'll need to read up on this one. I've had Holleys for years and this is my first Eddy. I'm not real impressed so far.

Here's a good style QFT HR-Series Vacuum Secondary carb to use in the future, They aren't dirt cheap $380 for the 580cfm, $400 for the 680cfm, $410 for a 780cfm, at Mancini Racing, you can get many different sizes & styles of course, but they are great carbs to begin with, for mild to mid performance builds, very tuneable, fully adjustable, generally trouble free out of the box, the Q Series Douple Pumper Street/Strip Performance carbs are more starting at $630 for a trick 750cfm- $770 for a 1050cfm DP...  I like the suggestion Chryco Pyscho mentioned about the turning in the vacuum advance adjustment, kind of forgot about that adjustment, that is if you have a newer adjustable type vacuum advance, with the allen head adjuster in it...

[billschroeder5842]

Okay, thanks for the advice but it is a bit overwhelming as I'm not a carb tuning guy. I'd like to make what I have work (I'm close to paying off some bills and that takes priority) so I have a few questions:

Timing....how far should I turn the vacuum Allen wrench (counter clockwise) before it it too much?
Should I switch back the vacuum line to the carb side verses the manifold side?
Should I set the accelerator pump on "max squirt" I'm on the lowest or top setting hole now

What do you think?

[greenpigs]

I was always under the impression you use the ported side on a street motor.

Try the middle hole on the pump & test it out & go from there. I would only change one thing at a time so you can tell what is helping or not.

[Cooter]

This car have points Ignition, or Electronic? If points,l throw it in the trash can and get a good Electronic ignition after you figure out the carb.

[billschroeder5842]

Electronic ignition was installed a couple of years ago.
Will do on the "middle" setting.
Thanks for the help!

[elacruze]

It sounds to me like you have a weak spark for some reason. Besides the breakup at RPM, do you have a miss/breakup under high throttle? That is, when you mash the gas does the engine miss, even below 3000rpm? If so, look for a weak coil, poor connections, cross-firing spark plug wires, or carbon tracks in the distributor cap. At larger throttle openings cylinder pressure goes up, plug gap resistance goes up and can force sparks to jump out other places upstream that they're not supposed to. There are a lot of things possible here that are not yet clear, but I don't think your carburetor is the root of your problem. Advancing timing should make things better right up until you get pinging, but also requires higher spark energy. Again this points towards a weak ignition. Verify all your ignition/coil/ballast connections. If they are not perfectly clean, give them a 15 second bath in a solution of vinegar and salt; that will clean contacts. Rinse with water, blow dry and try again.

Also, your pickup coil in the distributor could be getting weak-if it doesn't have a clean strong signal the box will lose track of it with higher RPMs. Mancini told me that many/most stock replacement ignition modules have a threshold right at the limit of the pickup coils. Verify your pickup coil gap, if it's more than about .010" you can narrow it up.

[Chryco Psycho]

Okay, thanks for the advice but it is a bit overwhelming as I'm not a carb tuning guy. I'd like to make what I have work (I'm close to paying off some bills and that takes priority) so I have a few questions:

Timing....how far should I turn the vacuum Allen wrench (counter clockwise) before it it too much?
Should I switch back the vacuum line to the carb side verses the manifold side?
Should I set the accelerator pump on "max squirt" I'm on the lowest or top setting hole now

What do you think?

Youhave approx 14 turns with the allen wrench to play with , I would switch back to carb source for the vacuum line or disconnect it , you probably want to dial most of the advance out to get the short curve you need anyway

[Budnicks]

Okay, thanks for the advice but it is a bit overwhelming as I'm not a carb tuning guy. I'd like to make what I have work (I'm close to paying off some bills and that takes priority) so I have a few questions:

Timing....how far should I turn the vacuum Allen wrench (counter clockwise) before it it too much?
Should I switch back the vacuum line to the carb side verses the manifold side?
Should I set the accelerator pump on "max squirt" I'm on the lowest or top setting hole now

What do you think?

Youhave approx 14 turns with the allen wrench to play with , I would switch back to carb source for the vacuum line or disconnect it , you probably want to dial most of the advance out to get the short curve you need anyway

Like he said above... check your timing at idle first, with the vacuum advance disconnected & plugged at the vacuum source, then check the total advance at like 3000rpm, see what the difference is, you should be able to adjust you vacuum advance to the proper level of advance, it should be in the 16*-20* of initial advance & a total of 36*-38* max with the vacuum advance hooked up, this is what you need final, so no more than 16*-22* of vacuum advance added in {that's the allen screw in the center of the vacuum hole, where the ported vacuum line attaches to the distributor, you will need to turn it in CLOCKWISE to reduce the added vacuum advance timing & COUNTER CLOCKWISE to add vacuum advance timing }, above the initial 16*-20*to  the total timing....

[Chryco Psycho]

do you have a dist handy ?
if you turn the screw counterclockwise the screw unthreads from the diaphragm so it cannot move out with vacuum so CCW reduces the vacuum advance added

[billschroeder5842]

Thank you all-I'm going ot give it a shot tomorrow night; I'm on reserve duty right now so the poor Charger needs to sit 

[billschroeder5842]

**Update**

So I messed with this situation today (I got detoured by a leaky radiator that needed a recore) and I think I improved it, but still have an issue or two...

Initial advanced set to 16-17 and most of the initial bog on take off is gone.
I set the idle at 900 which is about 150 higher than normal but it seems okay; lower doesn't feel "right."
I set the accelerator pump setting on the middle setting, up from the lowest one.

The car is smooth at 3000 with no break up and feels a little quicker. However the timing at 3k seems to read about 50-55 which is way higher than you all recommend. I turned the distributor Allen key about 5 complete turns clockwise but nothing seemed to happen (I'm afraid of going to far and having some screw fall out or something). At 3000 rpm when I punch it, I get this weird fluttering thing happened. No vibration just a flutter with no additional power. When I let up on the gas, everything return to normal.

So, did i not go far enough on the Allen screw?
Could I just screw the adjustment "all the way in" and back off until I get the recommended 36-38 total timing?
Is that flutter thing electronic or lack of gas....I dunno...did jacking with the accelerator pump setting cause this?

Thank you all!!

[resq302]

If you are getting that much advance you may need to adjust the mechanical advance so it stops around 36* total advance.

[billschroeder5842]

I agree on that one but I'm confused...I've read counterclockwise and clockwise to retard the timing (even in this thread) adjustment in the distributor....so can anyone weigh in and clear me up?

Any danger of screwing in/out too much and losing a screw?

Also, I've read several people recommend just blocking off the advance port and just running as mechanical with no vacuum advance, as it will put you "in zone" for timing almost immediately. What are the pros and cons of doing that?

I'm going to mess with this later today--Thanks All!

[Back N Black]

I agree on that one but I'm confused...I've read counterclockwise and clockwise to retard the timing (even in this thread) adjustment in the distributor....so can anyone weigh in and clear me up?

Any danger of screwing in/out too much and losing a screw?

Also, I've read several people recommend just blocking off the advance port and just running as mechanical with no vacuum advance, as it will put you "in zone" for timing almost immediately. What are the pros and cons of doing that?

I'm going to mess with this later today--Thanks All!

I don't use vacuum advance, vacuum advance is mainly for fuel economy.

[Chryco Psycho]

you can turn the scrw out 14 turns , it will not fall out , I would take it a lot further out .
I rarely use vacuum advance either .
I assume this is a big block so advance is clockwise [small block is opposite] , pull the vacuum advance toward the front of the engine .

[billschroeder5842]

So I think I've got it "good nuff"

I messed with the vacuum adjustment for about 30 minutes and could not get any significant change even though I turned the adjustment screw all the way in and all the way out; I still got 55-60 with the vacuum attached at about 2500 rpm. I could only get it to move 500 so I guessing that the distributor is jacked up.

I then adjusted the timing with no vacuum advance attachment to about 17 at idle and increased the engine speed and showed 40-42 degrees at 2500ish. I plug up all the ports and took it for a ride.

*The take off was mostly smooth, much better than yesterday
*I took it up to about 95 mph at about 3800 rpms--everything felt fine, still good power and could have gotten more.
*When I punch it from about 30 mph I get no bog, flutter or hesitation; it seems to accelerate much better.
*When I punch it from a stop it accelerates nicely and "breaks loose" a bit when it shifts into second.
*I put a gauge on the engine manifold side and I get a rock solid reading of 20 when the motor is at 2500 rpms.

So at this point, I'm a believer in "no vacuum advance" as this seemed to solve almost all of my problems. However, I'm looking for the down side...is there anything to watch for if I run the engine with no vacuum advance all the time?

[Back N Black]

So I think I've got it "good nuff"

I messed with the vacuum adjustment for about 30 minutes and could not get any significant change even though I turned the adjustment screw all the way in and all the way out; I still got 55-60 with the vacuum attached at about 2500 rpm. I could only get it to move 500 so I guessing that the distributor is jacked up.

I then adjusted the timing with no vacuum advance attachment to about 17 at idle and increased the engine speed and showed 40-42 degrees at 2500ish. I plug up all the ports and took it for a ride.

*The take off was mostly smooth, much better than yesterday
*I took it up to about 95 mph at about 3800 rpms--everything felt fine, still good power and could have gotten more.
*When I punch it from about 30 mph I get no bog, flutter or hesitation; it seems to accelerate much better.
*When I punch it from a stop it accelerates nicely and "breaks loose" a bit when it shifts into second.
*I put a gauge on the engine manifold side and I get a rock solid reading of 20 when the motor is at 2500 rpms.

So at this point, I'm a believer in "no vacuum advance" as this seemed to solve almost all of my problems. However, I'm looking for the down side...is there anything to watch for if I run the engine with no vacuum advance all the time?

No down side with the vacuum advance disconnected, maybe burn a little more fuel.

[Chryco Psycho]

I agree no problems running with no vacuum long term

[greenpigs]

No down side with the vacuum advance disconnected, maybe burn a little more fuel.

X2