Got the "Edel-bog?" Just fixed mine finally. - Vintage Mustang Forums
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post #1 of 24 (permalink) Old 12-06-2015, 03:19 PM Thread Starter
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Got the "Edel-bog?" Just fixed mine finally.

I've been living with the infamous "Edel-bog" for a while. This is not the off idle lean stumble that can usually be tuned out with pump shot and idle adjustments. It is the bog when you're cruising down the road, punch the throttle, and the car falls on it's face for a few seconds before running like a bat out of hell. The mechanical secondaries open, then the air flap above them opens a split second later when the engine is supposedly flowing enough fuel through the boosters, and ready for the additional air flow/volume. A/F ratios have been monitored using a wide band gauge, and a major lean issue occurs for me at that transition.

My combo breathes really well, and also has strong vacuum signal when cruising, so it creates a situation where a secondary bog is likely. I have a 3,200 stall, it revs REALLY quickly, and what would really be the best solution is a double pumper. However, I'm a cheap SOB, and I knew this problem was solvable. I found that by disconnecting the secondaries, my bog went away completely. So, here's what I did:

TUNING
All manner of springs, rods, jets, etc. have been tried at METICULOUSLY SMALL intervals, and I have driven the heck out of the car in between changes, documenting the differences. The car runs absolutely flawless except for that transition, which is why I have invested the time to try and make it work. I love Edelbrock carbs, and can speak from lots of experience with both Holley style and Edelbrock/Carter style. The only real issue with Eddy's is that damn bog. My AFR is 14:1 at idle, 14.5:1 cruise and 12:1 WOT. The car absolutely fries the 20" tires from a stop, but I get an off-the-charts lean stumble when I mash the throttle from cruising speed. This concerns me because I have converted the carb for blow through, and I plan to use it with the Paxton 1200 in my garage soon. Last thing I need is a carb that goes lean under boost at 4,000 RPM!

1. First, I knew that if I could slow down the opening of the air door enough, I could eliminate the bog. So I drilled out large holes in the counterweights, melted lead into the to create slugs, and then epoxied them a little for insurance. I added about a half ounce in total weight, and didn't really have any more area I could drill to add more. This improved the bog, but not nearly enough.

2. Next, I used baling wire, and created some nice little restrictors to place into the air bleeds on the secondary clusters. The idea was to cut out the air from the hight speed air bleeds and fatten up the transition mixture. Helped a little, but hurt drivability some too. Removed them.

3. Finally, I opened up an old Carter manual I had in my library, and went to the "if you absolutely have to" tab I had on the page, and did as instructed: I pulled the secondary clusters out, and on the bottom there are 2 brass tubes. The large one is the emulsion tube , and the small one is a secondary emulsion tube which is restricts too much fuel from reaching the transfer slots below the air door too soon. Unfortunately, that is exactly WRONG for a performance application with these carbs. Heavy breathing engines need that extra fuel immediately at the secondary transition. So, I mounted the clusters in a vice, and gently gripped the small tube with vice grips, and tapped it out on each side with a small hammer. They weren't damaged, so I can replace them if need be.

Took it for a drive. In second gear, 3,800 RPM I floored it—incredible power, and NO BOG! I did notice the needle on the AFR gauge spike to 16:1 for a quick second, but it wasn't enough to create the bog. If I'm at a lower RPM, I do still get a slight bog. I may be able to tune that one out now with some spring/rod experimentation. May run a little richer on the primary/cruise mode so I have more fuel flowing from the beginning.

Anyway, thought this might be helpful.


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post #2 of 24 (permalink) Old 12-06-2015, 03:28 PM
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interesting, that's something to keep in mind for future use
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post #3 of 24 (permalink) Old 12-06-2015, 03:48 PM
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You will be wasting your time with the Edlebrock or any other vacuum secondary carb used in conjunction with the Paxton.


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post #4 of 24 (permalink) Old 12-06-2015, 03:53 PM
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This solution to the Edelbrock tuning issue has always worked for me....

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post #5 of 24 (permalink) Old 12-06-2015, 04:03 PM
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In my experience, you will never realize anywhere close to the full potential of the Paxton induction with ANY vacuum secondary carb. Most the guys running Paxtons on their GT350's have found this out, and have ditched the Autolite 600, or Holley 715 that was originally used (with different float bowls than the stock LeMans bowls).
If you put a wideband air/fuel ratio meter on the car, you will immediately see why the vacuum carbs are a poor choice. The performance is very inconsistent due to the secondaries opening inconsistantly.

A 650 Holley Street HP works very well, and when used with an air diffuser, the high rpm performance is very consistent. I made my diffuser from a marine spark arrestor. And they come without a choke air horn, so you don't have that to have to mill off.










Z


Last edited by zray; 12-06-2015 at 04:06 PM.
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post #6 of 24 (permalink) Old 12-06-2015, 04:11 PM Thread Starter
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Originally Posted by zray View Post
You will be wasting your time with the Edlebrock or any other vacuum secondary carb used in conjunction with the Paxton.

Z
Sorry buddy, have to call you on this one. First, Edelbrock secondaries are manual. Air door above opens with vacuum but that is not a "secondary" throttle plate. Second, Carter/Edelbrock were used in factory Paxton blow through applications for years. See Studebaker Avanti.

You are mistaken.
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post #7 of 24 (permalink) Old 12-06-2015, 04:16 PM Thread Starter
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Originally Posted by zray View Post
In my experience, you will never realize anywhere close to the full potential of the Paxton induction with ANY vacuum secondary carb. Most the guys running Paxtons on their GT350's have found this out, and have ditched the Autolite 600, or Holley 715 that was originally used (with different float bowls than the stock LeMans bowls).
If you put a wideband air/fuel ratio meter on the car, you will immediately see why the vacuum carbs are a poor choice. The performance is very inconsistent due to the secondaries opening inconsistantly.

A 650 Holley Street HP works very well, and when used with an air diffuser, the high rpm performance is very consistent. I made my diffuser from a marine spark arrestor. And they come without a choke air horn, so you don't have that to have to mill off.l


Z
I do run a wide band, as I mentioned. It's way easier to throw more money at this to solve it. I would prefer to use the edelbrock but if I have to spend hundreds on a carb, it will be a Mighty Demon 650 Blow Thru with an Extreme Velocity carb hat.

Thanks for the info though. Cool diffuser idea.

Last edited by vegascarnut; 12-06-2015 at 04:19 PM.
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post #8 of 24 (permalink) Old 12-06-2015, 05:03 PM
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Originally Posted by bartl View Post
This solution to the Edelbrock tuning issue has always worked for me....

I've been fighting the same issues with my '68 GTS Dart 340...I'm heading to Holley soon....very soon....

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post #9 of 24 (permalink) Old 12-06-2015, 07:40 PM
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Originally Posted by bartl View Post
This solution to the Edelbrock tuning issue has always worked for me....

+1000000

I'm never going to waste my money on an edelbrock carburetor again. They make good intakes, that's all I'll use from them.


The holley is great, or better yet look into a quickfuel. Glad you fixed your bogging issues though.

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post #10 of 24 (permalink) Old 12-06-2015, 08:21 PM
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Originally Posted by vegascarnut View Post
Sorry buddy, have to call you on this one. First, Edelbrock secondaries are manual. Air door above opens with vacuum but that is not a "secondary" throttle plate. Second, Carter/Edelbrock were used in factory Paxton blow through applications for years. See Studebaker Avanti.

You are mistaken.
But it doesn' t have a secondary accelerator circuit/pump. So it is asking for bog . . . right from the engineering of it. Allows the rears to open manually and don't supply the band-aide squirt of fuel, until the power circuit cuts in.
post #11 of 24 (permalink) Old 12-06-2015, 08:30 PM
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This solution to the Edelbrock tuning issue has always worked for me....

Absolutely
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post #12 of 24 (permalink) Old 12-06-2015, 08:38 PM
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Quote:
Originally Posted by vegascarnut View Post
Sorry buddy, have to call you on this one. First, Edelbrock secondaries are manual. Air door above opens with vacuum but that is not a "secondary" throttle plate. Second, Carter/Edelbrock were used in factory Paxton blow through applications for years. See Studebaker Avanti.

You are mistaken.
Gotta call you on this one, too. Edelbrock/AFB secondary throttle plates ARE manual, but the air door ISN'T vacuum, it's opened based on air VELOCITY. In addition, the opening of the air door is directly linked to lifting the metering rods in the secondary metering jets, providing instant fuel enrichment IF the air door is adjusted correctly, that is.

The reason a Holley or other mechanical secondary carb needs a secondary accelerator pump squirt is because of the sudden rush of air through the venturis before fuel is drawn up and out of the boosters.

Bart

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post #13 of 24 (permalink) Old 12-06-2015, 09:36 PM
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Why not call the guys that do it for a living?

Blow-Thru Carburetors

Pro Systems - Blow Through Carburetor

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Patrick
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post #14 of 24 (permalink) Old 12-06-2015, 09:50 PM
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I rest my case.

Edlebrock's make for a lousy carb when used with a Paxton. I don't know of anyone who is relying on one of them. Why fight sucess, go with a proven solution and be done with it.

Z

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post #15 of 24 (permalink) Old 12-06-2015, 10:02 PM Thread Starter
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Gotta call you on this one, too. Edelbrock/AFB secondary throttle plates ARE manual, but the air door ISN'T vacuum, it's opened based on air VELOCITY. In addition, the opening of the air door is directly linked to lifting the metering rods in the secondary metering jets, providing instant fuel enrichment IF the air door is adjusted correctly, that is.

The reason a Holley or other mechanical secondary carb needs a secondary accelerator pump squirt is because of the sudden rush of air through the venturis before fuel is drawn up and out of the boosters.
The air door is opened by air velocity, yes, BUT it isn't connected to anything. It is absolutely independent of the rods--it just sits there and flops back and forth in "the breeze" with a counterweight.

You are confusing AVS carbs with Performer carbs. AVS is adjustable but they won't work with a blower because of that spring loaded air flap.
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