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.
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.
