[67gtospud]

Working on getting my 2-4 setup tuned, I installed a Wideband to help me out. They are Edelbrock carbs and I’m looking for suggestions as to what direction I should go. Here’s where I’m at:

(Both carbs are the same setup with progressive linkage)
Primary jets: .086
Secondary jets: .083
Metering rods: .068-.052
Accelerator pump: center hole
Step up springs: 3hg (blue)

Idles at 900rpm with 7hg vacuum.
Idle afr: 14.0
Cruise afr: 13.5-14
Part throttle acceleration: 15-16
Wot afr: ——- (Didn’t get to checking this yet)


My issue right now is under part throttle/mid acceleration the engine is going lean. Which should be working off the primary jets and metering rods but my cruise afr is alright. These are the tuning kits I have: https://www.ebay.com/itm/191763035027

I’m not sure which way I should go to make the change to eliminate the lean condition. Under light driving and cruising the car runs and drives excellent, I just can’t get into the throttle without causing lean detonation so I really haven’t.

[tom s]

Good luck,I have never been able to get the E AFBs to drive well.They seem to race well.What size engine and what size car?Do you have them progressive or solid?Tom

[tom s]

What size CARBs?Tom

[67gtospud]

Originally Posted by tom s

Good luck,I have never been able to get the E AFBs to drive well.They seem to race well.What size engine and what size car?Do you have them progressive or solid?Tom

Engine specs are in signature, running progressive linkage. I’ve had good luck in the past with eddy carbs and typically I find them pretty user friendly; just not sure which direction to go here. Haven’t weighed the car yet with new engine but was around 3650 previously with me, iron headed 400, and full tank of fuel.

[tom s]

Did not what the weight of the car,was asking about the size of the CARBs

[67gtospud]

1403/1404 500cfm carbs.

[Tom Vaught]

His footer Tom says 500 cfm carbs.

Tom V.

[shaker455]

What color Blue is your car?
Fantastic!
When you say progressive linkage just want to verify that it pulls one carb open first?
If you have a primary carb that does all the part throttle then focus on just that one for now.
Do you have the Edelbrock book?
Your car is a stick so go back to:
Stock Orange springs (5" Hg)
drop rod size to .063-.047 in your kit
Test

[tom s]

Finally found it!IMO too small of carbs.Factory 421s used a pair of 625s.Engineers do things for a reason.Tom

[67gtospud]

Originally Posted by shaker455

What color Blue is your car?
Fantastic!
When you say progressive linkage just want to verify that it pulls one carb open first?
If you have a primary carb that does all the part throttle then focus on just that one for now.
Do you have the Edelbrock book?
Your car is a stick so go back to:
Stock Orange springs (5" Hg)
drop rod size to .063-.047 in your kit
Test

That blue is Fords Bright Atlantic Blue Metallic. There’s a lot of pearl in it and I don’t think it’s the same shade in any picture I have.

Yes, the rear carb is the primary and operates before the front carb. My lean condition come in as the secondary’s of the primary carb open and the primary’s of the secondary carb open. If I accelerate on the primary throttle blades of the primary carb only afr is around 13.0 and alright. It seems to be as soon as the second carb starts opening.


With the orange springs the metering rods were dancing up and down at idle. I tried the 4”hg springs and they still danced some. (That was at 5”hg engine vacuum whereas I got it up to 7 so I may try the 4”hg springs.

Won’t the .063-.047 cause my cruise to be too rich?

[shaker455]

I think a guy @ work with a 2019 Ford tuck has that color....figures!...lol
Thanks, I have a better picture of what you have.
If your secondary's open before it pulls the the secondary carb then may jet up the rear on primary carb...BUT.. rods are the easiest to change without popping the top off so I would say try the rods first.

Your springs if accurate should be 1.5" to 2"Hg below your vac number .

How were you able to detect the springs bouncing?

[67gtospud]

Originally Posted by shaker455

I think a guy @ work with a 2019 Ford tuck has that color....figures!...lol
Thanks, I have a better picture of what you have.
If your secondary's open before it pulls the the secondary carb then may jet up the rear on primary carb...BUT.. rods are the easiest to change without popping the top off so I would say try the rods first.

I’ll try the rod change and see what happens. Is it an issue to have a large split in the metering rod steps such as .068-.047. The factory 2-4 calibration had rod steps of .065-.057.

[shaker455]

Give it a try Tyler,
It's about what works for you, don't worry about factory specs as they are not here tuning to your engines requirements..
Jeff

[Kenth]

I have found the angle of the air valves too steep in these carbs letting too much air in too fast. Works for a little CSB, not so good for B O P engines.
Very hard if not impossible to cure by rejetting.
You may find and use weights from original Pontiac AFB´s or cut the E-clone weights for reduced angle on the air valves making them sit more flat/closed in the bore.

[Tom Vaught]

Originally Posted by Kenth

I have found the angle of the air valves too steep in these carbs letting too much air in too fast. Works for a little CSB, not so good for B O P engines.
Very hard if not impossible to cure by rejetting.
You may find and use weights from original Pontiac AFB´s or cut the E-clone weights for reduced angle on the air valves making them sit more flat/closed in the bore.

Jon Hargrove and I have also discussed this weakness with the E-Carbs.
The proper air valve calibration cannot be understated.

Tom V.

[67gtospud]

Let me just make sure I understand this: So grinding a small amount off the bottom of the weight will allow the secondary valve to sit flatter therefore slightly delaying air intake and help eliminate a lean spot?

My lean condition is barely into the secondaries of the primary carb and at the same time the primaries of the secondary carb are opening. How much airflow does it take to open the secondary air valve?

[61-63]

The secondary air valve has nothing to do with part throttle or cruising afr, they come into play only as the carb transitions from two barrels into all four barrels easing the transition so the car doesn't fall on its nose.

What does your afr meter show when you floor it and open all eight holes up? And does the car fall on it's nose and/or hesitate for a half second or second when you floor it? You mention above getting detonation under part throttle acceleration are you really getting detonation or just seeing a leaner mixture on your afr meter? FYI the sd dual quads had .009 or so split on the metering rods from the factory.
If it is true that the secondary air valve on the primary carb if beginning to open as the primary throttle plates on the secondary carb are starting to open, and this is occurring during what you refer to as "part throttle/mid acceleration" then you have your linkage adjusted incorrectly. Adjust it so you can operate at cruising speed on only the front two holes on the primary carb. then slightly beyond that the other six holes should open. up almost simultaneously. You may have to fabricate something to allow your linkage to do that, Finally you want the car to idle off of both carbs not just the rear carb. If your afr is ok at cruising you should not have to mess with jets you should be able to fix this by adjusting the linkage and switching metering rods.

[Tom Vaught]

Originally Posted by 67gtospud

................... How much airflow does it take to open the secondary air valve?

That is a question that cannot be easily answered.
For a given application, to get that answer might take a bunch of road testing for your engine/vehicle combination. Just because the carburetor has a crude "airflow sensing" device on the secondaries does not mean that it is correct for all configurations in a single carb application (and you are doing a dual carb application).

But what some have done in the past is to drill some holes in the counterweights of the air valves. .125" hole seems to work well with some slightly larger lead shot.

So you (for example) drill 5 holes in each counterweight along the outer edge of the weight. So now you have changed the ability of airflow to open the air valve connected to each pair of counterweights. It should be easier for the weights to move to an open position. You will probably get a hesitation in the WOT performance doing this mod initially.

So you then add a couple of pieces of lead shot to the counterweight.
One piece of lead shot to each counterweight then you drive the car again.

Still have the hesitation, add a second piece of shot to the second hole in each counterweight. Drive the car again. Did the hesitation go away?
If so you are done. If not, then add a third piece of shot to each counterweight, and test again. At some point the hesitation will disappear.
So at that point you have the carbs secondary air valves calibrated for THAT ENGINE COMBINATION. Change the engine combination and you need to verify that the previous combination is still good or needs additional mods.

Carb Engineers used to have access to lots of counterweights and could grab several of different counter weight vs air flow calibrations.
Then it was a easy swap to find the correct one for that engine combination.
You do not have that luxury, so you use the lead shot method.

Tom V.

[67gtospud]

Originally Posted by 61-63

The secondary air valve has nothing to do with part throttle or cruising afr, they come into play only as the carb transitions from two barrels into all four barrels easing the transition so the car doesn't fall on its nose.

What does your afr meter show when you floor it and open all eight holes up? And does the car fall on it's nose and/or hesitate for a half second or second when you floor it? You mention above getting detonation under part throttle acceleration are you really getting detonation or just seeing a leaner mixture on your afr meter? FYI the sd dual quads had .009 or so split on the metering rods from the factory.
If it is true that the secondary air valve on the primary carb if beginning to open as the primary throttle plates on the secondary carb are starting to open, and this is occurring during what you refer to as "part throttle/mid acceleration" then you have your linkage adjusted incorrectly. Adjust it so you can operate at cruising speed on only the front two holes on the primary carb. then slightly beyond that the other six holes should open. up almost simultaneously. You may have to fabricate something to allow your linkage to do that, Finally you want the car to idle off of both carbs not just the rear carb. If your afr is ok at cruising you should not have to mess with jets you should be able to fix this by adjusting the linkage and switching metering rods.

When I floor it, afr jumps up to 15-16 for a second then drops to 10-11 at WOT (which is still a bit rich). The car falls on its nose when the afr jumps up. Under mid throttle when the afr leans out the engine stumbles and detonates.

I can bring the car up to speed slowly and cruise without issue on only the 2-barrels of the primary carb, afr stays around 13.5-14.0. The lean condition occurs as the 4 more barrels tip in (6 total opening). So I believe my linkage is all set correctly and operating as it should.

I do have both carbs synced so the engine idles off both equally

[67gtospud]

Originally Posted by Tom Vaught

That is a question that cannot be easily answered.
For a given application, to get that answer might take a bunch of road testing for your engine/vehicle combination. Just because the carburetor has a crude "airflow sensing" device on the secondaries does not mean that it is correct for all configurations in a single carb application (and you are doing a dual carb application).

But what some have done in the past is to drill some holes in the counterweights of the air valves. .125" hole seems to work well with some slightly larger lead shot.

So you (for example) drill 5 holes in each counterweight along the outer edge of the weight. So now you have changed the ability of airflow to open the air valve connected to each pair of counterweights. It should be easier for the weights to move to an open position. You will probably get a hesitation in the WOT performance doing this mod initially.

So you then add a couple of pieces of lead shot to the counterweight.
One piece of lead shot to each counterweight then you drive the car again.

Still have the hesitation, add a second piece of shot to the second hole in each counterweight. Drive the car again. Did the hesitation go away?
If so you are done. If not, then add a third piece of shot to each counterweight, and test again. At some point the hesitation will disappear.
So at that point you have the carbs secondary air valves calibrated for THAT ENGINE COMBINATION. Change the engine combination and you need to verify that the previous combination is still good or needs additional mods.

Carb Engineers used to have access to lots of counterweights and could grab several of different counter weight vs air flow calibrations.
Then it was a easy swap to find the correct one for that engine combination.
You do not have that luxury, so you use the lead shot method.

Tom V.

Interesting. How is the lead shot retained in the holes? Also do you happen to have a picture to go off of? I really don’t feel this is the main source of my lean condition however may be a contributing factor and I can dial it into my engine combo.

I’m sure I could run larger carbs on my engine; however I feel I can and would prefer to get it running well with what I have.