Engine runs better on only primary carb

[Poppas409]

I have a 62 bubbletop 409 2x4. When I bought the car it had the stock afb carbs, ran terrible, got them rebuilt, still no oomph. Bought new edelbrocks and linkage, ran runs better but revs slow, driving it the other day the linkage came apart, where the barrel fittings hold rod to secondary carb, drove home on primary carb only. What a difference, it runs so much better, responds faster, revs faster. I have tried both ways of installing the linkage, 1to 1 and progressive. It ran better the progressive way. Obviously getting too much fuel using both carbs, how do I get the best results using both carbs. Thanks for the help

 

[wristpin]

Youve answered your own question....less fuel. Get a book or go online and find how to adjust for change idle, intermediate and wide open positions.

 

[RussC]

Check needle and seats...floats on the front carb

 

[boxerdog]

Okay, it runs great on the back carb. Now set it up to run only on the front carb and see if the problem tracks to that carb alone.

 

[427John]

Do you know the specs on the engine, compression, cam, heads?I mean I could see this happening if someone installed a stock jetted 2x4 setup on a stock 340hp 409.A dual quad setup would work on a 340hp motor but would require recalibrating the carbs.

 

[Poppas409]

It’s the 409/409. Running on just the front carb to try is also a good idea. Compression is 175 or so all the way around. I think the problem is the linkage, I guessing adjust it o secondary carb doesn’t open until primary carb is almost full throttle? I bought the edelbrock link because I thought it would be easier to adjust but the barrel nut on the secondary rod has a habit of coming loose no matter how tight I get it. Maybe locktite is the answer.

 

[Jim Sullivan]

I'm using the Edelbrock linkage and never had an issue. We did have a bad float in a relatively new Edelbrock carb a few years ago.

 

[our1962]

https://show-cars.com/product/3057

I used the attached link, linkage for my edelbrock carbs and everything worked fine.

The only thing, I had too do was drill the carbs were the linkage connects as the linkage is one size bigger than the edelbrock carbs.

 

[Gofish]

Help me out - 1) do the 409/409 dual quads use a progressive linkage, 2) does the front carb have idle circuits, etc. or not?

Not trying to steal your thread, trying to learn.

John

 

[scott hall]

Yes on progressive from factory. No idle circuit for front carb.

 

[427John]

Is there a possibility that the carbs are swapped position wise?

 

[boxerdog]

They are Edelbrocks, not the original AFBs; shouldn't matter?

 

[pvs409]

Here is the factory 409 2-4 linkage on my Dual Edelbrock 1406 carbs (530 HP with 482 cubic inches ) -very fast
we changed the springs and jets that came in the Edelbrocks made it much faster

 

[wristpin]

Youve answered your own question....less fuel. Get a book or go online and find how to adjust for change idle, intermediate and wide open positions.

Ive never quoted myself before!!
Dont forget that accelerator pump circuit. An accelerator pump set where its always drooling or squirting will make any other adjustments moot.

 

[our1962]

@Poppas409, we like pictures of all 1962 Bubbletops post some

 

[427John]

They are Edelbrocks, not the original AFBs; shouldn't matter?

I finally got that and also realized he was saying it ran fine only on the primary,at first I was thinking he said it ran fine on just the secondary.My dyslexia is acting up again.

 

[tenxal]

Here is the factory 409 2-4 linkage on my Dual Edelbrock 1406 carbs (530 HP with 482 cubic inches ) -very fast. We changed the springs and jets that came in the Edelbrocks made it much faster

How quick does it run?

 

[Poppas409]

Pvs409. Excellent pictures, I assume the linkage is progressive? Do you prefer the stock linkage over the edelbrock? I will post some pictures when I take some bettter ones. Did everyone see the March of 2020 issue of Car Craft where the guy bought Dyno Dons 62 and put an LS motor in it...I don’t understand why you would do that. beautiful car, but not the same.

 

[pvs409]

Yes the linkage is progressive, and it’s easy to adjust, fits better and easier to fit than Edelbrock linkage.

My 530 HP 409 runs 13.70’s 105mph in the 1/4 mile with street tires and without a big 9“ rear end. I don’t drag race it regularly.
Its scary in first and 2nd gear.

 

[Poppas409]

I’m still working on my carb issue, am ordering new linkage from Showcars that says it will fit Edelbrock carbs. I like Pvs409 setup, at what rpm does your secondary carb start to open? I have the Edelbrock linkage now set at 1to1, direct, it’s too herky jerky to drive on the street, if I was racing it would be fine.