Thread: progressive dual quads.

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Hi all,,

I just got the dual quad set up for my 350 (edelbrock), my question is when setting up in a progressive manner is it better to turn the idel mixure screws the same on bolth carbs, or is it better to set the rear carb as a primary and just use the front carbs idel mixture screws to ensure front cylinders are not running lean, So it would be 2 turns on rear screws 1/2 on front carb screws. i keep getting different answers when i call the manufactuer and i dont want to hurt the motor. Any suggestions?

With the AFB dual quads I had many moons ago, the front carb did not have idle screws, and the rear carb acted as the primary where you adjusted the idle. The front carb did not function until the progressive linkage activated it.

Originally Posted by rumrumm

With the AFB dual quads I had many moons ago, the front carb did not have idle screws, and the rear carb acted as the primary where you adjusted the idle. The front carb did not function until the progressive linkage activated it.

Rumrumm, do you think that helped the dual quad - cough, cough - MPG?

That was back in 1969-71 when gas was 28 cents per gallon. Gas mileage? I didn't need no stinkin' gas mileage! LOL!

Dean, did you get your vacuum problem solved? Haven't heard back from you about it. Just curious why the thread of dual carbs when there was a problem to be solved. C'mon, inquiring minds want to know...

almost. it was just running realy lean on the rear carb. Placed my hand on the carb to cover primaries and it smooth out a lot had slight stumble and the idel picked up, i adjusted the idel mix screws to 2 turns out on the rear carb and 1/2 on the front and it runs mutch better vacuum almost totaly steady 18 inches, but now i noticed one of the front squirters is dripping (hence the stumble ) but only when running, checked the floats and needle and seat , same thing, reduced fuel presure to 3 psi (just a test) and still dripping shut motor off and the drip stops instantly, fuel pressure does not drop stays where set. i have no idea, any suggestions?

P.S. thanks for all your help so far, you guys are great !!!!

Holleys or Edelbrock (carters)? Double check the check ball for the squirter. It should stop the drip. If not, you possibly have a gasket not seated in the right position between the body and top aloowing syphon backand creating a venturi effect. Holley's are slightly different because of design but same symptoms.

edelbrocks, where is the check ball ? do i have to remove the carb or just take of the top to get to it ?

Originally Posted by Dean C.

edelbrocks, where is the check ball ? do i have to remove the carb or just take of the top to get to it ?

It's underneath the primary squirters.

after 2 days of thrying to fix this problem, edelbrock told me to send them the carb they think somthing is cracked, we will se when i get thte new one how it runs.. thanks guys

Originally Posted by Dean C.

after 2 days of thrying to fix this problem, edelbrock told me to send them the carb they think somthing is cracked, we will se when i get thte new one how it runs.. thanks guys

Just wondering if you ever got the 2x4 running, I would also like to ask this, is the 2x4 you are playing with on the air gap intake and which 4 is primary front or rear?

Hi all sorry i have not gotten back sooner small computer problem then i could not log back on,, anyways, i got the 2 4's working pretty good. very slight stumble at idel just needs a fine tune after motor breaks in. almost done i attached pics of car let me know what ya think.

Nice looking car!
I always like more than one carb!

Pat

Thanks, It is a 1936 plymouth 5 window
i have one question i just bouht a carb tuning dvd because they siad they showed how to tune 2 4's but it did not. so i e mailed the company on the dvd and asked them this is what they said.

I REALLY don't recommend running any kind of progressive linkage between the front and rear carbs on any twin carb set-up. Progressive linkage is great for six pack set ups where one CENTER carb runs the engine evenly up until half throttle, then the outer two carbs come-in later on (progressivly) for full throttle pulling.

Setting a front or a rear carb up as progressive can make the front or rear of the engine run lean, depending on which one comes in later. I would highly recommend running both carbs in perfect sync with each other.

Adjusting the idle mixture screws a bit more on the rich side for one of the carbs will only cause it to run slightly richer during, and right off an idle, but not at part throttle or while under normal acceleration. Under normal driving conditions, you are pulling from the main jets, NOT the idle mixture circuits that the screws adjust. They call them IDLE mixture screws for a reason :-)

Does progressive linkage work? Yes, but as I said.... IF there is a center carb to run the engine EVENLY, and 2 outer carbs that come-in progressivly as you get into the throttle. It is not good for your engine to have one carb running at part throttle while the other is closed. Make them both the same or you're asking for engine damage.

Have a good one,
Arron

Now i am nervuse i don't want to cause any damage to the motor, any suggestions?

Thanks Denny
this is the best pic i can get of the linkage, i'm just worries that i should be set up 1:1 insted of progressive.