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So on lars favorite carb I dont know anything about edlebrock. If you were to use two of them that were not the 500 cfm they recommend for there two 4 intake. I would assume they would need the amount of idle fuel lowered in them. So how do you do that. I'm pretty sure lars wont give out any details on his most coveted brand of carb.
It does not matter what size it is......the idle circuit is the same. Adjust as you would any other idle mixture....with a vacuum gauge. On a two four setup, I would start with all four screws 3/4 of a turn out. Adjust in 1/8 turn increments jumping around the screws until you reach the highest vacuum......you may have to play around a bit to get all four screws the same but this is important as you are distributing idle fuel at two ends of the intake.
Are you using a progressive linkage that pulls the back carb fist as Edebrock designed? If not......if you are using a 1 to 1 linkage.....it is CRITCAL to get the front and back carb as close as possible to throttle blade opening BEFORE you do the mixture screws. Symmetry is your friend here in this case......like syncing carbs on a bike.
I will also add that the difference between the low rise C3B dual quad intake and the taller Performer RPM dual quad intake on a mild to warm small block is about 25 horsepower.......the original C3B intake was patterned after the 265 Duel Quad intake and is all done flowing at about 325 horsepower or so.
Jebby
Last edited by Jebbysan; Mar 25, 2020 at 07:37 AM.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Little Mouse
So on lars favorite carb I dont know anything about edlebrock. If you were to use two of them that were not the 500 cfm they recommend for there two 4 intake. I would assume they would need the amount of idle fuel lowered in them. So how do you do that. I'm pretty sure lars wont give out any details on his most coveted brand of carb.
That's pretty funny... my reputation precedes me...
As Jebby states, the idle mixture will not be affected - each carb will need to be set up exactly as it would be by itself, and the idle mixture screws will end up being set roughly the same. I usually start all 4 at 1 turn out so I know they're rich, and then start turning each one in 1/4 turn at a time. Eventually, fine setup will be in 1/8 turn increments, and you'll likely end up with all 4 in the 1/2 to 7/8 turn range. What you will find is that the idle speed screws may need to be lowered down just a tad, since the engine will be getting idle air from both carbs. Again, the key is as Jebby states: Symmetry. Keep both carbs set up exactly the same. All 4 mixture screws should end up in the same position, and the idle throttle blade openings on both carbs needs to be exactly the same.
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
Originally Posted by lars
That's pretty funny... my reputation precedes me...
As Jebby states, the idle mixture will not be affected - each carb will need to be set up exactly as it would be by itself, and the idle mixture screws will end up being set roughly the same. I usually start all 4 at 1 turn out so I know they're rich, and then start turning each one in 1/4 turn at a time. Eventually, fine setup will be in 1/8 turn increments, and you'll likely end up with all 4 in the 1/2 to 7/8 turn range. What you will find is that the idle speed screws may need to be lowered down just a tad, since the engine will be getting idle air from both carbs. Again, the key is as Jebby states: Symmetry. Keep both carbs set up exactly the same. All 4 mixture screws should end up in the same position, and the idle throttle blade openings on both carbs needs to be exactly the same.
That's pretty funny... my reputation precedes me...
As Jebby states, the idle mixture will not be affected - each carb will need to be set up exactly as it would be by itself, and the idle mixture screws will end up being set roughly the same. I usually start all 4 at 1 turn out so I know they're rich, and then start turning each one in 1/4 turn at a time. Eventually, fine setup will be in 1/8 turn increments, and you'll likely end up with all 4 in the 1/2 to 7/8 turn range. What you will find is that the idle speed screws may need to be lowered down just a tad, since the engine will be getting idle air from both carbs. Again, the key is as Jebby states: Symmetry. Keep both carbs set up exactly the same. All 4 mixture screws should end up in the same position, and the idle throttle blade openings on both carbs needs to be exactly the same.
Lars
have seen this chinese made speedmaster intake manifold it's called a pod I'm going to go down to summit in arlington take a look at it. it's not a dual plane and the carb bases are spread out better directly over the intake on the head. I'd bet two of the shorter fuel bowl vacuum secondary I think they were called 1650 series holleys could be used on it or for sure any holley mounted sideways would work. On the 47 series double pumpers I had they were set up so rich on the idle intended for big cams people would do everything from drill holes in the throttle blades to stick wire in the fuel port to drill out the idle air bleed. I cant figure this out maybe it's the cheap cost or lars has told everyone how great edlebrock carbs are, but everywhere I look some car has an edelbrock carb on it. I just thought with two carbs the idle fuel could get rediculous and how would you fix an edlbrock if needed. I'm considering if I do it trying two of there new latest poop anular boosted just in the primary AVS-2 carbs. The damn Holley's I would like to have are expensive and I have to buy two. I do have two old 4780 DPs 800cfm I could use that are free except kiting them. Lol would be damn big on the tiny sbc I'm going to use and the manifold more like a tunnel ram. Not even close to a duel plane.
Last edited by Little Mouse; Mar 25, 2020 at 12:42 PM.
From: At my Bar drinking and wrenching in Lafayette Colorado
Here's a dual quad setup I have for a Pontiac - I have tested it, and it runs just great with the Holley idle mixture screws in their "normal" positions. Air/fuel mixture at idle can be nailed down easily right at 14.6:1 in the normal adjustment range, and no throttle plate drilling or other mods are required to the stock-configured carbs (these are the Holley 390's, limiting total airflow to a street-friendly 780 cfm). This setup is done with 1:1 linkage, and actually works just great:
I see quick fuel has die cast carbs I can afford 650 dps all the adjustments of the high dollar carbs around $385.00. I'll mount them sideways.
Terrible idea.......you will have the idle circuit and primaries over off to one side of the intake......only works in Pro Stock or Blower application.......
Just get two 600cfm single feed Holleys.......el cheapo entry level classic Holley.
It works on tunnel rams but I can put them length wise with a little finesse. I'm betting Lars put that picture of two holleys on there to keep me from going over to the dark side with edelbrock carbs' supprised it was not two Q-Jets.
I had an old I think ofenhauser intake that took 2 quadrajets. I don't remember what it fit. I picked it up a swap meet probably 40 years ago as a joke. Got lots of laughs with it
Vacuum secondary would be nice, but holley pretty modular should be able to just turn them sideways and make the linkage 1 to 1. Not about to turn them sideways and not do that. That's basically same way the 660 center squirter got used a lot. Great carbs wish I had two them.
Last edited by Little Mouse; Mar 25, 2020 at 10:27 PM.
I had an old I think ofenhauser intake that took 2 quadrajets. I don't remember what it fit. I picked it up a swap meet probably 40 years ago as a joke. Got lots of laughs with it
hey dont laugh offenhauser still sells that one new. You can get away with anything on a duel plane. But I think that one is 360 has 4 cylinders on each side being fed by each side of the carbs. If you had a single plane one carb manifold put a divider down the middle. You would have basically the same thing. Lol
Last edited by Little Mouse; Mar 25, 2020 at 10:40 PM.
Eddy carb idle.
