setting up dual quad tips&tricks
#1269184
07/17/12 12:17 AM
07/17/12 12:17 AM
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Joined: Feb 2007
Posts: 649
Davis, California, USA
MrBelvedere2
OP
mopar
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OP
mopar
Joined: Feb 2007
Posts: 649
Davis, California, USA
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Hey guys, I just got my dual edelbrock 500 cfm carbs on my 383. They were tested each after a rebuild on the single 4bbl manifold, and worked great. I put my offenhauser manifold on, and mounted the carbs, running a 1:1 linkage (non-progessive). I fired it up and it wants to idle very high, timing was set with a single carb right where the engine likes. It acts like a vacuum leak, and it does run hot as well. I tried playing with them (idle adjust, mixture, etc.) while the engine is running but to no avail. The idle screws were all the way out. Any tips to get them tuned up and to sync together? I retarded the timing which brought the idle down but not sure the engine will like it that retarded. thanks for any help.
1965 Plymouth Belvedere II hardtop
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Re: setting up dual quad tips&tricks
[Re: MrBelvedere2]
#1269185
07/17/12 01:39 PM
07/17/12 01:39 PM
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Joined: Dec 2005
Posts: 799
Missouri
bb74swngr
mopar addict
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mopar addict
Joined: Dec 2005
Posts: 799
Missouri
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Hey Larry. Is there a reason why you are not using progressive linkage? I have a dual setup with Eddy instead Offy intake, progressive linkage. Seems like it would be difficult to get the idle circuits happy on two carbs at the same time. Could you unhook one of the carbs and try to tune it that way first. The other carb butterflies would have to be completely closed while tuning. Just a thought...
BigBlock 74 Swinger
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Re: setting up dual quad tips&tricks
[Re: dynamite]
#1269188
07/17/12 03:41 PM
07/17/12 03:41 PM
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Joined: Jul 2006
Posts: 4,179
California
mickm
master
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master
Joined: Jul 2006
Posts: 4,179
California
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i agree, it sounds like a vacuum leak. fix that first.
and if the manifold gives even distribution from the rear carb, i'd run progressive linkage as well. run off the idle circuit on the rear carb, and have the front butterflies all the way closed and the idle screws all the way in. that way you kick in to the cruise circuit and the WOT.
if you don't go progressive:
i have this vacuum tool, i can't remember the name, i'll find it later, that is meant for tuning multiple carbs on one of the foreign models, (can't remember which one either!). i took a 100 count CD case, and cut a hole in the top the same size as the base of this vacuum tool. i plop the CD case over the air horn of the carb, and the tool on top, and then i can read the vacuum that carb is pulling. that way i can set the throttle plate openings evenly on both carbs. works nice and is very quick.
i'll try to remember to get the name of that thing, or PM me if i don't respond back. busy couple days ahead of me!
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Re: setting up dual quad tips&tricks
[Re: mickm]
#1269189
07/19/12 10:55 AM
07/19/12 10:55 AM
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Joined: Feb 2007
Posts: 649
Davis, California, USA
MrBelvedere2
OP
mopar
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OP
mopar
Joined: Feb 2007
Posts: 649
Davis, California, USA
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Thank you for the replies so far very helpful. I was wondering this as well.
I had the manifold powder coated clear, but they did not mask off the intake suface and ports or the carb mounting surfaces. Even though they are smooth and I used gasket sealer, could this be where it could be leaking vacuum?
1965 Plymouth Belvedere II hardtop
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Re: setting up dual quad tips&tricks
[Re: MrBelvedere2]
#1269190
07/19/12 02:46 PM
07/19/12 02:46 PM
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Joined: Aug 2003
Posts: 43,173
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,173
Bend,OR USA
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Quote:
Thank you for the replies so far very helpful. I was wondering this as well.
I had the manifold powder coated clear, but they did not mask off the intake suface and ports or the carb mounting surfaces. Even though they are smooth and I used gasket sealer, could this be where it could be leaking vacuum?
Take the intake and valley pan off of the motor, clean all of the gasket surfaces real well and lay the intake on the heads, move it around to see where it wants to lay. Once you have it where it seems to be happy take a feeler gauge and check all the corners, top and bottom on all four sides and write down what fits where, IE left front lower is .015, left front top is .003, left rear lower is .000, left rear top is.022 and so on. Once you have that recorded take the intake to a good machine shop and give them the measurements and have them machine square so it will fit your motor properly  I like to the have the bottoms at .000 and the tops opened up a tiny bit, say .001 to .003 so the manifold will squish the gasket tight at the bottom, sealing it up real well I like to use the Fel Pro paper gaskets on both sides of the valley pan also 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: setting up dual quad tips&tricks
[Re: Cab_Burge]
#1269191
07/19/12 10:43 PM
07/19/12 10:43 PM
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Joined: Feb 2007
Posts: 649
Davis, California, USA
MrBelvedere2
OP
mopar
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OP
mopar
Joined: Feb 2007
Posts: 649
Davis, California, USA
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Yes I did make sure the surfaces were clean and I am using the paper gaskets as well as a new valley pan. I'm just wondering since the mating surface is powdercoated it could be causing it to leak?
1965 Plymouth Belvedere II hardtop
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Re: setting up dual quad tips&tricks
[Re: mickm]
#1269192
07/19/12 10:46 PM
07/19/12 10:46 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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Quote:
i have this vacuum tool, i can't remember the name, i'll find it later, that is meant for tuning multiple carbs on one of the foreign models, (can't remember which one either!). i took a 100 count CD case, and cut a hole in the top the same size as the base of this vacuum tool. i plop the CD case over the air horn of the carb, and the tool on top, and then i can read the vacuum that carb is pulling. that way i can set the throttle plate openings evenly on both carbs. works nice and is very quick.
i'll try to remember to get the name of that thing, or PM me if i don't respond back. busy couple days ahead of me!
It's called a carb synchronizer, used them on my multicarb motorcycles
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: setting up dual quad tips&tricks
[Re: Supercuda]
#1269196
07/20/12 01:25 PM
07/20/12 01:25 PM
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Joined: Oct 2007
Posts: 1,973
SoCal
jake4cars
top fuel
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top fuel
Joined: Oct 2007
Posts: 1,973
SoCal
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Quote:
Quote:
i have this vacuum tool, i can't remember the name, i'll find it later, that is meant for tuning multiple carbs on one of the foreign models, (can't remember which one either!). i took a 100 count CD case, and cut a hole in the top the same size as the base of this vacuum tool. i plop the CD case over the air horn of the carb, and the tool on top, and then i can read the vacuum that carb is pulling. that way i can set the throttle plate openings evenly on both carbs. works nice and is very quick.
i'll try to remember to get the name of that thing, or PM me if i don't respond back. busy couple days ahead of me!
It's called a carb synchronizer, used them on my multicarb motorcycles
Dan Dvorak at Dvorak racing in Florida sells them, they work great!
Joey
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Re: setting up dual quad tips&tricks
[Re: jake4cars]
#1269197
07/20/12 08:14 PM
07/20/12 08:14 PM
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Joined: Jan 2003
Posts: 1,436
Oklahoma City OK
Cudajon
pro stock
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pro stock
Joined: Jan 2003
Posts: 1,436
Oklahoma City OK
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Sounds like a vacuum leak OK, but before you go tearing it apart. Close the front carb all the way down so that it is running off the rear carb only. Make sure the idle screw is all the way out so the butterflys are closed down for sure. Might disconnect the linkage to the front carb so you don't start fighting the front carb while adjusting the rear carb. Trying to sync both carbs to idle is very frustrating and requires work with the springs and metering rods. Thats why progressive is SO much better. It takes a lot of engine to handle two carbs on straight linkage and be streetable. The fact it is overheating is also an indication of a lean condition. I find a wide range O2 sensor to be a lot more valuable than a carb synchronizer for adjusting multiple carbs. It will tell you if your lean.
Last edited by Cudajon; 07/20/12 08:28 PM.
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