383 dual quads lean at idle and cruise

[Moparpuller]

I have a 68 dart 383 with an offy dual quad and a pair of avs2 650s. I have been playing with the vacuum gauge and mixture screws to get the highest vacuum. Will get them set and my afr gauge reads 12-13 at idle on both banks. I go drive it and the right bank will go lean will cruising. Up into the 15-16 range and you can hear it lean pop out the exhaust. Come back to an idle and the right bank will still idle lean and not be matched close to the left bank anymore. Wide open is good. Actually rich and both sides read about the same. Any help would be appreciated. Thanks grant

 

[like_A_pike]

vacuum advance hooked up? Ported or manifold source?

 

[Moparpuller]

vacuum advance hooked up? Ported or manifold source?

Not hooked up yet. Was getting all my base settings done first before I tackled the vacuum advance

 

[TT5.9mag]

I dont know them very well first hand, but some of those early dual quad manifolds are well known for having very bad distribution problems. I sure hope you can tune around it.

 

[Moparpuller]

I dont know them very well first hand, but some of those early dual quad manifolds are well known for having very bad distribution problems. I sure hope you can tune around it.

Thanks. Yeah this is my first experience with them. It has a divider straight down the manifold dividing the 2 banks. It’s not a true dual plane. The carb adapters are also divided. I thought about cutting the divider out on them. I do have a Weiand 8008 single carb manifold if I can’t get these figured out

 

[TT5.9mag]

Thanks. Yeah this is my first experience with them. It has a divider straight down the manifold dividing the 2 banks. It’s not a true dual plane. The carb adapters are also divided. I thought about cutting the divider out on them. I do have a Weiand 8008 single carb manifold if I can’t get these figured out

I would try just about everything I could in the carbs before I started cutting on the intake. And if I got to that point I’d do a bunch of research looking for what others have done on that specific intake first. There are a handful of threads (I was searching for you) on those 650avs2 carbs and it seems off idle lean is a thing. The cure is most definitely in the idle circuit and transition tuning. In this one below, pay attention to anything written by “tuner”

Edelbrock 650 AVS2 going super lean at part throttle - Don Terrill’s Speed-Talk

 

[Moparpuller]

I would try just about everything I could in the carbs before I started cutting on the intake. And if I got to that point I’d do a bunch of research looking for what others have done on that specific intake first. There are a handful of threads (I was searching for you) on those 650avs2 carbs and it seems off idle lean is a thing. The cure is most definitely in the idle circuit and transition tuning. In this one below, pay attention to anything written by “tuner”

Edelbrock 650 AVS2 going super lean at part throttle - Don Terrill’s Speed-Talk

Thanks for that. I will mess with it more tonight

 

[matthon]

Fwiw the Weiand tunnel ram is exceptional.
I've run it on a 383 with 390s and 600s, 1:1 linkage.

I'm no carb expert, so listening to the smarter than me folks above is a good bet.

Captain Obvious here, for single, the Performer RPM is the best.
I ran that Weiand 8008 and it was ok.

 

[mygasser]

you could check what difference removing the dividers in the intake would make by just fitting open spacers under the carbs.
neil.

 

[Moparpuller]

Fwiw the Weiand tunnel ram is exceptional.
I've run it on a 383 with 390s and 600s, 1:1 linkage.

I'm no carb expert, so listening to the smarter than me folks above is a good bet.

Captain Obvious here, for single, the Performer RPM is the best.
I ran that Weiand 8008 and it was ok.

I have thought about a tunnel ram. Just would like to be able to keep everything under a small scoop. Something like a Hemi hood. Not sticking clear out. I will also try just open spacers under the carbs. Thanks

 

[Killer6]

Before pulling Your hair out, I'd check all 4 float levels, can't fix that with tuning.....

 

[Moparpuller]

May have found my problem. Took the carbs apart last night. Found a small amount of debris and a metering rod with a bent tip. Waiting on a rebuild kit and calibration kits to show up now. Thanks for all the help

 

[TT5.9mag]

May have found my problem. Took the carbs apart last night. Found a small amount of debris and a metering rod with a bent tip. Waiting on a rebuild kit and calibration kits to show up now. Thanks for all the help

Huh. Fingers crossed for you that solves the problem. Did the carb come out of the box with a bent metering rod?

 

[Moparpuller]

Huh. Fingers crossed for you that solves the problem. Did the carb come out of the box with a bent metering rod?

It was used. I just hadn’t noticed it before

 

[perfacar]

might have to stagger jet also, and rejet , depends just food for thought

 

[perfacar]

12 to 13 afr at idle is kinda rich, thats usually at wide open throttle, my afr doesn't read at idle, usually at 17 18

 

[perfacar]

on any dual four , the rear carb is main one, the front carb, isn't used for idle,.

 

[mygasser]

on any dual four , the rear carb is main one, the front carb, isn't used for idle,.

on a factory dual quad setup with progressive linkage, yes. i wouldn't say so on a tunnel ram though as they normally have the carbs opening together.
neil.

 

[Moparpuller]

on any dual four , the rear carb is main one, the front carb, isn't used for idle,.

Thanks I will look in stagger jetting if this doesn’t fix it. The rest of my parts should be here today. Also linkage is 1-1 not progressive. I have been adjusting the carbs with the linkage disconnected and adjusting the idle down equally between the carbs and then centering the linkage when done

 

[nutz]

Would think if they are the same
Swap the carbs and see if it changes to other bank
Maybe intake leaking
Vacuum booster or too much pcv

 

[MOPARMAGA]

I just ran into an issue with a customer, dude didn't have his carb gasket lined up with the manifold lol

 

[Moparpuller]

I just ran into an issue with a customer, dude didn't have his carb gasket lined up with the manifold lol

Gaskets are all lined up. Getting ready to go out and button it up and see how it acts

 

[j par]

Thanks I will look in stagger jetting if this doesn’t fix it. The rest of my parts should be here today. Also linkage is 1-1 not progressive. I have been adjusting the carbs with the linkage disconnected and adjusting the idle down equally between the carbs and then centering the linkage when done

So this is the avenue that I was going down tuning my dual quads.. a lot of the research I did when I was in your same boots led me to tuning the carbs slightly different... at first I was on that whole, make everything equal thought process and drove the car with each carburetor and then linked the two of them together..., I've done 1 to 1 linkage and progressive and ran them that way for sometimes figuring things out and I did end up 1 to 1, and I did end up tuning the carburetors and the idle primary circuits, different, but had the same secondary jets, because when everything's wide open, it's all white, open..... I think what really convinced me that
Tuning them slightly different. It came from when I looked at if you ordered a brand new set of edelbrock( dual quad) carburetors, they had different jets and metering rad or springs or metering rod in each of the carburetors from the factory...
This manifold issue, though, I have no idea whatsoever. I use a #1995 dual quad. edelbrock from summit.
Check out my thread called "tunnel ram Tuesday"..
I bet you could tag a couple members from that thread and get some help or actually tag these two threads together, then probably help a lot of people as well....

Remember, everybody loves a tunnel ram...

 

[Rug_Trucker]

Thanks. Yeah this is my first experience with them. It has a divider straight down the manifold dividing the 2 banks. It’s not a true dual plane.

Offenhauser has never built a dual plane manifold. They wouldn't call it a 360* if it was. I have a small block Dual Port. 2 runners per cylinder. Primaries have their own smaller runners, secondaries have their own bigger runners. It's 2 single planes in one.

 

[nutz]

Had one on a amc 390