383 dual quads lean at idle and cruise

[fishmens67]

my afr doesn't read at idle, usually at 17 18

That's about where I'm at

 

[Moparpuller]

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....View attachment 1716448387
Remember, everybody loves a tunnel ram...

Thanks. I didn’t have much time to mess with it today. Will update when I get back to it

 

[str12-340]

Moparpuller - please post some photos of your set up. Considering an in line dual quad set up on a 383.

 

[Moparpuller]

Moparpuller - please post some photos of your set up. Considering an in line dual quad set up on a 383.

Sorry just saw this. I will tomorrow. Was able to mess with it more tonight. I have gotten it balanced pretty good at idle. Cruising is still an issue. If I run at around 3,000 it runs really smooth and and the afrs are pretty close. If I let off the throttle much they get a big spread between the 2 and it will start running rough till I bring the rpm back up

 

[Newbomb Turk]

Sorry just saw this. I will tomorrow. Was able to mess with it more tonight. I have gotten it balanced pretty good at idle. Cruising is still an issue. If I run at around 3,000 it runs really smooth and and the afrs are pretty close. If I let off the throttle much they get a big spread between the 2 and it will start running rough till I bring the rpm back up

You can’t be fine to tune the carbs until both carbs are flowing the same amount of air at idle. You will never get it right.

You need a Unisync. You can find them on Amazon for pretty cheap.

Then you need a plastic (or aluminum if you prefer) carb hat.

You put a hole in the carb hat and seal the unisync to the hat.

Get the engine warm and idling at the speed you want. Unhook the throttle linkage so that the carbs are not hooked together.

Out the unisync on the carb, whichever one you want and adjust the airflow on the meter so the float in the tube is centered or close to it. Note exactly where it is.

Put the unisync on the other carb and read the meter. If it’s higher than the other carb, you need to close the throttle on that carb until it’s close.

Then go back and fourth between the carbs until the idle speed is what you want and both carbs are reading the same airflow on the meter.

Then you can hook the throttle linkage up and don’t touch the curb idle screws. Make the linkage hook to the carb, not the other way around.

The you can work with your air/fuel mixture screws.

 

[Moparpuller]

You can’t be fine to tune the carbs until both carbs are flowing the same amount of air at idle. You will never get it right.

You need a Unisync. You can find them on Amazon for pretty cheap.

Then you need a plastic (or aluminum if you prefer) carb hat.

You put a hole in the carb hat and seal the unisync to the hat.

Get the engine warm and idling at the speed you want. Unhook the throttle linkage so that the carbs are not hooked together.

Out the unisync on the carb, whichever one you want and adjust the airflow on the meter so the float in the tube is centered or close to it. Note exactly where it is.

Put the unisync on the other carb and read the meter. If it’s higher than the other carb, you need to close the throttle on that carb until it’s close.

Then go back and fourth between the carbs until the idle speed is what you want and both carbs are reading the same airflow on the meter.

Then you can hook the throttle linkage up and don’t touch the curb idle screws. Make the linkage hook to the carb, not the other way around.

The you can work with your air/fuel mixture screws.

Ok. Thank you. I got them ordered and should have them Saturday. Same principal as syncing motorcycle carbs I assume

 

[Newbomb Turk]

Ok. Thank you. I got them ordered and should have them Saturday. Same principal as syncing motorcycle carbs I assume

Yes sir. Exactly the same.

 

[Moparpuller]

Yes sir. Exactly the same.

Thanks. I will report back when I have that done

 

[Moparpuller]

Thanks. I will report back when I have that done

Was able to mess with it over the weekend and it still didn’t want to act right. I believe fuel may be puddling on the intake floor messing with things. It was pretty wet when I took it off. I ended up putting my Weiand single on it so I can drive it. Will probly bolt it back on in the spring and revisit the issue. Thanks for all the help

 

[PRH]

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’m not a fan of the 360* Offy manifolds in general.

I’d try a couple of open carb spacers so the two sides can both pull off all the carb circuits.

And when you get tired of messing with that, put an RPM on it.

 

[Moparpuller]

I’m not a fan of the 360* Offy manifolds in general.

I’d try a couple of open carb spacers so the two sides can both pull off all the carb circuits.

And when you get tired of messing with that, put an RPM on it.

I put my Weiand 8008 on it for now. With one of the ede 650s. Will probly end up getting a Holley 750vs Photo attached for the guy that wanted to see what it looked like

 

[Moparpuller]

Put the intake back on with 1 inch open spacers. Went and drove it after setting everything. Same thing. Above 28-3000 everything is happy. Under that and it starts getting lean on the left side and missing

 

[MOPAROFFICIAL]

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.

I think that was their version of a good Street rod manifold. Going for that high velocity intake charge

 

[Killer6]

Put the intake back on with 1 inch open spacers. Went and drove it after setting everything. Same thing. Above 28-3000 everything is happy. Under that and it starts getting lean on the left side and missing

Ever consider You've got a low-speed ignition misfire? If there's a carbon track in the cap near 1-3-5-or7, and the rotor tip is in proximity moreso closer to base timing, it could be jumping past the tower post. Misfire shows up lean, lots of unburned fuel, may pop &/or act like it's flooding. Is it an erratic misfire?
Otherwise, how did the intake gaskets appear? It does sound like a Dr.side vacuum leak, or plugged idle circuit, but these are some other things to check out.
Peace.

 

[Moparpuller]

Put the intake back on with 1 inch open spacers. Went and drove it after setting everything. Same thing. Above 28-3000 everything

Ever consider You've got a low-speed ignition misfire? If there's a carbon track in the cap near 1-3-5-or7, and the rotor tip is in proximity moreso closer to base timing, it could be jumping past the tower post. Misfire shows up lean, lots of unburned fuel, may pop &/or act like it's flooding. Is it an erratic misfire?
Otherwise, how did the intake gaskets appear? It does sound like a Dr.side vacuum leak, or plugged idle circuit, but these are some other things to check out.
Peace.

its not a hard miss you can just tell it’s not happy. Gaskets are all good. I’ve replaced them every time I’ve had it apart just to be sure have sprayed and checked for leaks. The thing is it doesn’t do it with the single carb Weiand 8008 intake. I have ran it and swapped both carbs to it to eliminate a carb issure

 

[MOPAROFFICIAL]

Just curious, what pump cam and shooters, pv rating?
35, 37...?

 

[MOPAROFFICIAL]

Dual 500's would be better for drivability.

 

[Killer6]

Put the intake back on with 1 inch open spacers. Went and drove it after setting everything. Same thing. Above 28-3000 everything

its not a hard miss you can just tell it’s not happy. Gaskets are all good. I’ve replaced them every time I’ve had it apart just to be sure have sprayed and checked for leaks. The thing is it doesn’t do it with the single carb Weiand 8008 intake. I have ran it and swapped both carbs to it to eliminate a carb issure

I meant to ask You how the float levels all checked out when You had them apart, with dual carbs, the part throttle can be sensitive to a low fuel level.

 

[Bewy]

Probably a fue/jetl distribution issue. Every dual 4bbl intake that I have seen where jetting was provided, the jetting would be staggered. Cannot remember seeing a jetting schedule where all 8 barrels had the same jets.

 

[Bewy]

1962 383, factory duel 4 bbl.
- all pri jets 0.089"
- met rods #81 front carb [ 070/067 ]. Rear carb#192 rod [ 081/045 ]
- sec jets: 067 front carb. 055 rear carb.

Note the huge differences: 067 for full power on the met rod, front carb, 045 on rear carb.

 

[Rug_Trucker]

I think that was their version of a good Street rod manifold. Going for that high velocity intake charge

It was out when Edelbrock had their SP2P economy/mpg manifold. (sold that to Tony Defeo) Mine was for the 318 as they quit making the 340/360 version. I bought it for torque, economy in my '79 Maxivan work truck. It worked good up to 5200rpm with the Comp RV cam.

 

[Ricks70Duster340]

It was out when Edelbrock had their SP2P economy/mpg manifold. (sold that to Tony Defeo) Mine was for the 318 as they quit making the 340/360 version. I bought it for torque, economy in my '79 Maxivan work truck. It worked good up to 5200rpm with the Comp RV cam.

Yes! I had the SP2P intake, RV cam, and 600 Holley carb on a 318 in my 69 Charger in 1980. Drove from San Antonio to Oakland CA and got over 20 mpg!

 

[PRH]

The thing is it doesn’t do it with the single carb Weiand 8008 intake.

Done!
Close the hood and enjoy!!

 

[Moparpuller]

Yup. That’s happening tonight after work

Done!
Close the hood and enjoy!!

 

[CRUZE 418]

Moparpuller, you are not that far from me, I'm just north of you by Muscatine. I have finally figured out my Sixpack problem. After reading through this thread, I am not looking forward to the day when I get my Hemi running. Edelbrock carbs and intake. Looking forward to it running, just not the tuning part! Next year.
Best of luck!