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2x Weber Vacuum Pickup ?

M

Mike snyder

Donation Time
I am installing duel Weber carbs on my Alpine. I am going to run a vacuum advance distributer. Should I:
1. Tap a vacuum pick up port into a single intake runner?
2. open a single vacuum pick up port on a single weber?
3. Open both vacuum ports on the Webers and tie them together and then run them to the distributer?

The distributer has been specially built for the mods I have done on this engine. Let me know your thoughts.
Thanks,
Mike Snyder
 
R

RootesRacer

Donation Time
No one does this.

When running twin webers, you wont have enough manifold vacuum to operate the vacuum advance, and any ports your carbs may have wont be correct for the advance unit anyway (I assume your intake is not DCOE since DCOEs dont ever have advance porting).

Recurve your dizzy for full mechanical and move on.
 
alpine_64

alpine_64

Donation Time
Mike,

Did you buy the zenith manifold that had been modded to accept 2 x DGV style webers? If so, that is a different setup to the sidedraft scenario.

Those of us that went DCOE's move to mechanical dizzys.. its probably best you do the same.

If you want to look at comprable dual DD setups.. check out the aftermarket triumph TR4 DD setups and see if they se vacuum and if so how.
 
R

RootesRacer

Donation Time
alpine_64 said:
Mike,

Did you buy the zenith manifold that had been modded to accept 2 x DGV style webers? If so, that is a different setup to the sidedraft scenario.

Those of us that went DCOE's move to mechanical dizzys.. its probably best you do the same.

If you want to look at comprable dual DD setups.. check out the aftermarket triumph TR4 DD setups and see if they se vacuum and if so how.
Click to expand...

If memory serves, he has the one off intake with twin DCNF carbs, which are not progressive like the DVG.
Main reason you cant use any of the port signals is becuase with that many butterflies opening all at once, the manifold vacuum is already gone before you are off of the progression holes (which are used as the vacuum porting).
You wont get much vacuum from the ports, and definitely not when you need it which is under cruising conditions...
 
M

Mike snyder

Donation Time
Well this sounds like bad news... I've got DCOE 40's. Is there a way to boost the vacuum signal or covert a vacuum dizzy to mechanical? Sadly, I already had the dizzy rebuilt/recurved.
 
alpine_64

alpine_64

Donation Time
Jarrid,

Thanks for jogging my memory as tho which carbs.. they are the similar type used on the fiat dino v6?

Mike.. would love to see how you went setting up the linkages and some pics of the setup in the engine bay.
 
R

RootesRacer

Donation Time
Mike snyder said:
Well this sounds like bad news... I've got DCOE 40's. Is there a way to boost the vacuum signal or covert a vacuum dizzy to mechanical? Sadly, I already had the dizzy rebuilt/recurved.
Click to expand...

I am confused.

40 DCOEs dont have vacuum ports.
40DCNF do.

Are yours sidedraughts or downdraughts?

No way to boost the signal (practically speaking).

Dizzy needs recurved so it has less total advance so the low speed running advance has more timing there when set to max timing at high RPM.
 
M

Mike snyder

Donation Time
40 DCOE's don't have a vacuum port but there is a plug covering a vacuum access port and you can pick up a small kit to attach a vacuum line to the carb.
I had the dizzy rebuilt by Advanced Distributors and he did an amazing job. I am going to give him a call on Monday and see what are his suggestions. I am running a custom header and I have no clearance problems so I will be using a Weber LP-4000 bottom mount linkage.
Mike
 
R

RootesRacer

Donation Time
Mike snyder said:
40 DCOE's don't have a vacuum port but there is a plug covering a vacuum access port and you can pick up a small kit to attach a vacuum line to the carb.
I had the dizzy rebuilt by Advanced Distributors and he did an amazing job. I am going to give him a call on Monday and see what are his suggestions. I am running a custom header and I have no clearance problems so I will be using a Weber LP-4000 bottom mount linkage.
Mike
Click to expand...

The plug is to cover the machining of the progression holes.
They sometimes are used to connect to manometers for synchronization but they are NOT intended to be used for vacuum advance as the pneumatics of the connected tubing would interfere with the progression fueling.

Carbs that have advance ports use a separate set of progression holes (often quite different size and shape) than those used by the light running circuit.
 
M

Mike snyder

Donation Time
Good news. I talked to Advanced Distributors and he said it is 15 minutes of work and I can use the same dizzy without the vacuum hooked up and get the proper results. One more mail off to the shop and I am back on track.
Mike
 
R

RootesRacer

Donation Time
Be sure he doesnt just change out the springs and weights.

The advance stops need changed or modified so you have less advance range from idle to max mech advance.
When I setup my dizzy, I had to do some welding to limit the mech timing range from 26 degrees to 18.
As far as I know lucas never made 9 degree (cam) advance spindles for the 25D dizzy.

YMMV
 
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