Columbia 2 Speed - Vacuum

mgm60

mgm60

Member
Installing a Columbia 2 Speed in my 36 which has dual Stromberg 97s. Have the carb adapter plate with vacuum port but what do I do with the second carb to keep them at the same height? Use a spacer or use a second adapter plate? If I use a second adapter plate should I just block the vacuum port or plumb it inline with the first? Not a lot of room between the two carbs on my Sharp intake to be able to connect the second vacuum port if its needed.
 
I didn't want to poke a hole in my Eddie Meyer intake so I just drilled through the center of one of the studs holding the carb. to the intake. I was afraid it would be too restrictive a source for vacuum but it has been working for 30 + years now.
 
Do both of the Carbs, have to be at the same height? Check your vacuum gauge and I believe you will find about 15 which should work to shift the Columbia but is getting low. So make sure the Columbia is in gear when you shift.
 
Vacuum Tanks and one-way valves: Do any of you guys add an extra vacuum reservoir/tank with a one-way "flapper" valve to store more vacuum?
 
On my 35, equipped with twin carbs like original poster, I have included a non return valve in the vacuum line to columbia control. Dunno if it's needed, but figured it can't hurt.
 
A little bit of trying to re-invent the wheel..
The engine in my '36 is a 59AB that is highly modified, with dual 97's on a Offy Super manifold. The rear axle under my car is a 47-48 Columbia with '47-48 electric over vacuum controls.
The vacuum source for my Columbia is via a port in the manifold below the rear carb. I installed a tee fitting into the the manifold, attached the vacuum line to the wipers on one side of the tee and the vacuum line to the electric solenoid OD valve on the other side of the tee.
This system has been working since 1955 with no difficulties.
I have no idea how many inches of vacuum the engine has, I figure, if it ain't broken, don't fix it.
 

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blucar said:
A little bit of trying to re-invent the wheel..
The engine in my '36 is a 59AB that is highly modified, with dual 97's on a Offy Super manifold. The rear axle under my car is a 47-48 Columbia with '47-48 electric over vacuum controls.
The vacuum source for my Columbia is via a port in the manifold below the rear carb. I installed a tee fitting into the the manifold, attached the vacuum line to the wipers on one side of the tee and the vacuum line to the electric solenoid OD valve on the other side of the tee.
This system has been working since 1955 with no difficulties.
I have no idea how many inches of vacuum the engine has, I figure, if it ain't broken, don't fix it.
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516589


516590
 
When you shift the Columbia the dash control vents to atmosphere one side of the shift canister and applies vacuum to the other side. The dash valve reverses this action to shift to the opposite ratio so be careful where you install a one way valve. I don't think any are necessary. As mentioned previous the reduced vacuum when using dual carburetors is usually substantial enough to shift.
 
Terry said:
When you shift the Columbia the dash control vents to atmosphere one side of the shift canister and applies vacuum to the other side. The dash valve reverses this action to shift to the opposite ratio so be careful where you install a one way valve. I don't think any are necessary. As mentioned previous the reduced vacuum when using dual carburetors is usually substantial enough to shift.
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Good point! One would have to ensure that any sort of vacuum storage would be between the engine and the controller valve - such that all the control sees is more/better vacuum.
 
Hell, Even with a blower, mine pulls in and out without hesitation. The outlet is between the carburetor bases and the rotors. You have to let off the gas like all Columbia's to have the vacuum rise.
 
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