2carb40

Putzing with 1941-42 dual carb parts

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14 minutes ago, valk said:

That's what my rear damper looks like - valves and counter weight removed. Told the damper was obsolete given today's modern fuel. 

 

I think we've found the source of your excessive fuel flow in the rear cylinders...

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Posted (edited)

I agree with Matt.  I don't understand what modern fuel has to do with it.  Based on how my car runs, I would advise you to put the damper back in unless you are going to convert to a different system like Lawrence did.

Edited by neil morse (see edit history)

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20 hours ago, Jack Worstell said:

I recall reading somewhere that  dual carbs were standard in 1941 except that they were optional on series 40

and that in 1942 dual carbs were standard on all series.

 

Is this info correct  ?

 

Jack Worstell

 

I do not have a Buick Master Parts book, however:

 

Carter listed 551s as a single carb for 1942 only for the series 40 and 50

Carter listed 549s as a single carb for 1942 only for the series 60, 70, and 90

Stromberg listed 7-66 as a single carb for 1942 only for the 40 series

Stromberg listed 7-57 as a single carb for 1942 only for the 60, 70, and 90 series

 

Jon.

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Posted (edited)

Quote Valk "That's what my rear damper looks like - valves and counter weight removed. Told the damper was obsolete given today's modern fuel. "

 

Modern fuel should have nothing to do with determining whether or not to use the damper.

 

If an original set-up, with the "dumper" rear carb, and progressive linkage - use the damper.

If the set-up has been converted to two "complete" carbs (the "dumper" carb is not complete), and straight linkage - the damper should not be used.

 

Have NEVER experimented with the original set-up (dumper, progressive) without the damper, so GUESSING!

 

I would expect, ASSUMING THE REAR CARB AND THE PROGRESSIVE LINKAGE ARE CORRECTLY ADJUSTED, that the system would run lean, not rich. Most newer, V-8 engines with multiple carbs had a lockout to prevent the secondary carbs from opening before a certain RPM, thus flooding the engine with air and creating a lean condition.

 

Jon.

Edited by carbking (see edit history)

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The engine can only use as much fuel/air mixture as developed vacuum will allow. You could stand on the gas pedal of my 58 Pont with stock tri-power at low rpm and it was a pig. At about 35 mph the engine rpms were high enuff to provide enuff vacuum to handle the full throttle position better and acceration was then much more impressive. 

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Here is a picture of the bottom of the throttle body of a Compound Carburetion rear carb:

 

 

http://www.thecarburetorshop.com/Buick_rear_TB.JPG

 

Note the presence of idle mixture screws.

 

The rear carb was not a "complete" carburetor. The rear carb has an idle circuit, and a main metering circuit. It does not have a choke circuit, a pump circuit, or a power circuit.

 

The two existing circuits work exactly as they would in a complete carburetor.

 

Stromberg suggests an idle mixture setting of approximately 1 turn on EACH of the two carbs.

 

Note that the throttle plates are designed to completely close. Thus, ASSUMING that the carburetor is correctly adjusted, and the progressive linkage is correctly adjusted, NO FUEL would flow through the main circuit with the damper removed, UNTIL the progressive linkage was opened sufficiently far to allow the throttle blades to open. After the throttle blades started to open, fuel would flow proportionally to the air velocity through the main venturii.

 

The damper assembly is in place, not to prevent overfueling, rather to prevent (or minimze) a significant hesitation because of an instantaneous lean condition if the rear (secondary) carburetor is opened before the engine RPM is sufficient to accept the additional AIR.

 

If the damper is NOT present, fuel flow still would not start from the rear carb until such time as the progressive linkage actually opened the rear carb throttle blades.

 

Jon.

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Posted (edited)

What he said! Vacuum sucks dont it? Some smarties call that negative presure. Litrally, not figuratively speaking!

Edited by 2carb40 (see edit history)

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