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Thread: Dual Carbs on 320 with Dynaflow - Bad Idea?

  1. #1
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    Dual Carbs on 320 with Dynaflow - Bad Idea?

    I have an Edmunds dual carb manifold and always figured I would put it on my 1949 Roadmaster Sedanette with the 320 ci engine and Dynaflow transmission. I mentioned this to a mechanic who does alot of mid 60's V-8 builds and he scoffed, saying it would only serve to make the engine bog down. I think he said it would be a problem due to vacuum and the automatic transmission. I would ask the mechanic more but he's condescending and I hate dealing with him.

    Anyone actually done this or have advice, comments?

  2. #2
    I would ask the mechanic more but he's condescending and I hate dealing with him.


    i can't comment on anything else, but that sounds like a REALLY unhealthy relationship to have with someone whom you are spending a lot of money with.

    dual carb will pull less vacuum at WOT but below 3/4 throttle i wouldn't think it should be a problem?
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
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  3. #3

    Duel carbs.

    Sorry the mechanic is so misinformed. Buick came with duel carbs available in 1941- 1942.

    Ben

  4. #4
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    Quote Originally Posted by bob k. mando View Post
    I would ask the mechanic more but he's condescending and I hate dealing with him.


    i can't comment on anything else, but that sounds like a REALLY unhealthy relationship to have with someone whom you are spending a lot of money with.

    dual carb will pull less vacuum at WOT but below 3/4 throttle i wouldn't think it should be a problem?
    Ha, fortunately he is just a mechanic and not my mechanic. He rebuilt a carb for me once and that's as far as I want to go with the man.

    But I myself am certainly no mechanic and do not understand the vacuum issue you are referring to, Bob. The Dynaflow is a real slow starter as it is. Winds up and up and finally takes off. Slowly. So, I don't need to impair any kind of take off speed. It's a ***** backing out of a driveway into a busy street and trying to get out of the way of oncoming traffic with a Dynaflow transmission. So, does he have a point? Anyone actually done this set up?

    As to the duals being on the Buicks in earlier years, they never were paired with the automatic Dynaflow, right?

  5. #5
    $0.02 worth...

    I wouldn't think twice, I would run the dual carbs. They should have a progressive linkage and should not be any problem.

    If your car is not running well, you may only compound your problems by modifying things before correcting them. Be sure your engine and transmission are up to standards. Do a compression test, check the ignition system is all operating correctly (mechanical advance).

    Is the transmission up to par? If you could find at least one other similar car to have a ride in, that you knew was in good condition, you might be able to compare it to yours. Then you might notice the two cars performance is similar (good), or the other cars engine or transmission performs much differently than yours (bad). This might give you a direction to go in.


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  6. #6
    But I myself am certainly no mechanic and do not understand the vacuum issue you are referring to, Bob.


    at WOT the butterflies are wide open so the only practical restriction on air intake is going to be the throat size of the carb. obviously, two carbs are typically going to flow a LOT more air than a single carb unless you got some monstrous huge 4 barrel or two teeny tiny little things ( in which case, what's the point? ).

    this WOT will create max vacuum behind the air filter BUT is also min vacuum *in the manifold*, which is below the carb(s). low vacuum under the carb means it doesn't pull air through the carb like you might want it too.

    it also means that you can get ahead of the venturi effect and actually lean the mix out. this is the reason for booster pumps on the carb in order to physically actuate a fuel shot in order to keep the engine from stumbling / stalling under accell.

    balancing all this stuff with a single carb can be a chore. balancing TWO carbs can be a huge pain in the ***.




    The Dynaflow is a real slow starter as it is.


    the Dynaflow is notoriously NOT a 'performance' transmission. you can probably get rolling better by starting out in Low but wiki says that this can be hard on the trans.

    https://en.wikipedia.org/wiki/Dynaflow

    i would do as Bob suggests though and see if you can find someone to compare your car too. or just have yours gone through and refurbished.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  7. #7


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  8. #8
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    With the first Dynaflow coming out on '48 models, it was never used with Compound Carburetion.

    Buick went almost to the proposed setup with the '52 Roadmaster. It had 1- 4bbl carb, 320 L8, and Dynaflow. A '52 service bulletin introducing the 4bbl makes comparisons back to the '41-42 compound setup. The '51 and '52 Roadmaster Dynaflows are essentially identical--meaning no tweaking was needed to handle the increased carburetion.

    HP increased 12% although the compression ratio was raised some at the same time. Dynaflows in those and earlier years had no throttle linkage connections or vacuum connections to cause concern. Dynaflows afterward handled ever-increasing HP every year into the nailhead V8 era.

    The change from '40 to '41 with the introduction of Compound Carburetion gave a 17% increase in HP. The compression ratio was raised here also, even more than from '51 to '52. Adding the 2- 2bbl setup to the '49 should give something like 12-14% more HP since the compression ratio is not changing.

    To evaluate vehicle performance there are gas mileage tests taken at several steady speeds (30/50/70) available in the shop manuals. As to acceleration, Consumer Reports 25 years ago did a tongue-in-cheek comparison test of the '92 vs. '52 Roadmasters. 0 to 60 time for the '52 was 15.5 sec. Gas mileage at a steady 55 mph was 15. That agrees well with the shop manual figure of 15.8 at a steady 50. Mileage dropped to 8 mpg on their city-driving test.

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