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SIze of carbs for the R4 motor

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  • SIze of carbs for the R4 motor

    Hi readers. About 18 months ago I bought a 1961 Lark VIII convertible with an R4 motor and a 4-speed transmission. Wait, wait, I know that's not real, but that's how it was advertised in TW, and it turns out it's sort of right ... or at least OK.
    It's a car originally from Richmond VA, and that spent most of its time in Fredericksburg VA. The info I got from the man I bought it from led me to the car's builder, with whom I talked at length about what he did to the car, and why, and it also led to the fact that the motor was built to R4 specs by Michael Myer in Ohio. I've talked to Michael on the phone about the motor, and even though he built it about 10 years ago, he still remembers it.

    Anyway, the point of the post is this: it may very well have been the car-builder who put the carbs on it, and the man who's doing some work on it for me right now mentioned that he thought the carbs were much too big for such a relatively small motor; they're twin 600 cfm Edelbrocks. How does that jibe with what carbs were originally intended for the motor? Yes, the car is sometimes hard to start (as if the starter is too weak to turn the motor over easily even though there's a new battery), and it's easily flooded, but having had nothing in the past to compare it to, I don't know if that's just a feature of that kind of motor. Anybody have any constructive info or comments to offer ? Thanks to all. Mike Auldridge in MD

    Click image for larger version

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    Mike Auldridge
    Gaithersburg, MD
    301-651-4346
    SDC Life Member since 1976
    1948 M16
    1961 Lark VIII convertible (with minor mods)

  • #2
    I would say that 625-650 CFM would be plenty for that engine. I used to run
    a 700 double pumper Holly on my 383 MOPARS and that worked great.
    It seem people want to pour more gas into an engine that it can handle.

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    • #3
      I don't know if this will help but the Super Studebaker book says the carbs had 1-9/16" primaries and 1-11/16" secondaries Carter AFBs.
      Klif
      55 Speedster/Street Machine
      63 Avanti R2
      64 Convertible R1

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      • #4
        So does this engine actually have R3/R4 heads?

        Two 600 CFM AFBs are more carburetor than needed. There were some AFBs on some late 50's or early 60 Buicks that were smaller perhaps around 500 CFM. The dual carbs look nice but are not the best option for performance.
        David L

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        • #5
          I just looked at some info I had that indicated there were some AFB carbs as small as 400 CFM.
          Last edited by 64Avanti; 01-10-2016, 07:18 PM.
          David L

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          • #6
            I found this info on approximate CFM ratings for AFBs

            CFM ...Venturi .. Diameter ..... Bore Diameter
            ........primary...secondary....primary..secondary
            ------------------------------------------------------
            400 ... 1-1/8 ... 1-1/4 ......... 1-7/16 ... 1-7/16
            500 ... 1-3/16 .. 1-1/4 ........ 1-7/16 ... 1-11/16
            575 ... 1-3/16 .. 1-9/16 ...... 1-7/16 ... 1-11/16
            625 ... 1-1/4 ... 1-9/16 ...... 1-9/16 ... 1-11/16
            750 ... 1-7/16 .. 1-9/16 ...... 1-11/16 .. 1-11/16
            Last edited by 64Avanti; 01-10-2016, 07:28 PM.
            David L

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            • #7
              Way more carb than needed. Looks cool but not the way to go for max power or best performance at just about any rpm other than wide open.

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              • #8
                Click image for larger version

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ID:	1703295As you already surmised, the stock 625 cfm carb is already too large for any 289 (or 304) and two of them @ 1250 cfm is ludicrous. I rework the venturis (and air bleeds, and jets and metering rods) so each carb flows 370 cfm total. Much better throttle response, and 740 total is better. The good part of the two 4bbls is you can set up the progressive linkage so it will still be driveable.
                Bez Auto Alchemy
                573-318-8948
                http://bezautoalchemy.com


                "Don't believe every internet quote" Abe Lincoln

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                • #9
                  Progressive Ludicress

                  I love dual quads...work great on my grocery getter.....
                  Attached Files
                  sigpic

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                  • #10
                    That Lark convert is BEAUTIFUL!!!......Awesome looking engine too!

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                    • #11
                      Speaking of R4s . It's getting there.Click image for larger version

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                      Bez Auto Alchemy
                      573-318-8948
                      http://bezautoalchemy.com


                      "Don't believe every internet quote" Abe Lincoln

                      Comment


                      • #12
                        Originally posted by bezhawk View Post
                        Speaking of R4s . It's getting there.[ATTACH=CONFIG]50588[/ATTACH]
                        Looks VERY NICE!!....but remember Bez,...It's an R4 'Tribute'!

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                        • #13
                          How would you feed a engine now, with a 12 to 1 compression ratio? I would think that the R4 may not have been the best street engine.
                          Klif
                          55 Speedster/Street Machine
                          63 Avanti R2
                          64 Convertible R1

                          Comment


                          • #14
                            Originally posted by SN-60 View Post
                            Looks VERY NICE!!....but remember Bez,...It's an R4 'Tribute'!
                            This is a Tribute.



                            This is an R4 Avanti

                            , ,

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                            • #15
                              I thought R4s were just topped off with air cleaners,I know they're not common and not really sure now ?

                              Originally posted by sweetolbob View Post
                              This is a Tribute.



                              This is an R4 Avanti

                              Joseph R. Zeiger

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