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Technical 2 BBL Carb suggestions for a flathead, Rochester 2G, Carter BBD, Stromberg WW , others??

Discussion in 'The Hokey Ass Message Board' started by kilohertz, Oct 22, 2021.

  1. kilohertz
    Joined: Oct 5, 2020
    Posts: 74

    kilohertz
    Member
    from Vernon, BC

    I have a 239 C1BA flathead in my '49 F-47 with an AOD and I want to put the Merc manifold on it, which I already have, and it has the small base 2 BBL 3 1/4"x 1 7/8" stud spacing with I think 1 3/8" bores. I am having a hard time finding the small base Rochester 2G locally but I found a Stromberg WW in my collection and today a Carter BBD from an 80's Jeep, all the correct stud spacing and bore size. The Carter is complete with electric choke, looks pretty good.

    I would like to hear of your experience with these various carbs, good/bad what to look out for etc. Maybe there are others out there I am not aware of.

    Look forward to a great discussion.

    Cheers

    PS forgot to mention that I have machined a GM points distributor for this and it uses regular ported (or manifold) vacuum source so no need for the special vacuum source for the original distributor.
     
    Last edited: Oct 23, 2021
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  2. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    "Kilohertz", I never thought of those alternative carbs; keep us informed of what you find!
     
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  3. I have a 2g Rochester on my flathead in my F-1 pickup. Runs great, been on there for 10+ years. Also running a converted GM distributor(points).
     
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  4. 41rodderz
    Joined: Sep 27, 2010
    Posts: 6,540

    41rodderz
    Member
    from Oregon

    The small base carbs are out there , you just have to run into the right guy that has made his mind up wether he is going to use them . ;)
     

  5. kilohertz
    Joined: Oct 5, 2020
    Posts: 74

    kilohertz
    Member
    from Vernon, BC

    Thanks guys, I'll find out tomorrow if the 7 Rochester 2Gs I found are small or large base...

    In the meantime, here is the Carter BBD I found today from a 89 Jeep YJ.

    cheers IMG_0533.JPEG IMG_0534.JPEG IMG_0536.JPEG
     
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  6. Flat Roy
    Joined: Nov 23, 2007
    Posts: 533

    Flat Roy
    Member

    That carter is a big one. Rochester 2G ranges from about 225 cfm in the smallest applications up to what Rochester calls a 435 cfm. I ran a 381 CFM 2Jet (no modifications) on my 264 8BA and it performed very well (now super charged) however the motor is really suped up. also did a little port work on the manifold to flow better. Milder engine would probably run better with a smaller one.
     
    Last edited: Oct 23, 2021
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  7. Flat Roy
    Joined: Nov 23, 2007
    Posts: 533

    Flat Roy
    Member

    Here's a picture Rochester 2Jet.jpg
    made a pretty fancy adaptor to make it work.
     
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  8. 1946caddy
    Joined: Dec 18, 2013
    Posts: 2,060

    1946caddy
    Member
    from washington

    Last edited: Oct 23, 2021
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  9. v8flat44
    Joined: Nov 13, 2017
    Posts: 1,211

    v8flat44

    Kilohertz, you might try to p m Charlie NY, he is on here. He has done more than a few carbs for these engines & runs them on his test engine.
     
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  10. carbking
    Joined: Dec 20, 2008
    Posts: 3,715

    carbking
    Member

    Small base Rochester 2GC - every Ebay vendor and swap meet vendor "KNOWS" that ALL small base Rochester 2GC carbs (especially the one they have) is a center carburetor for any factory tripower :rolleyes: and therefore priced accordingly!

    The Carter BBD was Carter's cheap (price leader) 2-barrel. Not overly reliable, and virtually impossible to re-calibrate. I would use this unit ONLY on a numbers-matching show-car! (The same is true for the BBD's sister 1-barrel, the BBS).

    The Stromberg WW is an excellent carburetor, once bushings have been added to the aluminum throttle body.

    Carter's better 2-barrel carbs were the WCD and WGD models. Extremely reliable, and both use AFB jets, and springs, but NOT rods.

    The Carter WCD, WGD, or Stromberg WW, if one is chosen with a similar displacement to your engine, would make a good unit for you.

    Jon
     
  11. kilohertz
    Joined: Oct 5, 2020
    Posts: 74

    kilohertz
    Member
    from Vernon, BC

    Okay thank you! Great info and thank you for the pictures.

    I'll leave the BBD at the wreckers. I'm heading out to my shop shortly and I'll have another look at the WW to see it's condition and if it's complete. I am waiting to hear from someone close by who has 7, 2G's to determine if they are small or large base.

    Thanks again for the replies.

    PS, could someone please explain to me the 3 dimensions quoted on carb data sheets? We have flange, throttle bore and venturi. I know what the venturi is but what is the difference between the flange and the bore? What is the dimension called for the butterfly opening? I see mention of SAE flange of 1 1/4", is that an actual dimension or a "name" for a certain size flange? So if the small base 2G has a flange of 1 1/4", is that the actual diameter of the butterfly valves? thx!
     
    Last edited: Oct 23, 2021
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  12. joel
    Joined: Oct 10, 2009
    Posts: 2,467

    joel
    ALLIANCE MEMBER

    My choice was a 2G.
     
  13. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    One big advantage the 2G series have is that, when mounted backwards, the fuel line and throttle linkage just about fall into place. The choke is all wrong though, but if you go with an automatic choke (which Mercury's have), it drops right into place as well. You just have to match a divorced choke carb to a divorced choke manifold and an integral choke carb to an integral choke manifold. I have done both and the divorced choke requires only a slight bending of the actuating rod, while the integral choke only needs a shortening of the heat tube. I know, I know, real men have manual chokes, but these work so well when set up correctly that they are a pleasure to have.

    I was a little apprehensive at first about running the carburetor backwards, but they don't seem to mind a bit. The only problem I ran into is that the stock Ford throttle linkage won't open the 2G all of the way. I extended the throttle linkage so it would, but then I lost the correct "feel" on the throttle so I put it back to stock. One of these days, I am going to correct the problem, probably with a cable on a scroll, but my car runs and performs so well that the project just keeps getting shelved.

    I don't have any information about the mounting problems (or lack thereof) of those other carburetors because the 2G works so well that I don't think it would pay to spend time finding out.

    BTW, I found these guys who are selling clean 2G small base cores for $49 and $79, depending on type : http://hotrodcarbs.com/store/small-base-rochester-2g-2gc-2gv-carburetor-cores.html.
     
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  14. kilohertz
    Joined: Oct 5, 2020
    Posts: 74

    kilohertz
    Member
    from Vernon, BC

    Thanks Denny, et. al.

    As I am starting from scratch on the entire throttle setup, (not using the original as it didn't come with my truck) I have two pedal options, one comes out on drivers side, the other on passenger side, so I can use the Rochester installed "correctly" without issue. I also may use the in-tank pump with a regulator to drop to about 4 PSI, I went with a 90's GM van tank with the lower pressure pump, I think 20-30PSI. My other option is to just suck fuel through the in-tank pump with the stock (new) pump I have to run the carb. I am planning on a custom throttle rod, I have some really nice 1/4" stainless tubing here which will look awesome, just need to order the ends, Mmmm wait, I have a dual carb Heim joint setup from a VW engine which could be used. Cool. :cool:

    For the choke, I would ultimately like an electric choke and I know they are available for the Rochester, possibly others, but if not my Merc manifold had divorced choke, all that remains are the holes so I would have to find the Merc choke guts.

    Anyway, heading to the shop to check all my options...the out of town 7 2G carb guy said he'll have measurements for me in an hour.

    Cheers
     
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  15. This will help seeing from a distance, 1" wrench size filter nut, front feed (3/8") inverted flare fuel line is most likely a large base. Side feed 1" filter nut, 5/16" I.F fuel line is most likely small base. Front feed with 1/4" pipe thread NO filter nut is most likely small base. These are Chevrolet styles, Pontiac and Oldsmobile differ.

    It helps a little when scanning a swap meet or online.
    Stromberg WW carbs are good, but make sure the threads are ok for the fuel line fitting.

    Also I was under the impression you need to open up the bores in the Merc manifold for the Rochester carb. I've run them on a 8BA with an Offy adapter backwards........Super easy to fit on, like they were meant to be there.
     
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  16. Good catch, I forgot about that. I used a die grinder to open up mine... a machine shop could probably do a more precise job though.
     
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  17. kilohertz
    Joined: Oct 5, 2020
    Posts: 74

    kilohertz
    Member
    from Vernon, BC

    Well shoot! 10 out of 10 carbs....all large base 2G.

    My WW is toast, base cracked and butterfly shaft is missing the actuator flange.

    The search continues.

    Cheers
     
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  18. Flat Roy
    Joined: Nov 23, 2007
    Posts: 533

    Flat Roy
    Member

    I also used a Merc intake (see above) . could not open the manifold enough for the big base with grinding. Would have to reconstruct the cast iron top. That tall aluminum riser has taperd thoughts.
     
  19. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    Again, I used a device called a Rota-Broach in my drill press to bore my manifolds, initially using a spare 2G base as a guide. Bolt the base to the manifold, mount the manifold on the drill press and just bore down. I have done both cast iron and aluminum Mercury manifolds this way and it was quick and easy. The only complicated part is getting the manifold mounted in the correct position on the drill press. Once you get it so the broach moves easily in the guide, you have it right.

    The proper Rota-Broach is 1 7/16". You will need to purchase an arbor as well. They are kind of expensive, but probably a bit cheaper than a trip to the machine shop. I needed the extra 2G base for a subsequent carburetor rebuild so I made an alignment guide out of 1 1/2" thick aluminum, using the carb base. You can bore all the way down. I then use a die grinder to smooth the transition.

    If I were in Minnesota, I could send the setup to anyone who needed it, but alas, I am in Florida for the winter.


    RotaBroach.jpg
     
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  20. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    That was pretty much what I thought would happen when I realized that all of the carbs I could make out in the picture had front mounted fuel inlets. It looks like a good initial rule of thumb would be to look for carburetors with side-mounted fuel inlets (Chevrolet).
     
  21. carbking
    Joined: Dec 20, 2008
    Posts: 3,715

    carbking
    Member

    Many of the early (50's) 2GC with small base had front mount fuel inlets.

    Jon.
     
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  22. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    True, but they are still kind of scarce. I maintain that if one were to find a random cache of 10 front inlet 2G's, the overwhelming probability is that they would all be large base.

    Early fifties anythings are getting to be quite rare. Remember, they would be at least 65 years old.
     
  23. The early front feed Chevy 2G had just a pipe threaded hole not the filter housing nut.....at least that's how I tell the difference from a quick look at the swapmeet.
     
    Last edited: Nov 17, 2021
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  24. 41rodderz
    Joined: Sep 27, 2010
    Posts: 6,540

    41rodderz
    Member
    from Oregon

    I have the Stromberg WW and a few small base Rochesters . I hate to see you struggling to find a good carb but I hate to unload mine. Put a wanted ad on here .
     
  25. Bird man
    Joined: Dec 28, 2009
    Posts: 895

    Bird man
    Member
    from Milwaukee

    Exhibit A
    1955 Pontanic:
     

    Attached Files:

  26. I edited my answer to Chevrolet......Pontiac and Olds had a filter nut in front but I'm not sure if they're small base and they look different so you can't confuse them with the Chevy version.
     
  27. kilohertz
    Joined: Oct 5, 2020
    Posts: 74

    kilohertz
    Member
    from Vernon, BC

    Thank you for the offer, but....

    I just found acquired another few 2Gs, these ones all small base. I'm just working my way thru them now, some have frozen shafts, some missing rods, I should be able make one good one from them. Not sure if the air horns are interchangeable, some have integral chokes, some divorced, ultimately I will be fitting an electric choke to the integral housing...

    Does anyone know if the air horns are interchangeable, different vacuum/air passages?
    Same for the bases, can they be swapped between different small carbs?

    cheers
     
  28. carbking
    Joined: Dec 20, 2008
    Posts: 3,715

    carbking
    Member

    If the numbers on the identification tag are IDENTICAL, and some yahoo has not switched the tags, then the airhorns are interchangeable. If the tags have different numbers, PROBABLY NOT. If the tags are missing, PROBABLY NOT.

    Just because the "casting blank" numbers on the castings are identical does NOT make the castings interchangeable.

    The "casting blank" (the raised number on many castings) is an internal number for the bare casting BEFORE the casting is machined.

    Can some of the non-interchangeable items be made to function? Probably, IF you are a carburetor engineer.

    Take a look at the second line in my signature block.

    Good luck.

    Jon.
     
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  29. Lem Chesher
    Joined: Aug 18, 2021
    Posts: 16

    Lem Chesher
    Member

    I was going to build a 3 duces for my 327 30 years ago I went to ever junkyard I could find looking for 2g side mount fuel line carbs I found 7 of them . I traded them all to a fellow named Charlie down in Florida for one complete restored one. He did a beautiful job. I hope to run it on my 1950 Mercury flat
     
  30. tubman
    Joined: May 16, 2007
    Posts: 6,917

    tubman
    ALLIANCE MEMBER

    True thirty years ago, unfortunately, not now. The jury's out until it is running on your car successfully.
     

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