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Replacing CD 150 in '69 Alpine

Discussion in 'Huskies, Imps, Rapiers, Fastbacks, etc.' started by Bill Blue, Oct 3, 2021.

  1. JBS

    JBS Donation Time

    Not wanting to hijack Bill’s post but for information only Alpine Innovations in the UK now have a new intake manifold and Weber 32/36 Carb conversion kit for the Rootes Arrow range of cars such as the Fastback Alpine / Rapier , Hunter & Sceptre with the cantered over engine. Only suitable for use with the Alloy cylinder head. So not suitable for Bill’s car with the cast iron head. Jerome.
     
  2. RootesRooter

    RootesRooter Platinum Level Sponsor

    For those with iron-headed Rootes-mobiles, has anyone ever mounted modern carbs on the twin carb manifold from '57-'58 Rapiers or Gazelles?
     
  3. husky drvr

    husky drvr Platinum Level Sponsor

    RR,

    I don't recall anyone discussing that change. I think i recall a poster from "down under" who tried to sell a set of those carbs and manifolds. Being unsuccessful, he installed them on his late Minx and liked them.

    I do recall some discussion about changing out Zeniths for Weber ICT's or ICH's on an Alpine manifold. I don't believe that project has ever been completed, though.

    Don
     
  4. Bill Blue

    Bill Blue Platinum Level Sponsor

    Man, but that was a long time ago. As I recall, an owner even purchased the carbs but never seemed to finish the job. Still sounds like a good idea.
    Bill
     
  5. husky drvr

    husky drvr Platinum Level Sponsor

    Bill,

    I agree, it does sound like a good idea.

    IIRC, the person who originally purchased the carbs, for whatever reason, decided that he wasn't interested in the conversion and sold them on. The purchaser, I think, was in the midst of a restoration and didn't have a running engine.

    Maybe one day we'll hear about the installation and performance of the conversion.

    Don
     
  6. Bill Blue

    Bill Blue Platinum Level Sponsor

    The carb arrived today. Very good looking. Machining is very good, no casting flash or sharp edges. The spare jets look to be top quality. Just hope the thing works as good as it looks. Mounting it is going to be a trip. It mounts using tapped, blind holes in the body. The old carb bolts into blind holes in the manifold. Somethings got to give. But first, I've got to learn how this thing works.

    Bill
     
  7. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, maybe a piece of exhaust tubing about 2" long, 1/4" flange with proper bolt pattern both ends? You will have to hook a choke cable up to the enrichment knob too. I bet it will run great once you figure out the right jets.
     
  8. husky drvr

    husky drvr Platinum Level Sponsor


    Bill,

    Is your carb similar to the ones in this video?

     
  9. Bill Blue

    Bill Blue Platinum Level Sponsor

    Yes, the same and I'm very lucky, S&S has done a very good job of documenting the installation and tuning of the carb. My biggest mystery is the dizzy hookup. The vacuum nipple on the carb is on the engine side of the throttle plate. However, it not only is exposed to engine vacuum. it seems to be attached to airfow on the filler side, plus a third outlet I have yet been able to identify. I really do not care about these details, I just want to know it the dang thing will operate correctly on a conventional dizzy.
    Since motorcycles engines are very similar in operation to the 1725, I have to guess the answer is "Yes". But I'd like to know and not guess.
    Bill
     
  10. 260Alpine

    260Alpine Silver Level Sponsor

    Bill. The other outlet is for a overflow hose.
     
  11. Bill Blue

    Bill Blue Platinum Level Sponsor

    Yes, but that is not the outlet I was referring to. I mean there are three paths for the air that goes to the distributor to enter the outlet. I have identified two of them. I suppose I should not call them outlets, but rather an air inlets. By that I mean entering the path to the distributor. Or perhaps it would be more accurate to say modifying the pressure of the air to the distributor.

    Bill
     
  12. Barry

    Barry Platinum Level Sponsor

    Bill,

    My Sportster days ended in the mid-'70's and my Big Twin days never were, but I don't recall any H-D V-twin engines using a canister style vacuum advance distributor. Starting in the mid-'80's, H-D used a Vacuum Operated Electrical Switch to achieve an "on / off" version of vacuum advance, but I have no idea how the vacuum line was plumbed. Some info here:

    Never say never, but I doubt that the S&S carb has a traditional "idle transition" vacuum advance port. Maybe a "manifold vacuum" port for a VOES setup or for positive crankcase ventilation???
     
    Last edited: Oct 12, 2021
  13. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, you could use the port for PCV and drill and use a smaller tube for vacuum advance.
     
  14. Bill Blue

    Bill Blue Platinum Level Sponsor

    I think that I read that S&S developed the carb for use on their engines. They later adapted it for the Big Harleys. So far, everything I have read is tilted toward use on Harleys. They simply say the port hooks up to the VOES port and everything will be fine. So no help there. Any idea what the S&S engines used? One thing I'm pretty sure of is that the port is not a source of manifold vacuum. I say that because there are two other source of air in that circuit. Also, the fitting orifice is small, somewhere in the 50-60 thou range, which I think eliminates it from the PCV conversation.

    Bill
     
  15. Bill Blue

    Bill Blue Platinum Level Sponsor

    But I don't know where the source of ported vacuum would be.
     
  16. 260Alpine

    260Alpine Silver Level Sponsor

    Bill, Are we talking about the port with the rubber cap in this pic? vacuum port.jpg
     
  17. 260Alpine

    260Alpine Silver Level Sponsor

    You can use manifold vacuum for the distributor as long as you limit the can to 10 degrees. Manifold vacuum is below the butterfly, ported above the butterfly.
     
    Last edited: Oct 12, 2021
  18. Bill Blue

    Bill Blue Platinum Level Sponsor

    Yes.
    Bill
     
  19. Barry

    Barry Platinum Level Sponsor

    That port appears to be completely "behind" the throttle blade and would therefore be full manifold vacuum for any throttle blade position.
     
  20. husky drvr

    husky drvr Platinum Level Sponsor

    Bill,

    I wouldn't worry about using full manifold vacuum, except you might have to make an advance stop for the vacuum can. A limit of about six degrees at the distributor (12 crank degrees) is what I've seen discussed as a limit for this method considering how the additional advance affects the engine idle. Now be advised that those discussions usually involved an engine with more compression and a stronger cam than what you've got in the Alpine. You've got about 8.4:1 compression and a very mild cam. You can probably go a bit higher on limits due the slower combustion process of lower compression.

    If you can acquire an Alpine distributor (sIV better than sV) to try instead of the O/E one, I think you would notice a big difference. I also think you might have some detonation in the mid range RPMs.

    Just a few thoughts and hope this helps.
     

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