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Technical 2GC question (and a tip)

Discussion in 'The Hokey Ass Message Board' started by bchctybob, Jan 2, 2018.

  1. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
    ALLIANCE MEMBER

    I while back I acquired a '28 Ford roadster with a fresh 283 and three twos backed by a TH350.
    It seemed to run OK but not quite "right". It almost always needed to be choked to start, pumping the gas pedal didn't seem to do much. Lots of cars have starting quirks so I ignored it as long as it ran fine. Well, the other day it didn't run fine. The plugs were wet with fuel. Turns out the acceleration pump in the center carb wasn't working and the front carb was leaking into the manifold.
    The Problem; The front carb just had the proverbial booger in the needle and seat - done. But when I opened the center carb everything looked perfect. So I blew out everything and started to reassemble it. The pump would move but still no squirt. The override spring was taking up the motion and the seal wouldn't move. So I swapped the spring with another - same thing.
    The TIP: The bore showed slight corrosion so I polished it with some Mother's Metal polish. The plunger now descends like it should and it squirts fine. I thought I'd pass along the tip that even a little corrosion can stop the pump from working like it should with the blue plunger seal they supply now days.
    Now for the question: When I pulled the booster venturi assembly out to clean everything I noticed that the emulsion sleeves that drop into the carb body and surround the emulsion tubes were missing. It seemed to run OK without them but I scrounged up a set and installed them. What do they do and can they be left out? Are they present in all 2GCs or just certain models?
    The engine is back running well again, the idle is consistent but I have a little off-idle hesitation that I need to work on. Anyone have any thoughts or wisdom?
    IMG_0718.JPG
     
  2. They are anti-percolation tubes. Most 2g and 4g's had them. If you have blocked the exhaust heat in the manifold, then no, you'd probably never miss them. Race unit wouldn't need them , for instance.
    On the other hand, with the heat , you could have a problem on a hot day, in traffic, etc.
    Stumbling, erratic idle, etc.
     
  3. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
    ALLIANCE MEMBER

    Sounds like where you and I live they are best left in, gets over 100 here every summer. I was curious because these carbs looked like they were professionally rebuilt/set up and the tubes were left out. I wondered if it was a little known speed secret. Thanks.
     
  4. 302GMC
    Joined: Dec 15, 2005
    Posts: 5,083

    302GMC
    Member
    from Idaho

    I use a ball de-glazer on the pump barrels. I consider it part of a thorough cleaning.
     
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  5. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
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    That sounds good, but doesn't it leave a "sanded or honed" finish? The blue seal that was in mine seemed to stop or try to roll backward with just the slightest blemish in the bore. That's why I polished it.
    For my AFBs I've been saving the leather seals and soaking them in Neatsfoot oil to revive them. I haven't run across any leather seals in the 2GCs.
     
    Elcohaulic likes this.
  6. 302GMC
    Joined: Dec 15, 2005
    Posts: 5,083

    302GMC
    Member
    from Idaho

    Lubed w/ PB Blast or even water, the finish is a fine crosshatch polish.
     
    LOU WELLS likes this.
  7. carbking
    Joined: Dec 20, 2008
    Posts: 2,237

    carbking
    Member

    Leather accelerator pumps DO come in the better, more expensive rebuilding kits for the 2-GC Rochesters.

    Jon.
     
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  8. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
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    Thanks Jon. What brands do you consider good kits? and where do I order them? I'll try to use them in the future. Out here we only have two local parts stores, O'reilly and NAPA and you know what they sell.
     
  9. carbking
    Joined: Dec 20, 2008
    Posts: 2,237

    carbking
    Member

    There are currently several brands of carburetor rebuilding kits available at the FLAPS; but I believe all come from two manufacturers: Walker and Weatherill Associates and are reboxed as necessary. These will not have leather pumps.

    There are also a number of different manufacturers of custom rebuilding kits for older vehicles, which sell either on-line or via telephone.

    The advantages of the FLAPS kits are price, local availability, and see-through packaging so you can actually determine what parts are in the kit.

    When ordering from one of the custom manufacturers, ASK your questions BEFORE placing the order! If the seller doesn't wish to help you, try a different manufacturer.

    Jon.
     
    Last edited: Jan 3, 2018
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  10. manyolcars
    Joined: Mar 30, 2001
    Posts: 7,390

    manyolcars

    I have been installing rebuild kits in my carburetors for many years. I follow the instructions carefully but every one runs rich. Black sooty tailpipes. Should I set the floats lower?
     
  11. carbking
    Joined: Dec 20, 2008
    Posts: 2,237

    carbking
    Member

    The white or light gray tailpipe that was the mark of a well-tuned car 40 years ago was...............residue from the lead!

    Today, a well tuned engine will exhibit a very dark brown or black tailpipe. One that spends much of its life in city driving can be sooty.

    Having said that, NEVER believe the instructions that come in the FLAPS kits!!!! These are generic instructions for a group of carburetors, and you know the saying "one size fits all, works well for none"!

    Factory service manuals are readily available for virtually all vehicles using O.E. carburetors and will have the specifications tested and approved by the engineers.

    If you have an aftermarket setup, then you become your own engineer. Wide-band testers are NOT that expensive, and MUCH less expensive than guessing.

    And one other thing to remember: an engine with a PERFECTLY TUNED CARBURETOR and DEFECTIVE IGNITION will run RICH!

    Jon.
     
    302GMC and partssaloon like this.
  12. FLAPS??? o_O

    I'm sure I've seen the definition before, but please refresh my memory. :confused:
     
  13. tubman
    Joined: May 16, 2007
    Posts: 3,674

    tubman
    ALLIANCE MEMBER

    Friendly Local Auto Parts Store.
     
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  14. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
    ALLIANCE MEMBER

    Jon; Mark answered part of my question about the tubes but I was wondering, in your experience, are there 2GCs that come without the tubes in the body? I ask because I wonder if I did the right thing by installing a set from another carb. Actually, I used the main body that came with the tubes because the acceleration pump area of my original body looked like it had been damaged and was out-of-round.
    Both bodies are #7008597.
     
  15. carbking
    Joined: Dec 20, 2008
    Posts: 2,237

    carbking
    Member

    Lots of the two barrel 2-GC carbs came without the tubes. They were also used on a few of the four barrel type 4-GC carbs.

    Cannot tell from casting number alone, need the tag number of the carburetor to determine if/if not tubes were originally used. The casting number on the body is the internal number for a "blank" casting BEFORE machining. The castings may be machined many ways for use on different carbs. Example:

    1957 Olds J-2 front carb (no idle screws, 1/8 inch pipe tap on rear)
    1957 Olds J-2 rear carb (no idle screws, 1/4 inch pipe tap on rear)
    1957 Pontiac tripower rear carb (no idle screws, no tap on rear)
    1957 Pontiac tripower center (idle screws, 1/8 inch pipe tap on rear)

    All of the above have the same casting number. These are quite obvious, but calibrated drilled passages are less obvious. Generally speaking, NOT a good idea to interchange castings unless from identical tagged (even to the engineering status code) carburetors.

    Jon.
     
  16. Bob, If there is a small recess in the casting for the flange of the anti-perc tubes to locate on , then the ones you installed won't hurt a thing...'Course I'm not a King...Maybe a Duke by now. LOL
     
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  17. manyolcars
    Joined: Mar 30, 2001
    Posts: 7,390

    manyolcars

    thank you carb king
     
  18. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
    ALLIANCE MEMBER

    There was a recess for the tubes in both castings. Thanks a lot for the info guys, I really like messing around with carburetors but detailed info like that is not easy to find. I've got books and manuals for some of them but still there is always some little nagging question not covered - like the tubes.
    I have about 30 2GCs in my stash not counting the ones I have on various manifolds up on my shelves. I try to buy only Tri-Power and/or Chevy linkage ones and preferably not the ones in the picture I posted, I like the side inlet versions. Since they are all swap meet carbs very few of them still have their tags. I don't swap parts unless there is a darn good reason, I've been pretty lucky with my swaps so far I guess.
    Thanks again, Bob
     
  19. does anyone know of a tech write up on the use of a wide band sensor for tuning these multiple carb installations??
    What is required, the procedures needed to get it right, the "right" A/F mixtures???
     
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  20. Can anyone weigh in on setting up the butterflies on the out board carbs of a tri-power? I've got three 2GC's and and the idle circuits have been removed from the outboard carbs and all that and it runs okay for the most part but I've noticed when it's idling in the driveway that if I physically grab the two outboard carbs and push the throttle linkage closed just a little beyond where it rests that it idles just a little better. I've read that some guys will file fit those throttle blades for a perfect fit. Any comments on that?
     
  21. manyolcars
    Joined: Mar 30, 2001
    Posts: 7,390

    manyolcars

    some use epoxy build up to seal the butterflies
     
  22. saltflats
    Joined: Aug 14, 2007
    Posts: 8,519

    saltflats
    Member
    from Missouri

    You do need the thick butterfly's in the end carburetors.
     
  23. Just one comment...

    DON'T! :eek: ...if you can avoid it.

    I'd consider filing to be a last resort approach. The design and fitting of the throttle plates is a lot more precise and complicated than it appears at first glance. I'd do anything I could to avoid even removing them from the throttle shaft.

    If they don't want to close completely at idle there may be some sort of idle stop adjustment that can be "altered". You might need a heavier throttle return spring. Or more likely there is excessive wear on the throttle shaft and/or throttle shaft bores in the throttle body.

    Sometimes the bores can be re-bushed. But even then it can be a tedious job to get the throttle plates back in the proper place in the throttle bores. They need to be nearly completely closed in the throttle bores yet open and close smoothly and not stick open or bind anywhere in their range of travel.

    It can be done of course, but don't rush the job. Be patient and meticulous and if at all possible do not remove or even loosen the throttle blades from the throttle shaft.
     
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  24. check with Dickster in TX. last I knew he had the original formula for the sealing goop GM used.
     
  25. Thanks for the tips fella's. Hope this helps others too.
     
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  26. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,298

    bchctybob
    ALLIANCE MEMBER

    That's one reason I collect them when I can, some have very loose fitting blades and some have perfect fit. Those are the ones I convert for use as end carbs.
    Claymart has good points, I avoid removing the blades too but sometimes you can loosen the screws slightly and improve the seating of the blades. Then re-stake them.
    I'm getting close to putting together my 324" Olds and I'd love to run the 6x2 Weiand Drag Star intake I have for it but I'm not sure I want to deal with 6 old carbs at once. How do you guys do it!?!
     
    ClayMart likes this.
  27. ^^THIS !^^

    An oversight on my part... :oops: There's a reason why those screws are such a pain in the ass to remove. :rolleyes:
     
  28. saltflats
    Joined: Aug 14, 2007
    Posts: 8,519

    saltflats
    Member
    from Missouri

    Keeps me out of the bars at night. ;)
     
  29. JOECOOL
    Joined: Jan 13, 2004
    Posts: 2,645

    JOECOOL
    Member

    At one time someone on here did a tech piece on how to install these an modify them for 3x2 setups . It was several years ago I read it but it was a good tech piece.
     

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