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3 2GC's a weepin'

Discussion in 'The Hokey Ass Message Board' started by Marshall Metal Shaping, Jul 1, 2011.

  1. Hey Guys

    I've been shakin' down my 'A' with only the primary carb of the tri-power fed.
    The other day I plumbed the secondaries. Here's my quandry..these guys are weeping fuel. I lowered the fuel level,but am still experiencing load-up. The secondaries are the real deal..not just another set of 2GC's. Would a minute leak past the throttle plates cause vacuum to "pull" fuel through the venturies? I do not believe I have any vacuum leaks as I get good metering through the idle /air adjustments on the primary carb and as soon as you monkey with the secondary throttle plates(vacuum leak) the engine dies.

    Any help greatly appreciated!!

    [​IMG]
     
    Last edited by a moderator: Jun 1, 2014
  2. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    at idle speeds, you can't slightly open a seconary carb/s without stalling, because there are no idle circuits.


    Fuel weeping where?

    on a real outboard carb with no idle circuit, I would think a whole lot of air flow would be needed to pull fuel.

    also, to see how much throttle plate vac leaks at idle on outboard carbs; get a clean rag to be able to close off the carb top to see if you get a speed change.

    Also, you can make a block off carb base gasket to eliminate one carb while you get the other outboard to work, then work on the last one.
     
  3. I had a problem on my secondaries due to the return springs on the 2GC's not being stiff enough.
    The slightest drag on the progressive linkage would crack them open just slightly, but enough to drip in some fuel.

    I added a small spring to the linkage instead of trying to fix the Rochester springs in the base.

    3X2 Cadillac intake on a Stude.
     
  4. As I said the secondaries are original and have no idle circuits, I also think it would take a lot air to "pull" fuel. I am just curious of all aspects.
    Thanks


     

  5. Piewagn
    Joined: Mar 25, 2009
    Posts: 1,163

    Piewagn
    Member

    Do you have a pressure regulator inline? The secondary carbs only like 4.5 psi at most.......or you will be overwhelming the floats!
     
  6. also did you replace the floats
    te black lacquered floats get saturated and get heavy and sink causing high float level

    and as marshal said if the springs are weal it will open them slightly

    also make sure the linkage is not draging
    and the tie rod between the outters is adjuster to
     
  7. Toner283
    Joined: Feb 13, 2008
    Posts: 1,327

    Toner283
    Member

    ^^^ What he said. The secondary carbs should have an extra spring on the throttle shaft to keep them closed until the driver opens them with his foot.

    The throttle blades on the secondary carbs should also be about 3/16ths thick and if they were removed from the shafts or if they were added to the extended shafts when the carbs were changed over they might have issues sealing against the throttle bores in the base plate. An air leak here will cause all kinds of screwy tuning issues.

    And like Piewagn said, double check the fuel pressure too.
     
  8. seatex
    Joined: Oct 24, 2006
    Posts: 2,660

    seatex
    Member

    I have had the same issue with my 2gc's, as well. A big assed flat spot when you transition to the the secondaries. Carb rebuild helped a lot, but still have a bit of a stall when I nail it.
    Kinda" like having a steering wheel for a belt buckle, IT'S DRIVIN' ME NUTS!
     
  9. Make sure the seat of the needle and seat is tight. I bought a factory Tri -power and ran it for a few years, it slowly started loading up at stop lights and heading up hills. It took a few times pulling the carbs aprt to realize what was going on. Also there is a product called Dag 213 that even the factory used on their carbs to seal the front and rear carbs. You can get it from Tripower Mike. Mike Wasson http://www.pontiactripower.com/index.html
    I had to drill the idle air bleeds on the center carb when I bolted the Trips to a high compression 400 Pontiac and it was amazing what performance I gained!
     
  10. KoolKat-57
    Joined: Feb 22, 2010
    Posts: 3,027

    KoolKat-57
    Member
    from Dublin, OH

    Fuel pressure about 3lbs., check out pontiactripower.com for the secondary throttle shaft return springs.
    This guy knows tripower on this web site!
     
  11. Piewagn
    Joined: Mar 25, 2009
    Posts: 1,163

    Piewagn
    Member

    Make sure the accel pumps work good in the secondaries, with a manual progressive linkage, it will ALWAYS drop the nose during transition.......
     
  12. gonzo
    Joined: Dec 24, 2003
    Posts: 1,792

    gonzo
    Member

    What size jets are you running? (I use 52 in my stock Olds 324)
    Are your accelerator pumps ok? Mine go south every year or so.
    Are all internal vents clear? Crap ethanol laden fuel goes south in a matter of weeks and can wreak all sorts of havoc on carbs, especially clogging small vents.
    Good luck and POST WHEN YOU FIND THE SOLUTION! I hate it when people don't follow up with their tech solutions.
     
  13. Hi Guys

    Where do I start??...The fuel pressure crossed the desolation that is my mind...makes sense. The carbs are plumbed in series from a stock mechanical pump. The secondary return springs are no issue...it takes a gorrilla to pull the two carbs open!! As I said earlier they are correct issue as they do have the thicker throttle plates. I am confident the accelerator pumps are fine as I get no bogg or transitional flat spot. I have no binding issues with the linkage, as I have designed a progressive assembly isolating the primary and secondary carbs. Any ideas or pics regarding a clean compact pressure regulator? This begs the question...why does the primary carb have no issue with pressure, unless the idle circuit "bleeds" off enough excess pressure while the engine is running....same reason the secondaries only load up at idle, as part throttle or cruising reduces pressure to them....?

    Thanks to all...this kinda shit keeps you thinking!
     
  14. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    If you can't tell if air is going through the 2 outboard carbs at idle, make solid base gaskets.

    If both carbs are weeping, you can just try the solid gasket on one to save work.

    If that carb is now not weeping, you had air flow though the venturi. Another indication would be that the engine idle speed went way different with one carb blocked off.

    I'd disable the linkage to the outboards so that the throttle blades won't tear the gasket.


    But, if that blocked carb still weeps, it could be a needle problem, float problem, or fuel pressure issue.
     
  15. I have kagel regulator. fuel pressure is 2.5 to 3 pounds on a 383 small block. Driven a lot
    65000 miles no leaks runs like a scalded dog. I know guys running a 348 pump for 3'2s and have no trouble. The stock pump has about 6 lbs which is too much.
     
  16. Where do I find a "kagel" ...got any pics?
    Thanks
     
  17. cooger
    Joined: Nov 5, 2008
    Posts: 233

    cooger
    Member

    I've got the big base (Pontiac) end carbs with a stock center. The only way I've ever been able to set up a tri power is to block off with plates the ends, the center should make the car run just fine, good idle, good vac. etc. If that happens (you have to make it happen) then go to one end carb at a time and bring it on line. Should be no change at all---if so, then you have a vacuum leak through the throttle bores on the ends-can prove it by taping the top of the carb in question.
    I used the vintage speed bases on mine-aluminum body, brass Tplates that give a super tight seal. Cost some bucks, but well worth the it since it eliminated all the hassel.
    BTW, I use a stock pump, stock center carb stettings, and float levels as recommended by the Rochester books. Good idle, decent milage, vac. around 17".
    Running 11/2 year now.
    Good luck.
    cooger
     
  18. No regulating fuel pressure?
    Thanks


     
  19. Angliaman
    Joined: Jun 19, 2007
    Posts: 67

    Angliaman
    Member
    from Forney, Tx

    Had the same problem with mine. Changed to a low pressure pump and solved all my carb problems....
     

    Attached Files:

  20. cooger
    Joined: Nov 5, 2008
    Posts: 233

    cooger
    Member

    nope, no need to regulate fuel pressure. Think of the stock Pontiac/Olds setups as used when they brought them out--they didn't regulate fuel pressure, if a pump failed you went to the auto parts store and bought a new one, put it on and went.
    cooger
     
  21. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    I had a set up just like yours. I opened up the idle circuits on the end carbs and used about 1/8 open on the mixture screws with the plates as far closed as they would go. This solved all the idle problems.
     
  22. There should be no idle circuits on the Tri powers he is talking about. I believe all factory Tri powers had no idle circuits.
    The only way you should get nozzle drip is the needle and seat aren't sealing. Its either the needle and seat failing to seal , the seat is loose as I said before, the float is too high or too high of pressure Period. There are no other reasons for fuel drippage.
     
  23. Also make sure that the secondaries( front and rear) only open at about 3/4 throttle on the center carb. The front and rear shoud be set up to be closed at about 3/4 to all the way open at full throttle. They have to be set up this way or they won't work at all.
     
    Last edited: Jul 5, 2011
  24. I just re -read the first post and the second poster is correct. At idle you cannot open the front and rear as the vacuume leak will kill the engine.
    Where are we standing on this issue?
     
  25. Tim morrison
    Joined: Aug 23, 2009
    Posts: 68

    Tim morrison
    Member

    I had the same problem with mine. I put return spring on both of the secondary carbs and adjusted the fuel pressure to 3lbs, I had it at 4 1/2lbs and it was to much 3lbs works great.
     
  26. Piewagn
    Joined: Mar 25, 2009
    Posts: 1,163

    Piewagn
    Member

    I've dealt with this problem..........fuel pressure overwhelming the secondary floats!! You need a regulator! Primary carb won't weap, because the engine is using the fuel. When you are running on just the primary, you force open the needle with too much pressure in the secondaries......the high pressure fuel has no where to go.......


    [​IMG]
     
    Last edited: Jul 6, 2011
  27. Piewagn
    Joined: Mar 25, 2009
    Posts: 1,163

    Piewagn
    Member


    Although, the primary carb will have idle and power valve circuits. Only the secondaries are devoid of this circuitry.......
     
  28. cooger
    Joined: Nov 5, 2008
    Posts: 233

    cooger
    Member

    correct. Only the primary has all the "guts". The end carbs have bigger throttle blades cut at a different angle for sealing-no acc. pump, idle circuits, etc. They are just a "dump" at full throttle.
    Like A.HOLES, every one has one-an opinion that is. Running a stock Chevy fuel pump on mine has never had a problem, no regulator.
    cooger
     
  29. There is something else wrong if you need to run a regulator to run Trips. Think about it, how many factory units were out there without any type of regulators. Lets see, Corvette, Pontiac, Oldsmobile, and a mdrid of others. And guess what, no regulators? Hmmmm. Also there are over a million 2 bbls out there without regulators. The tripowers that we have here are all based on the 2Gc 2 bbl so as far as the pressure overtaking the seat , its just plain not going to happen unless you have a pump that is putting out alot more pressure than a stock pump. All the lines are at equal pressure. The ends cannot have more pressure than the center. They are joined by a T.
    The Baseplates from vintage speed still leak a small amount of vacuume. I have a set on mine and run stock sets on others. The only way you can get the vacuume to be the most minimal is to use Dag 213 as the factory also did. You cannot cover the actuall top of the carb with tape as even with the minimal vacuume leak that they have will start sucking fuel from the wells as the vacuume is enough to draw the fuel.
    Lets start over.
    You open up the front and rear at idle and it dies. This will happen as the front and rear have to open only at or near 3/4 open throttle or the engine will die. This is fact.
    Why are you saying you are seeping? Do you actually see fuel dripping when its idling?
     
  30. Piewagn
    Joined: Mar 25, 2009
    Posts: 1,163

    Piewagn
    Member

    My "stock" pump was pushing 11 psi. As per the instruction sheet that came with my setup from Charlie Price at Vintage Speed, "install a pressure regulator with fuel pressure set at no more than 4.5 psi." I read the sheet after I had my problems, installed a regulator and it corrected them........

    A single 2GC is constantly consuming fuel when the engine is running. That's what was on mine before I installed the Tri Power. My only issues were with the secondaries after the installation until I installed a regulator. This is not my "opinion", it's my actual "experience"...
     
    Last edited: Jul 7, 2011

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