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Rochestor 2G Fuel problems

Discussion in 'The Hokey Ass Message Board' started by hudson48, Feb 6, 2013.

  1. carbking
    Joined: Dec 20, 2008
    Posts: 2,914


    I am going to mildly disagree on the need for a regulator.

    I just checked the factory shop manual for the Rochester 2G series used on mid-1960's Pontiac. MINIMUM ACCEPTABLE PRESSURE OF 5 1/4 psi. Less than that and Pontiac considered the pump defective.

    When I still had my '64 GTO with factory tripower (Rochesters), I ran better than 6 psi and had no issues.

    And I regularly run 7.5~8 psi on the 2 Carter AFB's on my shop truck.

    The issue that MAY cause the need for a regulator is the failure to properly rebuild the carburetor. Each carburetor was designed by engineers with certain design limits. Rochester produced fuel valves for the 2G series from about 0.082 to 0.118. There were also a number of different floats for the 2G series WITH DIFFERENT BUOYANCY!

    Acquiring a "one size fits nothing" rebuilding kit with a much larger than normal fuel valve orifice will upset the balance of the float system, and then a regulator may be required to prevent flooding. But if this balance is disabled, then the fuel level in the carburetor may vary with RPM. Remember that with a mechanical fuel pump, the pump speed increases as the engine RPM increases. Obviously, not true with an electric pump.

    Basically, the regulator is a "band-aid". Use the proper parts inside the carburetor, and the regulator, at least for street use, is unnecessary. Please also remember, this thread is about Rochester 2G's, not Holley AA-1's or Stromberg EE-1's.

  2. hudson48
    Joined: Oct 16, 2007
    Posts: 2,665


    My Holley pump is rated at 7.5 psi.I have purchased a regulator and gauge and will fit this up this weekend.I think I mentioned earlier that the front carb will stick open slightly and not return to fully closed and this is creating a vacuum problem and fuel squirting in as soon and as long as it is opened.
    The regulator is a 0-4 psi so the max I can go is 4 psi obviously.Hope this smooths things out for me.
  3. Put return springs on EACH Carb!!!
  4. hudson48
    Joined: Oct 16, 2007
    Posts: 2,665


    With the linkage that Larry supplies there is a return spring on the front and rear carbs built in to the linkage ends.I am looking at that as being perhaps some of the problem and will investigate further.
    Larry(Automation) says that the springs he supplies for the secondary carbs are all that is needed.Of course I have a full return spring setup on the primary carb but on the left hand side.
  5. dickster27
    Joined: Feb 28, 2004
    Posts: 3,169

    from Texas

    They are called torque springs. It is the way GM made sure the secondary carb plates were closed. BUT...if your secondary plates have any leakage all the springs in the world won't help.
  6. fatstax
    Joined: Sep 15, 2010
    Posts: 52

    from cobourg

    i rebuilt a rochester i had a few years ago and the gasket that seals the top of the carb to the bottom got messed and the vaccum was sucking extra fuel into the engine from the leak, make sure you are sealed properley
  7. Larry Fulton
    Joined: Jul 3, 2011
    Posts: 31

    Larry Fulton

    Paul purchased one of our "Master Builder" kits, which we sell many of without complaint.

    Realize, that while we do provide all of the necessary parts, instructions, procedures and our proven recommendations to build your own set of properly functioning hot rod tri-power, we do not have any control over the actual usable condition of the end users carb cores.... or the assembly of the end product.

    Paul, if you need further help and or advise about our product, procedures or recommendations, please contact us directly by phone... I'm here for you as I'm with all of our customers.


    *they are called Torsion Springs... and IMO - this thread, like others contains much misleading &/or improper information... but than again, if it works for you, it must be right.
    Last edited: Feb 14, 2013
  8. hudson48
    Joined: Oct 16, 2007
    Posts: 2,665


    I would like to emphasise that I have no problem with the product that Larry supplied(see post above) and he has been very helpful with my questions that I have had during the process.

    I found the rebuilding quite easy and I did start with carbs that were rebuilt and running OK but didn't have the correct bases(all 3 had idle circuits) they all had power pistons and two had the old style floats.

    The quality of the bases and the linkages is excellent and it would appear that it is just some teething problems to get it right.

    I did find out that my fuel pump is a 7.5 psi and I am fitting a regulator and gauge to go to the 5-6 psi that Larry recommends in his instructions.
    That should be done today and a test drive later to see how that works.
  9. Dirty2
    Joined: Jun 13, 2004
    Posts: 8,903


    Well said !

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