Reblt Carb back, still running a little rough

Discussion in 'Small Block Tech' started by 72skylarkconvt, Sep 12, 2020.

  1. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Well it still runs a little rough. arrg. I checked the wires last night to make sure they were connected to the correct places, they were correct.
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You are missing something. Bad wire, bad plug, or vacuum leak. Just a few possibilities. You need a mechanic that knows what he is doing, and doesn't mind working on older engines.
     
  3. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Well I have tried all I can. Unless the carb is still messed up after the rebuilt I don't know what else to to do.
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Did you ever take a vacuum reading?
     
  5. 72skylarkconvt

    72skylarkconvt Well-Known Member

    New wires, 2nd set this summer (new ones again when I bought the distib from TA), new plugs, I do have a bad grommet (rotted) PVC seats into the back of the intake, not a 100% seal, just noticed this last thurs when I was going over vac lines. Waiting for a new one to come in. I have the vac adv tee'd with the vac line that goes to device in breather that then goes to the door in breather snorkel (it works now, yay). I have the ported connection on carb blocked off.
    Could that vac ball or what ever it is called mounted on back firewall be bad? I did replace the line from it that plugs into the back of the carb.
     
  6. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Have not taken a vac reading. Don't have the device to do it and don't know how.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Get a vacuum gauge. They are not expensive. Get a reading with the engine fully warmed up idling in Park. It should be 18-20" and steady. If you suspect a leak, you can pinch off a line to the component and watch the gauge for an increase in vacuum.
     
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    See my post above. Probably one of the easiest things you can do.
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    BTW, the PCV valve does not need to be super tight in the grommet. That is NOT a leak source.
     
  10. 72skylarkconvt

    72skylarkconvt Well-Known Member

    On the compression readings. Are those in a range that indicates the motor is in good shape mechanically?
     
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yes.
     
  12. 72skylarkconvt

    72skylarkconvt Well-Known Member

    So I need a vacuum source for this test, where I am tapping into it on the motor? Carb port? Manifold connection somewhere, front, two back of carb?
     
  13. 72skylarkconvt

    72skylarkconvt Well-Known Member

  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Same source as your vacuum advance, air cleaner door, or climate control vacuum canister.
     
  15. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You mentioned that your air cleaner door is working. Do you have the tube in place between the air cleaner and exhaust manifold. The heated air tube.
     
  16. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Yes
     
  17. 72skylarkconvt

    72skylarkconvt Well-Known Member

  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  19. 72skylarkconvt

    72skylarkconvt Well-Known Member

    Doesn't some type of transmission control come up and get vac off back of intake? Could that control be bad (trans does shift fine even when you get on it) causing issues? When I got my carb they had the pc that screws into the back of it off. I just tightened it down till it stopped, did not force in any further. No sealant is needed on those threads?
     
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Vacuum modulator line, power brake line, climate control vacuum canister. Anything that is connected to engine vacuum can be leaking. That's why I told you to hook up a vacuum gauge and start eliminating things if it is low.
     

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