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What am I missing?

Discussion in 'The Hokey Ass Message Board' started by maniac, Aug 15, 2009.

  1. maniac
    Joined: Jul 11, 2005
    Posts: 539


    My buddies 56 Nomad, 327, 10 to 1 comp, hydraulic roller cam, MSD dist and box.

    We changed the Torker manifold to a Performer, with a 670 Holley street avenger, now the thing will only run with the vacuum advance disconnected, and not that great, but it is driveable to point, as soon as you connect it, it backfires and stumbles and won't even move.

    No vacuum leaks that we can find, it actually has steady vacuum when it idles, which is pretty much all it will do, unless you disconnect the advance.

    Timing is on 8 BTDC and total is around 30. doesn't misss, just runs terrible, not fouling plugs either, checked and the dist is in right, firing order correct.

    I feel like I'm looking right at the problem, but just don't see it.

    What do you guys think ? We are stumped:confused:
  2. Alienbaby17
    Joined: Sep 13, 2005
    Posts: 918


    Is this the same ignition set-up you were running prior to switching the intake and carburetor? If it is I would rule out a problem with the ignition box or distributor itself. I would be curious about whether the distributor was maybe off a tooth...
    Is this a brand new carb or was it known to be good before?

  3. wrenchn
    Joined: Mar 29, 2009
    Posts: 33

    from Chicago

    It could be your crank pulley spun on the rubber, Take vac hose off dist. check vac with a guage at manifold and turn dist for max vac and then back off dist until vac drops down 2" on the gauge.Hook vac hose back to dist. Then try it if you are still having problems you can try ported vac to dist.
  4. maniac
    Joined: Jul 11, 2005
    Posts: 539


    All the same stuff, just changed the manifold, ran great before.

  5. brigrat
    Joined: Nov 9, 2007
    Posts: 5,337

    from Wa.St.

    You say vacuum is steady but what is it?
    Where are you hooking the advance up to, what port?
  6. maniac
    Joined: Jul 11, 2005
    Posts: 539


    Steady at 14 or so, on a manifold port
  7. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 25,529

    Jalopy Joker

    Do not have your answer. But, have a ZZ4 factory GM crate motor that comes with most everything including HEI distrib, except carb, etc. I had trouble from day one with it pinging on premium gas, correct timing, etc. Finally a guy suggested putting cap on distrib vacuum and carb outlet. Runs better than it has in years. Do not know why.
  8. dave lewis
    Joined: Dec 12, 2006
    Posts: 1,362

    dave lewis

    You are advancing the timing at idle if you have it hooked to MANIFOLD vacuum port.
    Most common small block chevy set up is to run PORTED vacuum = no vacuum at idle. That would be the fitting just above the idle mixture screw on the passenger side front of the carb.
    Try hooking it there, set your timing @ 10 deg. advance at idle.
    good luck
  9. You should have the distibutor advance connected to a ported vacuum. That is no vacuum at an idle and more vacuum as you raise the RPM. Not to manifold vacuum.
    Last edited: Aug 15, 2009
  10. Ya, what Dave said. You don't want Vacuum at idle in the can. Go above the butterflys.
    The Wizzard
  11. Lunatic
    Joined: Sep 28, 2004
    Posts: 1,199

    from Carson,Ca.

    yes... ported vacuum for vacuum advance

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