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Technical SBC stalls when put in gear, can't start hot:

Discussion in 'The Hokey Ass Message Board' started by c-10 simplex, Jul 24, 2021.

  1. Wrench97
    Joined: Jan 29, 2020
    Posts: 679

    Wrench97

    Good point what trans are you running?
     
  2. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    i'm leaning that way too......but where?!?

    i'm not getting any vacuum with one cover plugged and the pcv valve in the other cover. This was at about 1100-1200 rpm. i have to say that my dipstick tube situation may not be entirely sealed very well......so both tests (vacuum with both covers plugged and vacuum test with one cover plugged) may not be entirely accurate?

    i sprayed around the intake and heads with carb cleaner again as i did last week, but couldn't find anything.

    i don't think trans is the problem because:
    1) TH-350 non-lockup AND i can keep it running in gear with foot on the gas----or if the curb idle is jacked up to like 2000rpm

    2) i unplugged the vac modulator because i was using that particular vacuum outlet on the manifold for vacuum readings.
     
  3. Joe Travers
    Joined: Mar 21, 2021
    Posts: 708

    Joe Travers
    Member
    from Louisiana

    You mentioned PCV hose on carb fits poorly.

    Joe
     
  4. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    That turned out to be B.S.---- i don't know what i'm doing and actually have very low automotive aptitude.

    Now, i did block off (properly this time....) pcv and brake booster and the vacuum is now up to 17-19 depending on rpms.

    It's also a little bit easier to start hot, whereas before i couldn't get it started at all hot.

    So, the brake light was coming on recently, but i ignored that because i didn't consider that to be a major problem right now. So, the brake booster could be leaking.

    However, the stalling when put in gear is still there. So with this test, i don't think brake booster is the sole cause?

    Sprayed carb cleaner again around intake to head area as well as china wall area----nothing.

    Pushed down the accelerator pump just by itself, not the arm and throttle, just the pump and it slowed rpm way down for a sec then back to "normal" rpm. But i don't think carb is the problem.
     
    Last edited: Jul 28, 2021
  5. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    So, things going on indicate rich, but i turned the idle-mix screws inwards, but the rpm and vacuum readings actually went down.
     
  6. gary macdonald
    Joined: Jan 18, 2021
    Posts: 308

    gary macdonald
    Member

    Egr , q-jet base gasket leaking or wrong type .
     
  7. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 5,217

    2OLD2FAST
    Member
    from illinois

    So , the brake warning light comes on & you don't " think" that's a problem ?
     
  8. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    EGR opening was sealed off with a plate. The base gasket is the same one/type i've had for the past 4 yrs. i sprayed carb cleaner between the carb and intake and got nothing...:(
     
  9. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    Obviously it's a problem. i don't consider it an immediate problem in the sense that if i can't get the engine to keep running, i'm not driving the car on the street.

    i'm going to correct the brake issue, but my thinking was get the engine right, then fix brakes.
     
  10. gary macdonald
    Joined: Jan 18, 2021
    Posts: 308

    gary macdonald
    Member

    Do you have an adapter plate on the manifold for the Q-jet ? Just curious. What intake , factory or aluminum aftermarket.
    Advance the timing till it stalls , back off and see if it helps , the balancer outer ring could of slipped and rotated , giving the wrong timing mark location. Just a guess ? Good luck
    To advance, looking down on the distributor, the vacuum canister is moved counter clockwise.
     
  11. gary macdonald
    Joined: Jan 18, 2021
    Posts: 308

    gary macdonald
    Member

    Can you post a pic of the engine and intake manifold?
    I just watched the video , Im postive your base gasket on that manifold is incorrect. Seriously, q-jets have 2 different designs . Remove carb and flip it over with your base gasket on it . Youll see the problem , there’s a little gap on one side . Please , please check .
     
  12. 5brown1
    Joined: Apr 13, 2008
    Posts: 234

    5brown1
    Member

    I had a similar problem which turned out to be a broken sprag in a newly rebuilt torque conveter
     
  13. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    The video is not actually mine---i just referenced in off 'Tube.
    Stock factory iron q-jet , manifold. Same base gasket for the past 4 yrs.

    The more i'm reading, the more the could be a possibility apparently----even with a non-lockup converter.....!
     
  14. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    So, is stalling/not stalling basically boiling down to a function of if good vacuum and timing is right, it should not stall?
     
  15. gary macdonald
    Joined: Jan 18, 2021
    Posts: 308

    gary macdonald
    Member

    Got it , thankks for responding.
     
  16. kevinrevin
    Joined: Jul 1, 2018
    Posts: 189

    kevinrevin
    Member
    from East Texas

    You said you adjusted the carb, then gave it a "spirited" test drive and the issue started.
    Is there another known-to-be-good carb you can swap, just to see if yours is the issue?
     
  17. Joe H
    Joined: Feb 10, 2008
    Posts: 1,525

    Joe H
    Member

    Double check the secondary linkage, make absolutely sure that it is not holding the shaft open.
    Back the fast idle adjustment off so it's no where near touching the primary throttle shaft.
    Plug all ports on the carburetor. ( PCV, trans, brake, dash, distributor, etc...... )
    Pull the distributor cap and make sure the mechanical advance is not stuck or a weight is out of place.
    Pull the fuel inlet line off the fuel pump, add a length of hose that will reach an aux. fuel jug full of fresh fuel.
    Plug both valve cover holes.
    Pull dipstick and plug the tube hole.
    See how it runs at this time.

    If it doesn't run properly at this point,
    Replace carburetor with good know working unit with fresh base gasket. No adaptors, use the same type of carburetor.

    If it still doesn't run properly,
    Pull all 8 spark plugs
    Install solid piston stop in #1 cylinder
    Hand turn the engine till the piston hits the stop, MARK the balancer where the ZERO is on the timing tab.
    Hand turn the engine the opposite direction till you hit the piston stop, MARK the balancer where the ZERO is on the timing tab.
    Is the original timing mark on the balancer in the center of the two mark you just made?

    Does the exhaust have a burnt oil smell? It should if you have an internal vacuum leak.

    Run-on, hard start, high idle tells you the engine is getting air from somewhere it's not suppose to. Stalling out is also a sign of extra air coming in, as it's to lean to run. Until you can get the idle down, spraying for vacuum leaks is not likely going to work.
    For testing proposes, cut up an aluminum can and slip it under the secondary openings of the carburetor to make it into a two barrel. You can't drive like this due to interference of the throttle blades, but it's a good test to try.
     
    Last edited: Jul 31, 2021
    David Gersic likes this.
  18. Well it also requires sufficient compression, a burnable air/fuel mixture and an ignition system of sufficient output.

    Just to be sure if you aren't already aware of it . . . While you're making idle speed adjustments keep in mind that there are probably two separate idle speeds that can be set.

    One setting is called "curb idle" which should adjust idle speed when the engine is at operating temperature and the choke is fully open. The other setting is usually referred to as "fast idle" and comes into play during cold starting and engine warm-up. The "fast idle" screw should contact the fast idle cam only when the choke is applied during cold starting and engine warm up. When the choke is fully open the fast idle cam should move in such a way that the fast idle screw no longer contacts the steps on the cam.
     
  19. 51pontiac
    Joined: Jun 12, 2009
    Posts: 391

    51pontiac
    Member
    from Alberta

    So just spitballing here but to me the key is that it was running ok, you ran it a bit hard and it immediately started running crappy. This indicates to me that it likely is something like slipped timing or messed up ignition…weights or springs. Fuel delivery could be an issue as well.
    Here is what I would try.
    …pull all plugs to make sure they are not oil or gas fouled. Clean, check gap and reinstall.
    …pull distributor cap and rotor to check weights, look for any arcing or red dust in cap, rotor and under coil. Check condition of wires.
    …check timing again, first with vacuum advance plugged, then with it connected. Try both ported and manifold vacuum advance.
    …this next one is one a lot of people miss if they have a solid inline fuel filter near carb. Replace it temporarily with a cheap clear plastic inline filter. When car starts cold, is filter full of fuel? After it warms up to operating temp is it still full of fuel or is it full of fuel vapour and only a little fuel trickles in? If it is vapour lock it may still run but not well.
    I would try the above simply because they are easy to do, cheap to try and don’t take a long time. If everything checks out ok you have eliminated so possibilities from the list.
    Good luck.
     
  20. c-10 simplex
    Joined: Aug 24, 2009
    Posts: 1,371

    c-10 simplex
    Member

    Thanks for all the suggestions---i will definitely try them. i intend to do everything whole-hog and thoroughly. i have just been busy with work. i think we are close.
     
  21. mlinton1941
    Joined: Oct 17, 2012
    Posts: 626

    mlinton1941
    Member

    spray carb cleaner around the carb base and intake, sounds like a vacuum leak to me !!
     

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