Sluggish Acceleration (1970 Electra)

Discussion in 'Street/strip 400/430/455' started by Victor J Washington Jr, Oct 21, 2019.

  1. I have a 1970 Buick Electra with the original 455 - stock...needing some recommendations. Here’s the deal...from a dead stop, I can floor it and it’s sluggish off the line. Sounds as though its bogged down. Weird thing is, it'll peel off, but after that, it fights to get up to speed. Not the power I know these cars are capable of. I’m no expert on engine specs, but I believe the 70 Electras were rated at 360-370hp stock. Here’s what I know/have tried:

    1. Advanced the timing
    2. Plugs and Wires
    3. Replaced the coil in distributer (HEI)
    4. Rebuilt Carburetor
    Note: I've only run non-ethanol gas through the tank since purchasing in August
    5. Recurved the distributor

    The things mentioned above helped a little...but there is still much to be desired. I plan to do a compression test next to see if I getting weak compression from one of the cylinders. Also, there is an exhaust manifold leak. I've also considered the torque converter. Is there any way to confirm or eliminate if its the TC?

    known issues/history: Other than the sluggish take of, there are no other issues that I've noticed listening to it run at idle or in park. No knocking or tapping. However, there is an exhaust manifold leak on the driver's side.

    The engine was rebuilt sometime in the late 70s. In the owner's manual, there are notes explaining that when the engine was rebuilt, a 70-76 camshaft was installed in lieu of a 70-71 camshaft. I’m thinking that could very well be the issue. See the lift specs below.

    Exh. Lift .458
    Exh. Duration 332°
    Cam Spacing 117°
    Timing Advance * 124°

    Exh. Lift: .405
    Exh. Duration: 306°
    Cam Spacing: 113°
    Timing Advance: 113°

    If I have to go any further and dive into the budget says...put the stock cam back in, get new manifolds/gaskets, dual exhaust and stage 1 heads from TA Performace. However, a couple of local shops say it'll be cheaper to put an LS in it and call it a day. I'm not trying to make it a drag car and that's way over ny budget. Just trying to get decent HP. Between 360-400.

    Sorry for the dissertation. Any suggestions/recommendations?
  2. LARRY70GS

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

    Could be fuel pump as well. Can you tee in a pressure gauge? I doubt it is the cam unless it was installed wrong.
  3. My3Buicks

    My3Buicks Buick Guru

    I assume when you rebuilt the carb you replaced the accelerator pump?
  4. CJay

    CJay Supercar owner Staff Member

    When you floor the gas pedal, is the linkage and carb adjusted so the carb opens up fully?

    There's also an adjustment on the secondaries for the air valves so the engine doesn't bog. Too loose on the spring tension and it will bog out the carb
  5. A pressure gauge to check the fuel pressure? Never done it. What do I need?
  6. Yes, the accelerator pump was replaced.
  7. I haven't checked the linkage on the carb. When you mention the secondaries for the air valves...are you referring to the air/fuel mixture screws on the front of the carb?
  8. Philip66

    Philip66 Well-Known Member

    On a Quadrajet your primaries are the two small openings at the front of your carb, the secondaries are the larger two openings at the rear. The carb lets you run around at part throttle somewhat economically until you floor it.

    A Holley type carb has all four openings the same size. They are both four barrel...
  9. LARRY70GS

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

    Maybe more involved than you would like. You have to tee into the fuel line and run a small gauge that you can tape to the windshield and then drive the car. The easiest way with a Q-jet is to use some 3/8" fuel line hose and a tee. Unscrew the fuel line at the carburetor and buy a piece of steel line with inverted flare. Screw that into the carburetor and run the fuel line with a tee to another piece of hose and gauge.
  10. LARRY70GS

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

    The torque converter rarely fails without immobilizing the car completely. What can happen, and this is rare is a stator failure. The stator is what makes a torque converter more than a simple fluid coupling. It redirects fluid to multiply torque. There is a one way clutch that can fail affecting stator operation. This type of failure results in one of two symptoms.

    1, the car accelerates poorly to about 30-40 MPH, but then pulls well at higher speeds, or 2, the car accelerates well from a stop but top speed is limited to 40-65 MPH, the engine runs hot, and gas mileage is terrible. Again, this is rare.
  11. Philip66

    Philip66 Well-Known Member

    Victor I found this write-up online describing how to adjust the secondary air valve. It's pretty thorough and detailed, but I'm sure there are other ideas and opinions on the best way to make the adjustments. Read it several times to make sure you're familiar with everything and more importantly....take your time.

    The Rochester Quadrajet is one of the most common four barrel carbs out there; it was used in millions of GM and other vehicles, from the late 1960s through the late 1980s.

    It is a great carburetor, but it has a reputation for problems - including a stumble or bog under hard acceleration. This is usually caused by an out of adjustment secondary air valve - and is easy to fix.

    The Q-Jet's signature feature is its huge secondaries, which are controlled by engine vacuum - and spring tension. If the tension on the spring that controls the rate at which the secondary flaps open is not right, the result will be premature opening of the secondary air flaps, which causes the full-throttle stumble that plagues many out-of-adjustment Q-Jets.

    To make the adjustment, you'll need to remove and reinstall the air horn (the top of the carb casting). This looks a little intimidating but it's not difficult, if you are patient and careful.

    First, locate the accelerator pump rod & arm on the driver's side of the carb. The arm (usually, it's a greenish piece of metal is held in place by a press-in fitting that must be eased outpartially (not all the way!) in order to let the arm pop loose and hang free. Use a small punch or equivalent to slowly/gently drive the press-in fitting out just enough to let the arm pop out/swing free. Do not push it out all the way - or remove it - or you will have a chore on your hands getting it (and the arm) reinstalled.

    Next, (gently) remove the little screw that holds the secondary metering rods in place (the hangar that holds the rods is that thingy between the air valve secondary flaps). Put them aside, being careful not to drop them (they are fragile).

    Now remove the screws/bolts that hold the air horn to the carb. There are typically six screws (plus the two large front bolts that secure the carb itself to the intake) that need to be removed.

    You will also need to remove the small set screw on the passenger side of the carb that holds the choke rod in place on the primary side of the carb. Put the little metal tab that connects the choke rod to the carb someplace safe where you won't lose it! Let the rod hang free.

    Ok, now you are ready to - gently! - lift the air horn off the carb body. Try not to damage the gasket underneath as you do this. (If you do, replacement gaskets are easy to find - just be sure you get the exactly right one for your specific Q-jet).

    Now you can turn the air horn over and look at the underside. On the passenger side, to the left of the big air valve doors, you will see a small rod and a spring with a hook that "catches" the rod. This is the set-up that controls the tension on the air valve doors. The adjustment screw is on the side of the casing; there's a small allen bolt underneath that locks the adjustment screw/spring tension in place.

    To make the actual adjustment:

    * Gently loosen (but do not remove!) allen bolt to allow the adjuster screw to be turned out/adjusted.

    * Gently turn out adjustment screw to relieve all tension on the air valves.

    * Before adjustment, make absolutely sure (visually verify) the little spring/hook is just contacting the rod, with no preload or tension whatsoever. Be sure the air valves are closed/seated fully as you do this.

    * Now, carefully turn the adjustment screw in one full turn, then lock in place by tightening the allen bolt. (It may be helpful to carefully scribe or otherwise mark the adjustment screw in relation to the air horn body to absolutely be sure of "one full turn.").

    This will get you close to where you need to be. Button up the carb and then road test the car and see whether the bog goes away. Each application is different, so it may be necessary to repeat the process and make an additional adjustments; do these in quarter-turn increments and note the results until you get it dialed in.

    PS: The hardest part about reinstalling the air horn is getting it in place while keeping the primary side metering rods seated in their bores. They are spring-loaded and will "pop up" when you remove the air horn. Before you can reinstall the air horn, you'll need to - very carefully - re-seat the primary metering rods in their bores and then, using a small flatblade screwdriver (or thin knife) hold them in place as you lower the air horn onto the carb body. Do this with great care, being absolutely sure the primary rods are seated. They are very fragile and once bent, they're ruined.
    Also: Don't freak about the choke rod on the passenger side of the carb. It is a little awkward to get back on, but it's not that hard provided you are patient.

  12. The first symptom described is what I'm experiencing. Haven't had any issues with the top speed or running hot. Is there a way to diagnose or eliminate this as an issue other than replacing it?
  13. LARRY70GS

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

    If you don't have any issues with top speed, that usually eliminates fuel supply and pressure as a problem.

    Not that I know of.
  14. Would it be easier to take the carburetor off to do this?
  15. PGSS

    PGSS Silver Level contributor

    No vacuum leaks?
  16. It is, but I'm willing to put in the work to try and diagnose the issue. Thanks!
  17. None that I've noticed.
  18. LARRY70GS

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

    You don't need to remove the air horn to adjust the air valve spring tension. It is an awkward thing to do, but it is do-able with the carburetor in place.

    Yes, if the air valves flop in, it will create a bog, but before I would touch the spring tension, I would check the front choke vacuum break located at the front passenger side of the carburetor. The vacuum break serves two purposes, one, it opens the choke blade against thermostatic spring tension so the engine will run without loading up during cold fast idle. Second, it connects to a link that holds the air valves closed during low demand. With the engine running, check if the vacuum break is operating, vacuum should pull the vacuum break link in holding the air valves closed. With the engine running at idle, you should not be able to easily push the air valves open.

    Last edited: Oct 22, 2019
  19. telriv

    telriv Founders Club Member

    To All with Q-Jets,

    The vacuum break Larry is talking about is the primary choke pull-off. WHEN you put your foot to the floor of course you loose vacuum, BUT this pull-off doesn't usually react really fast. IF you look in the end it has a little metal piece in there with a small orifice in there to keep the pull-off from retracting too fast. This is ALSO a secondary air flap control as you can see it's attached to the flap by a rod. Back in the day we would drill the hole a little larger to facilitate a faster release rate which usually caused a bog.
    Now we had to adjust the tension spring usually tighter. There is NO NEED to remove the top of the carb/airhorn. Just get the proper size Allen wrench & loosen the adjuster & while holding the screw with a small screwdriver tighten it a quarter turn at a time until the hesitation/bog are gone.
    Once you have done this a few times you will be able to adjust it on the side of the road. IF you continue to tighten with no better results it's very possible the tension spring has broken.

    Tom T.
  20. Mark Demko

    Mark Demko Well-Known Member

    Personally I wouldn't even entertain a torque convertor issue, its very rare as Larry said.
    Examine the secondary air flap adjustment.

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