Join Shelby Forums Today

GT500 stalls at stop lights/signs

Discussion in '1965-1970 Shelby Mustang GT350 & GT500' started by Oregon Shelby, May 28, 2008.

  1. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    I am have a heck of a time trying to figure out why my car constantly stalls every time I roll up to a stop sign on my 1968 Shelby GT500. I have to leave her in neutral to keep the engine going, rev the engine and than slam her in gear to get her going.

    I have changed both radiator hoses, replaced the heater hoses and heater core. The heater hoses and core looked real clean and didn't see any clogs. I replaced them anyway. Used a spring on the bottom of the hose and there are no kinks. I have noticed where the bottom of the radiator and radiator hose is luke warm at best while the top is very hot to the touch. Is that normal?? Doesn't seem right. I don't believe my gauge is working as it states 3/4 hot. I replaced a thermostat last weekend with a 180 thermostat and drilled a hole to see if there were air pockets in the water. I also checked the thermostat in boiling water and it opened as normal. The cabs have been gone through and adjusted professionally. Should also note that the fan blade is on correctly and the fan shroud works like it should. I replaced the water pump with a brand new reman from Ford and also installed a brand new 4 core radiator.

    I checked for a head gasket leak by using the blue formula and the test came out negative.

    So several questions that I have that need some assistance. What would cause my car to stall when I roll to a complete stop and is it normal for the bottom hose to be luke warm while the top is very hot to the touch. Does the flow come from the bottom of the radiator to the top? If so, why is the top so darn hot and the bottom so darn cool? If you need further clarification, please let me know as I am at a loss of trying to read trouble shooting books.

    look forward to some suggestions,
    brian-
     
  2. 66gtk

    66gtk Well-Known Member

    Posts:
    86
    Likes Received:
    0
    Joined:
    Apr 30, 2006
    My car (HiPo 289) does the same thing, and I have replaced all the same items, except I haven't replaced the carb yet. Mine only behaves like this when it is fully warmed up. I sometimes have to put the clutch in and tap the gas as I approach a stop.
     
  3. zrayr

    zrayr Well-Known Member

    Posts:
    446
    Likes Received:
    11
    Joined:
    Oct 30, 2005
    Location:
    TX
    normal. coolant travels from the engine to the top radiator hose, through the radiator & the bottom hose, then back to the engine.

    Z. Ray



     
  4. Mike Christie

    Mike Christie Well-Known Member

    Posts:
    54
    Likes Received:
    0
    Joined:
    Jan 18, 2006
    Location:
    Colorado, USA
    My 66 350 died at a stop occasionally and I traced it down to the carb. area. It was the little diaphram (sp?), It might be called a dash pot ( I'm probably wrong on the name as it was 30 years ago or so) but when the throttle lever returns to an idle position, it contacts a spring/diaphram valve (dashpot?) and allows a less abrupt return to idle. I know I didn't explain this very well, the the part bolts to the left front carb mounting stud between the carb and the hex nut. My Shelby was an automatic but I think the same part was also on standard trans models as well. Hope this helps,
    Mike
     
  5. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Thanks for the suggestions.
    Pony carbs completely went through my carbs. I than had a local well known carb shop adjust my carbs specifically to my car. My car is an automatic if that makes a difference.

    ZRay,
    I agree with you. I thought the water flowed from the engine to the top of the radiator hose, down through the radiator and existing from the bottom of the radiator back to the engine. I can see where there might be a change in temperature for the first 20 minutes of the engine being warm because its getting cooled by the radiator. I would assume that both hoses would ultimately be close to the same as far as temperature and they are not. I didn't use a thermostat and could see the flow of the water run from left to right. Now with the thermostat is in place and the car being warm, I don't see a flow from left to right, but do see heavy steam coming out and no movement of water when I open the radiator cap. Again, I did check to see that the thermostat was working before I installed it and it is placed in its correct position within the thermostat housing.

    I am going to try and check for air pockets in the engine. I am going to undo my top heater hose and let the water shoot out. Hopefully I notice signs of eratic pressure coming out which would indicate a pocket of air in the engine.

    I would appreciate any other suggestions. I am thinking of installing my original radiator instead of this brand new larger 4 core radiator.

    thanks,
    brian
     
  6. steveshelbymustang

    steveshelbymustang Well-Known Member

    Posts:
    336
    Likes Received:
    2
    Joined:
    May 20, 2006
    When you started explaining the symptoms of stalling my first thought was the dash pot like Mike Christie referred to. If you are running a different cam the engine vacuum may be low and not allowing the power valve in the carb to function properly. When the vacuum is low the motor you would have a hard time adjusting idle. Its like the timing is advanced and takes a while to return to normal after you rev it up. Very annoying!!!
     
  7. zrayr

    zrayr Well-Known Member

    Posts:
    446
    Likes Received:
    11
    Joined:
    Oct 30, 2005
    Location:
    TX
    Looking at your first post, I don't see that your cart is overheating? If it is not overheating, then don't worry about the hose heat differential.

    Secondly, with an automatic you need a dash pot on the carb, do you have one? If you don't have a shop manual, get one ( available on CD ) & set the dash pot yourself.

    Also if your floats are not in proper adjustment that can cause the dying when coming to a stop. Have you checked that?

    good luck, and keep us posted.


    Z. Ray
     
  8. Mike Christie

    Mike Christie Well-Known Member

    Posts:
    54
    Likes Received:
    0
    Joined:
    Jan 18, 2006
    Location:
    Colorado, USA
    Oregon Shelby, you mentioned that you had your "carbs" adjusted. Do you have more than one four barrel carb? Is this a big block or small block engine?
    Mike
     
  9. corbins

    corbins Active Member

    Age:
    68
    Posts:
    28
    Likes Received:
    0
    Joined:
    Sep 7, 2005
    Location:
    Va
    Hi- if this is a automatic car, based on my miserable experience over a 2 summer period, you have a bad converter in the tranny. If its a 4-spd - keep chasing all the things already mentioned. Only took those 2 years to figure mine out and probably $1000.00 of money wasted away on all the wrong things.
    Good luck
     
    Last edited by a moderator: Sep 21, 2010
  10. 68Shelby2014

    68Shelby2014 Well-Known Member

    Posts:
    51
    Likes Received:
    0
    Joined:
    Apr 6, 2006
    Location:
    Portland, Oregon
    Just to clear up some issues.
    The engine is a 428 with H/M intake with two 4 barrel carbs.
    :thumbup:
     
  11. Mike Christie

    Mike Christie Well-Known Member

    Posts:
    54
    Likes Received:
    0
    Joined:
    Jan 18, 2006
    Location:
    Colorado, USA
    OK, assuming you have two Holley 600 or 650's. If memory serves, I think the front carb primaries are responsible for idle. If so that is where the dashpot should be located. Make sure it's there and working. This is the simplest place to start, as well as making sure all the basic tune up, plugs, points wires timming etc; are all good.
    Question, do you notice any black smoke when it's stumbling and trying to idle, like an extremely rich mixture, coming out of the tail pipe? If so, I would check the carb floats like zrayr mentioned.
    Also, check to make sure you have good manifold vacuum.
    Best of luck,
    Mike
     
  12. crzy4shelbys

    crzy4shelbys Well-Known Member

    Posts:
    202
    Likes Received:
    1
    Joined:
    Aug 20, 2007
    Location:
    Trabuco Canyon, CA, USA
    Based on the original post, I interpret the problem to be that it won't idle when it's in gear, not that it won't idle at all. Unless I'm reading the description wrong, he puts it in neutral to keep it running, then when he's ready to go, he rev's it and slams it into drive to avoid stalling.

    If it's idling in neutral, that eliminates quite a few of the suggestions for what to check (although they're all very good and informed suggestions).

    Perhaps I'm wrong in my interpretation... can you provide input, Brian?

    Josh
     
  13. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Josh,
    My car will idle just fine when the car is in neutral. If I notice traffic in front of me, I will simply place the car in neutral and wait for the traffic to roll. The car won't stall at this point. If I place her in gear while the traffic is slowly going forward, I am ok only as long as the car is moving forward and I can see the traffic in front moving at a regular pace. If I am in traffic and am following a car that is constantly slowing down and speeding up with the flow of traffic, I have to toggle between keeping the car in neutral and placing the car in first or the car will die.

    I should also point out that I have to keep moving on a hill at all times. If I slow down at all going up a hill the car will die. I can't go up a hill slowly!

    As 68shelby notes, I have a Holman and Moody dual quad set up on my 428engine that was placed on the car from the late 60's to early 70's. I decided to leave that set up on there. I took the engine out several summers ago to simply paint it and both carbs were gone through and refreshed by Pony Carbs. I than installed the engine and I am now finding problems that I hadn't noticed before.

    I don't have any black smoke coming out of the car even though I have black soot that sprays out along with moisture at the start of the engine.

    I must admit that I am a novice at engines although I am learning real fast. I read about about the dash pot. I have never had a dash pot on my carb before, but am willing to try it this weekend.

    Have I answered the questions below? If not, feel free to ask again

    Again, do appreciate the help

    brian
     
  14. rsimkins

    rsimkins Well-Known Member

    Posts:
    449
    Likes Received:
    7
    Joined:
    Jan 13, 2006
    Location:
    Eastcoast USA
    Brian,

    From your description I assume that your car is an automatic, but have not seen a definitive statement to that effect (but of course I may have missed something). Is it an automatic?
     
  15. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Yes, its C6 automatic car
     
  16. shelbnut

    shelbnut Active Member

    Age:
    62
    Posts:
    42
    Likes Received:
    0
    Joined:
    Aug 27, 2005
    It really sounds like you have a vacuum problem somewhere.
    Check all vacuum lines for any leaks.
    Are you running the spacer between carb and intake to keep heat from causing vapor lock?
    Might also check the gaskets and mounting of carb to make sure it's not sucking air between intake and carb.
    Is your vacuum advance on the distributor working properly?

    Russ
     
  17. crzy4shelbys

    crzy4shelbys Well-Known Member

    Posts:
    202
    Likes Received:
    1
    Joined:
    Aug 20, 2007
    Location:
    Trabuco Canyon, CA, USA
    My experience with vacuum leaks is that they cause a fluctuation in idle and it would be independent of whether or not the car is in gear. Regardless, the easy way to check for a vacuum leak is to spray carb cleaner around the base of the carbs and around any vacuum lines connecting to the manifold (keep in mind carb cleaner can be harsh on painted surfaces) being careful not to let it get sucked in the air cleaner. If the idle speed goes up, vacuum leak. If it were my car, I wouldn't check that though because it really doesn't sound like a vacuum leak to me.

    My guess is corbins had it right, and the problem is in the transmission. If the torque converter isn't functioning properly, you'd have the problems you've described. If it were my car, I'd take the shade tree mechanic approach to diagnosing the problem, and try to flutter the throttle JUST enough to get it to go in gear without dying, then I'd see if I can run the RPM's up just a little, to say between 1000 and 1250, while applying the brake. If it feels like your really having to lay on the brakes to keep the car from trying to go, then I'd take a closer look at that torque converter.

    Josh
     
  18. KensKR

    KensKR Well-Known Member

    Age:
    60
    Posts:
    85
    Likes Received:
    2
    Joined:
    Nov 16, 2005
    Location:
    Virginia
    Brian, if your toque converter is dying. Check your transmission fluid for a burn't smell, and metal particles.
    Kenny
     
  19. OVERRIDE

    OVERRIDE Well-Known Member

    Age:
    64
    Posts:
    223
    Likes Received:
    4
    Joined:
    Dec 21, 2004
    Location:
    elgin il
    It also be the fuel is boiling in float bowls. Does your card have a dash pot on it if so checkec adjustment. check float level with car running pull side plug if the fuel is running out that is to high. You want it to when you rock your car a little bit the fuel should just start to run out. Or try your fuel enrichement
    screws, if you have a vacuum gauge hook it up below throttle plates turn screws in till engine starts to run rough then back out slow to you get you highest vacuum reading. Then do the same with the other screw.
     
  20. patty.dilabio

    patty.dilabio Well-Known Member

    Posts:
    327
    Likes Received:
    5
    Joined:
    Nov 26, 2006
    Hi to all! Just a thought on stalling after reading all these posts.Have you ever tried to stop useing the handbrake?If there is a vacuum leak in the booster,it may only occur when you apply the brake pedal.It is easy to try,and it will let you know if it is a booster problem.One other often overlooked vacuum line is on the transmission modulator valve,make sure you check it.Go over the simple stuff first.....it is important to work in steps,and not jump around.Good luck and please:) keep us posted
     

Share This Page