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
    Ok great suggestions.
    The car is running around 1100. I have been told that is a bit high. I checked the temp around different parts of the engine and it was around 200. Exhaust manifold around 300. Intake manifold around 185, thermostat around 180 radiator around 200, water around 180 etc. My gauge must not be working it point straight up to the norm for the first 20 minutes and than gets slammed to the right. Again I am constatnly checking the temp with a temp guage that seems to be working normal.

    I am at the point where I simply need to take the car in too have it checked. The problem is that the major Ford Big block techs here are out 6 months! Not sure I want to trust someone who really doesn't know Ford engines. I am still thinking its an vacuum leak somewhere and will try some soap and water and will check for bubbles.

    I did place the emergency brake on and placed the car drive the car car did not die. I think I will take the car for a spin for a 1/2 and try leaving the emergency brake on to see if the results are the same.

    My carbs do not have a dash pot. I will also look into that. Was this original to Shelby's? Hey, if it fixes my problem, I won't complain.

    Again, thanks for the assistance!

    brian
     
  2. Mike Christie

    Mike Christie Well-Known Member

    Posts:
    54
    Likes Received:
    0
    Joined:
    Jan 18, 2006
    Location:
    Colorado, USA
    Brian, If your engine is idling at 1100 RPM, then that's too high, your engine shouldn't idle any higher than a normal car. 600 to 700 rpm would be closer to normal. 1100 rpm and your transmission is engaging. Set the idle down and if it wants to die then check closely for vacuum leak somewhere like what mentioned before. I would not use soap and water because if you have a V. leak it will try to suck the liquid in and not make much difference. It you use carb cleaner or perhaps WD40 the engine will actually smooth out when sucked in giving you an indication of where it's leaking. Do you have a vacuum guage, if so. take a reading and post the figure.
    Mike
     
  3. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Mike,
    I bet my car doesn't get 7 mph. Its just horrible. Its probably due to running 1100 RPM! Heck I can through 1/5 tank just ideling and starting the car for 1/2 hour.
    Thanks for the suggestion. I won't use soap and water and will try WD40 instead. I don't have a vacuum gauge and will order one this week and will post the results. I probably won't have time to do this until this weekend, but will try sooner. I am anxious to try something new and appreciate the suggestions.

    thanks again,
    brian
     
  4. Mike Christie

    Mike Christie Well-Known Member

    Posts:
    54
    Likes Received:
    0
    Joined:
    Jan 18, 2006
    Location:
    Colorado, USA
    Brian, if you only getting 7 miles out of a gallon of gas (I'm assuming you meant 7mpg rather than 7mph) then it sounds like the engine is getting way too much fuel when idling. Even if you were actually moving down the road at 1100 rpm you would get better mileage than that, even out of a 428 c.i. You would have to be activating the other six barrels all the time. I've had both a 427 Galaxie with 2 fours and a 67 Shelby with the 428 2 fours as well and neither got that bad of mileage unless you ran wide open (which I did a few times, ahem).
    Did anyone ask if this engine has a radical camshaft installed? If it does, it could really affect engine vacuum. Also, what altitude are you at, that also will affect engine vacuum.
    Dumb question. Have you taken off the air cleaner after driving and the engine is warm and looked to make sure the chokes are fully open?
    Mike
     
  5. crzy4shelbys

    crzy4shelbys Well-Known Member

    Posts:
    202
    Likes Received:
    1
    Joined:
    Aug 20, 2007
    Location:
    Trabuco Canyon, CA, USA
    Those are excellent points. Wouldn't the fact that it idles in neutral and only has the problem when in gear eliminate the chokes being stuck shut, though?

    Josh
     
  6. Mike Christie

    Mike Christie Well-Known Member

    Posts:
    54
    Likes Received:
    0
    Joined:
    Jan 18, 2006
    Location:
    Colorado, USA
    The fact that it idles in neutral at 1100 rpm is already a problem..and there is no load on the engine. Once in gear, there is a some load on the engine and that's when the problem is compounded. I am suspicious of the carb area. Do your carbs have a bi-metalic controlled choke?
    Also, an over rich mixture would show up on a spark plug. Take a look a couple of plugs, if there black and sooty, it's running to rich.

    Uh oh, this is a big block, not so easy to get to the plugs.
     
    Last edited: Jun 2, 2008
  7. OVERRIDE

    OVERRIDE Well-Known Member

    Age:
    64
    Posts:
    223
    Likes Received:
    4
    Joined:
    Dec 21, 2004
    Location:
    elgin il
    Best way to check for a vacuum leak is a a propane bottle with a hose on it .
    if the rpm goes up you have a leak.
     
  8. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    I am fairly confident that my carbs are 4150's. Does that sound correct? Pony carburator was able to find a matching set even though my car, like any other 68' 500 came with a single carb. I am not sure if the 4150's are standard on GT500's or not.

    Yes, I believe I do have a bi metalic controlled choke on my carbs? Was this standard on the 67 GT500's? I am fairly confident that my choke is not stuck.

    I will try a propane test this weekend. I also have ordered a vacuum guage that should be here by this weekend

    I don't have a radical cam in my car and am just above sea level for elevation. Definately not a concern for altitude.

    I have lots to check and look forward with these suggestions.

    I should not that my intake manifold has two fittings. One fitting in the front where the heater hose is connected. The second fitting is at the back of the manifold that goes to the brake booster. There is actually a second nipple coming out of the back fitting that goes to my tilt away canister. That no longer works and therefor plugged the second fitting. Should I have more than two fittings on here? Just trying to supply as much info as I can

    I need to find out how to post pictures on here.

    thanks for the help
    brian
     
  9. rsimkins

    rsimkins Well-Known Member

    Posts:
    449
    Likes Received:
    7
    Joined:
    Jan 13, 2006
    Location:
    Eastcoast USA
    '67 G.T.500s came with short 4160s (no rear metering plate), list numbers 2804 and 2805 (actually '63 1/2 427 LR carbs) as standard. This was the only year that this setup came stock. The carbs sat "backwards" on the intake and had progressive linkage. The secondaries were synchronized with a vacuum tube. I'd be curious as to the list numbers on your carbs.

    The choke was bi-metallic with a long tube that ran from the left side where the choke was mounted to the front carb to the right side exhaust manifold. Hope this helps.

    Do you have any pictures of your setup?
     
  10. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    The choke was bi-metallic with a long tube that ran from the left side where the choke was mounted to the front carb to the right side exhaust manifold. Hope this helps.

    Roy,
    This is exactly what I have for a set up on my. I do have plenty of pictures. I will try to download them tonight
     
  11. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Here are the carbs that are on my car now. I can only supply one picture at a time due to the size requirements

    brian
     

    Attached Files:

  12. rsimkins

    rsimkins Well-Known Member

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

    Can you read the list numbers on the air horn?
     
  13. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Another shot of my carbs on intake manifold
     

    Attached Files:

  14. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Roy,
    I will supply them later this week when I have additional time. Again, they are not original to this engine. I believe he exchanged my original carb and one that was on my car for these two carbs that you see now

    brian
     
  15. Oregon Shelby

    Oregon Shelby Well-Known Member

    Posts:
    49
    Likes Received:
    0
    Joined:
    Jun 18, 2005
    Location:
    Oregon
    Another shot without air cleaner
     

    Attached Files:

  16. Edward66GT350

    Edward66GT350 Well-Known Member

    Age:
    61
    Posts:
    126
    Likes Received:
    0
    Joined:
    Dec 26, 2004
    When i was checking my recent brake flush and adjustment, i nailed the brakes hard and the car died and would not restart. i have a 66gt350 w/ 4 speed. any suggestions? i finally got the car to restart but only after holding the gas pedal floored and cranking. what could be the cause?
    tia,
    ed
     
  17. joesgt281

    joesgt281 Member

    Age:
    63
    Posts:
    14
    Likes Received:
    0
    Joined:
    Dec 30, 2007
    Location:
    Houston area

    based on what it took to restart it, sounds to me like a bunch of fuel sloshed out of the rear bowl as your nose was diving and flooded it.
     
  18. mikeljgt500kr

    mikeljgt500kr Well-Known Member

    Posts:
    74
    Likes Received:
    1
    Joined:
    Dec 22, 2010
    Location:
    High Mountains of New Mexico
    I just discovered this thread as my '68 GT500KR was doing the same thing after I put a new, date-coded correct 4150 Holley on it from Pony Carbs. One call to Pony Carbs solved the problem. The cathedral float (the front big screw on top with a nut under it) was not set right. I lossened the screw, turned the nut 180 degrees (1/2 turn) counterclockwise and problem was solved immediately.
     
  19. rr64

    rr64 Well-Known Member

    Posts:
    90
    Likes Received:
    4
    Joined:
    Dec 19, 2006
    Location:
    USA
    Assuming the air fuel mixture is okay (the engine isn't drowning in fuel).
    If your car has the O.E. ignition system, replace the condenser in the distributor. Back in the 1970s my Boss 302 was doing what your car is described as doing. The master mechanic at the Ford dealer explained that in my case the electrcial insulation inside the shell of the condenser was failing. The stored charges for each plug firing cycle had time to breakdown through current leakage to ground through the shell. At higher engine speeds the next cylinder got the charge before the current could escape to ground through the shell. Cheap fix was a new condenser.


    The other more recent problem has been very low quality replacement power valves. I test new valves for leak down before I install them. I was working on a friend's Boss 302 in 2008. I went to town four times to get new valves. The valve that came in the Holley brand kit was poorly machined and would not seal. (Not sealing means at idle and low speeds the engine will get way too much fuel.) I got tired of going to town to get a new Holley brand valve so on my last trip I bought every one they had of the calibration I was after. I tested a handful before I found one that worked as good as a 1960s one. I would guess I have to buy on average three or four new valves to get one that doesn't leak when it shouldn't. A 1965 GT350 owner had so much trouble finding a new Holley brand power valve that didn't leak he designed and made a test fixture for his own preuse testing.


    Good luck.
     
  20. zrayr

    zrayr Well-Known Member

    Posts:
    446
    Likes Received:
    11
    Joined:
    Oct 30, 2005
    Location:
    TX
    by your description your float was set too low and the jets were uncovered when you came to a stop.

    99% of the time the problem is the oppisite of what yours was. Holley secondary floats set to factory specs chronically overflow gas out the vent tubes, dumping gas down the venturies during a moderately fast stop.

    Z.
     

Share This Page