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Thread: Please Help with Street Avenger 770

  1. #1

    Default Please Help with Street Avenger 770

    Hello all. I have a question and hopefully someone can answer. I rebuilt my carb a few days ago and I cannot get this thing to run good at all. Little about my engine:
    454 Mark IV
    Mild street cam: .515"/.520" duration @ .050" 224°/230° Lobe 110°
    Torquer intake manifold
    Stock oval iron heads. 2.02"/1.77"
    Mallory Unilite Mechanical advance
    Accel coil

    I had place the wrong meter gasket on. Engine ran bad, fixed the gasket. 6.5 Power Valve blew, changed to a 4.5 (because I had one). Now, My vacuum was low at 10 inHg when I got this car. Talking with someone, they help me adjust the secondaries to get more vacuum. At 14 inHg now. Car idles good around 800 on idle, around 700 in gear. Timing was at 20° initial/40° top, but have to bring that back down. Car overheated on test run. Engine seems to like 14-16° initial; 32-36° top.

    Now today when I screwed in the passenger side mixture screw all the way in, the engine didn't even budge. I closed the mixture and started to close the drivers side. Engine started to lower its idle, but never shut off. Both mixture screws closed, engine is put putting on. If I leave the passenger side open and close the drivers side, engine barely changes idle. I do not think this is right. Am I wrong? Car is blowing black smoke and smells rich in gas. New PV installed today and still same symptoms. I'm hoping someone can chime in. Had someone knowledgeable try & help, but he cant figure it out either. Thank You in advance.
    Last edited by morrongafish; 03-13-2019 at 08:08 PM.

  2. #2
    Join Date
    Jan 2010
    Brisbane, Australia


    You need to take the carb off, and observe how far open ALL of the throttle blades are. No response to mixture screws points to the blades open too far. What was wrong with the carb before your rebuilt it? Gary
    Regards, Gary

  3. #3


    Thank you for your reply Gaz64. Yes, I agree with you. After researching last night and thinking about it, the passenger side throttle blade does expose the transfer slot a lot more than the drivers side throttle blade. This is having the drivers side transfer slot open at a square. I have a feeling that the throttle blade might be bent.

    I bought this car about a month ago and have been doing the look over and fixing the problems it has. The fuel system was installed incorrect on this car. They had a Mallory 4207 (non-bypass) regulator being used as a bypass/return fuel system. I purchased a correct fuel pressure regulator and installed it. Car also had two of those plastic fuel filters on the car and they looked like they have not been replaced since Jimmy Carter was in office. I installed a 100 micron filter between tank and pump (Mallory 110) and installed a 30 micron from regulator to carb. Eventually will change to a 10 micron. Fuel psi is at 6.

    So to answer your question, I rebuilt the carb so that I would know that insides were new. Carb is pre-92, was leaking out of a few areas, PV was bad, and my vacuum was at 10 inHg. I figured I had to have a vacuum leak somewhere. Carb spray test wast not concluding a leak, nor is now. At 14 inHg now, brakes do feel MUCH better.

    But I'm pointing this one to the throttle blades for now. I read that if the transfer slots are too exposed, it will make the car run rich and smoke out of exhaust. Right now, that is the only problem. Car idles great and does not shut off. Only other thing is that it has a little bog when you hit the gas, but that I can adjust after I fix this issue. If I missed anything, I'm all ears on this subject.

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