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Engine Hesitation--Need Advice

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by cleszkie, May 30, 2001.

  1. cleszkie

    cleszkie 1/2 ton status

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    Need some advice on diagnosing my engine problem. I run a 350 small block with an Edelbrock Performer intake and matched Edelbrock 4-barrel carb, headers, and a Mallory Unilite distributor and coil (TH350 tranny). My problem is this: The engine runs fine at normal loads and speed and at idle. However, when the hammer is dropped it stumbles a bit. Sounds like a fuel delivery problem. I do run a stock fuel pump, and have already replaced it once (filters too). This problem increased when I went to Big Bear last weekend, so I thought that I might be running a bit rich since the symptoms increased at a higher altitude. Anyways, looking for advice. Do I check the timing, adjust the fuel/air mix, or look into a high flow fuel pump?

    Any thoughts appreciated.
     
  2. ChrisM72beast

    ChrisM72beast 1/2 ton status

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    Hey, I'm no expert but I've had the same problem from time to time. It might be just that your carb needs to be adjusted. Especially if it's fine except when you floor it.
    Good Luck
    Chris
     
  3. Steve_Chin

    Steve_Chin 1/2 ton status

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    If you are running a pretty stock camshaft, the Edelbrock AFB clone is probably too rich. My Blazer had an Erson 270 cam in it when I bought it and an Edelbrock AFB clone and I could feel that it was too rich. I changed that out for a Quadrajet and a Performer RPM Q-jet intake (previous intake was a square-bore Performer RPM), played with the jetting, and gained a lot of top end plus better fuel economy. I believe that Edelbrock offers jetting kits for their AFB clone, so you can get the parts from them so you can custom-tune your carburetor.
     
  4. Klef72K5

    Klef72K5 1/2 ton status

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    You need to set your timing first. Then you can adjust the carb. What size of carb. did you put on?

    <A target="_blank" HREF=http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg>http://wsphotofews.excite.com/031/rw/Jo/og/t488200.jpg</A>
     
  5. olbluebeast

    olbluebeast Registered Member

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    i know this all too well. it was as simple as a new borg-warner custom plug wire set. it is between 30 and 40 bucks. also replace your plugs. for a few extra dollars you will be surprised how well the various split fire plugs improve performance. try this first, and you may be surprised. next set your timing. if your truck pops lightly once after you turn it off, then you are running too rich of a fuel mixture. also smell your exhaust believe you me you can smell a rich mixture, very sweet gassy smell, like unburned gasoline. first off i would go the plug wire route, it really did the trick and i had a the same problem you had under a load. make sure the wires are all pulled far enough away from the block, if the touch they block they will short. hope it works for you.
     
  6. cleszkie

    cleszkie 1/2 ton status

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    Thanks for the input. This definitely sheds some light on the problem. The symptoms all seem to point to an overly rich mixture. I am running a stock cam, and my carb flows 600 cfm. I have seen the jetting kits offered by Edelbrock, and will probably persue a leaner setting in this way. I think I will also change the plug wires, as they are getting kind of on the old side, and do not really fit the Unilite distributor very well anyways.
     
  7. Ryan_B

    Ryan_B Registered Member

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    And how about that accelerator pump?
    ... usually there's about 3 different settings you can move the accelerator pump to. Sounds like you might want to try that, since it's damn easy to adjust.
     

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