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Quadraboggin' at low RPMs

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Blazer_Boy, Apr 29, 2002.

  1. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Quadraboggin\' at low RPMs

    Sorry for posting a bizillion times on this, but I think I got an idea of whats up here. 355 motor has vortec heads, edelbrock performer intake and .447/.462 210/218 111 seperation cam advanced 4 degrees. The basic deal is that it does not like throttle at low RPMs. It idles great and all that stuff, but I have to have wound up to get any throttle response. Try giving some gas right after I shift to second and nothing. You can baby it up to speed and then I'll be fine. I was thinking that spring for the power piston in the Q-jet maybe too stiff and I don't have enough vacuum to make it work properly. Whats a good primary/secondary rod and jet combination too, or is stock fine?
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Quadraboggin\' at low RPMs

    Sounds like a bad accelerator pump to me.

    Rene
     
  3. Jay73K20

    Jay73K20 Registered Member

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    Re: Quadraboggin\' at low RPMs

    I almost have the exact same combo, .060 bore is the only difference. You should be developing around 14 to 16 in lbs of vacuum at idle. Also I usually cruise with 9 to 12 in lbs of vacuum. It sounds like you are developing a hesitation during power mode mainly. If you floor it right off the bat she hesitates doesn’t she. I’m surprise idle isn’t too lean also. I had the same problem with my EDL 1406 until I richen her out a lot but she still hesitated transiting to WOT. I supposed I could have richened the secondary jets even more but I already went 8 percent richer with no change so I said screw it. I ended up having my 800 CFM Q-jet rebuilt by Jet Performance and I love it. I wished it were a 750 CFM instead because the primary ventires are 50 CFM smaller for a crisper throttle response but I didn’t know the difference until after the fact. Plain and simple you need to richen the carb. Before I had my Q-jet rebuilt I slap on an original 86,000 mile Q-jet off a 71 C10 350 which is rated about 240HP stock, needless to say it was way to lean all modes. It also helps to have an O2 sensor with gauge to read your engine and a vacuum gauge. As for the primary metering rod spring the stronger it is the faster it will pop the metering rod up out of the main jet which richens the mixture, meaning you need more vacuum to be in cruise mode which is opposite of what you’re thinking.
     
  4. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: Quadraboggin\' at low RPMs

    I think I'm gonna bite the bullet and have it rebuilt by a local guy. He's kinda the name that everyone says when you ask about getting a carb done. I'll write back what he says. It was alot warmer today and it sure worked alot better. I still want the piece of mind of having someone set it up along with the overhaul. How do you like your motor so far? I can't over the fact that I chirp the tires by barely trying and with an out of whack carb too.
     
  5. Jay73K20

    Jay73K20 Registered Member

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    Re: Quadraboggin\' at low RPMs

    I love it, cheap and powerful. I'm runnig 4.10 with 35's and I'll light the one up at a stop when ever I want to. good gas milage to.
     
  6. MudbogAD

    MudbogAD 1/2 ton status

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    Re: Quadraboggin\' at low RPMs

    yea, it does sound like an accelerator pump.
     
  7. Blazer79

    Blazer79 1/2 ton status

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    Re: Quadraboggin\' at low RPMs

    On your Q-jet there's a vertical rod that moves the accelerator pump lever (like a see-saw) on top of the carb. First try to move the vertical rod to the other hole and see if it improves. If it still hesitate, try bending that see-saw looking lever to a straighter angle (closer to 180 deg) to lean it or close it to 90 deg to enrichen it.

    Hope this helps.
     

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