QV motor vaccum reading/ starting characteristics

Discussion in 'Technical Q&A' started by abarthracer, Apr 9, 2004.

  1. abarthracer

    abarthracer Formula Junior

    Dec 6, 2003
    Falmouth, Cape Cod
    Full Name:
    david S.
    Can anyone tell me what the vacuum reading should be at the intake plenum. I am going off of the nipple that is next to the CSI. At about 1000RPM mine is at 9.5-10 in. Seems low to me.
    Also, you guys that have perfectly running motors, what is a normal running scenario from cold. IE, it starts after 4-5 cranks, idles at 2Krpm for 3 min, then back to 1000RPM etc. I want to know if my expectations are unrealistic. And lastly, is there a base line setting for the air bleed screw under the plenum. Does it react like a normal idle speed mix screw as in use it to get the fastest idle possible and then use the idle speed screw to adjust the final setting.
    1985 QV Mondial
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  3. 4re308

    4re308 F1 Rookie

    Jun 13, 2001
    Woodstock, GA
    Full Name:
    Mitch D
    David, when my car is dead cold, it starts almost immediately and idles at 1100 right off the bat. However, after a drive during the winter, I go to crank her up, and it goes right to 2000RPM and stays there for a 1-2 minutes. I HATE when it does that. It just sounds bad to me. It think my cold start valve is no good.
  4. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    Full Name:
    Idle vacuum doesn't sound too far off. My carb'd 77 with stock cams would pull about 10 inches (with the comp cams it is much lower) at idle.

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