adjusting holleys

Discussion in 'The Garage' started by RootBreaker, Mar 28, 2006.

  1. RootBreaker

    RootBreaker 3/4 ton status Premium Member GMOTM Winner

    Nov 29, 2001
    Likes Received:
    Williamstown, NJ USA
    There are questions in there.. along with what I have done....
    Ok so my motor is together and I got the truck kinda going....
    first is first.... I think the choke still sucks on these carbs...
    the holley guy told me on my last carb when I called them.. he said turn the key on (to power the choke), loosen the choke cap, hit the throttle to fully open, then back off until 1/2 throttle... now watch the flies as they need to just touch closed... so turn the cap with throttle 1/2 way till that is achieved... so when I got my new holley...err couldnt do this as the fly wouldnt close that much... oh well.. will worry about that another day....

    so let see if I am right....
    front and back bowl (think I got this ok)
    loosen the top screw (just break it free) and hold the nut
    hold the screw in place and turn the nut... clockwise to go in and counter to allow more fuel in bowls...
    air/fuel screw on drivers side.... (think I got this one ok too)
    with truck running screw in clockwise until you hear the motor start to chug down then turn counter clockwise until the r's come back up...

    air/fuel screw on passenger side (not sure on if I did this right)
    this is the high rpm air/fuel adjustment right?
    anyways.. followed what I did for drivers side

    With the choke off what is a good idle rpm for a 78 chevy with a manual trans?

    so got the fuel bowls kinda adjusted (at least I think they are right...)
    adjusted the air/fuel screw on the passenger side and drivers side...
    took her out for a ride....
    ripped it onto the road but a car was in front of me.... I at least gunned it up to behind them..... and WOW!!!!!!!
    so I turned around in a school parking lot.....
    came back and no one in front of me... I nailed it and WOW!!!!!!!!
    truck now pulls in EVERY GEAR!!!!!!!
    I was like WOW!!!!!!!!
    Did I say WOW yet????
    although I still have an adjustment off on the carb though.... not sure which one.. I can nail it and im good and can feel the secondaries kick in.. however the truck starts to loose power.. not sure if the back bowl has too much or too less fuel.... and also I believe the passenger side air/fuel screw is the high rpm adjustment????
  2. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

    Nov 14, 2005
    Likes Received:
    Kzoo, Mi
    The bowls should be adjusted to provide a level at the bottom of the side bowl plug (this is called the level sight plug) remove that and put in a clear plug. While the engine is running (be careful not to make a quick adjustment) loosen the screw and adjust the nut until the level is even with the bottom of the plug. do this for both bowls. The mixture adjustment screws on each side of the carb, do the same thing. They should both be tuned together (same amount for each side) They just control the amount of mixture at idle for each side of the carb. The higher rpm mixture is controlled by jets, air bleeds, power valves etc.

    A good book to get is How to tune Holley Carbs. I've used it a lot.

    Good luck, sounds like your going in the right direction.

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