1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Rejetting a Holley

Discussion in '40- & 55-Series Tech' started by Wheelin4, Jul 11, 2005.

  1. Wheelin4

    Wheelin4

    Messages:
    55
    Likes Received:
    0
    Joined:
    May 16, 2005
    Location:
    Up 4
    I have a Holley Truck Avenger carb on a Chevy 350 with a mild cam and HEI. I have recently moved to 4200 feet in elevation and need to rejet as my rig is running super rich. Here is my dilemna/question. If I spent all of my time at 4200 feet the rejet would be pretty straightforward as Holley recommends jetting down one size for every 2000 feet in elevation. The problem is that most of the wheeling I do is at 6000-9500 feet and I need to drive to the trail which can involve highway time at sea level.

    Any recommendations on where to start? Main jets on the Truck Avenger are 68 and secondary jets are 89. For what it's worth, the motor runs slightly rich at sea level with the stock jetting. If I jet for say, 6000 feet as a compromise will I do damage to my motor at sea level?

    Lastly, will I need to make any other adjustments aside from jets and possibly the idle mixture?

    Sorry, but carb tuning is new to me and fuel injections isn't in the budget. . .

    Thanks!
     
  2. Wheelin4

    Wheelin4

    Messages:
    55
    Likes Received:
    0
    Joined:
    May 16, 2005
    Location:
    Up 4
  3. Rice

    Rice SILVER Star

    Messages:
    4,626
    Media:
    10
    Albums:
    1
    Likes Received:
    5,735
    Joined:
    May 2, 2003
    Location:
    GSO NC
    You don't mention fuel pressure so before making mention of jets are you using an electric pump? If so is the pressure at or below 5-6 psi? If the pressure is too high then the needle valves fail to close and fills the bowls in which case the metering system will no longer meter correctly.

    For the record, what size carb is this?

    Once you're sure the pressure is ok ... regardless of the jet you pick just be sure you don't let it run lean. Especially if you run cast pistons. That said, if you already know it's running rich even when at sea level then dropping 2 sizes would be a good first step. If still a little rich there will be a slight drop in power, plugs foul a little sooner, and you'll have to blow the carbon out a bit more often but at least you won't burn a valve or piston.
     
  4. Wheelin4

    Wheelin4

    Messages:
    55
    Likes Received:
    0
    Joined:
    May 16, 2005
    Location:
    Up 4
    Thanks. I am running an electric fuel pump but haven't checked the pressure. It is a 670cfm Truck Avenger carb. I spent a half hour on hold with the Holley tech line this AM before giving up.