Results 1 to 4 of 4

Thread: Holley 600 - 80457 Tuning Transfer Circuit

  1. #1

    Default Holley 600 - 80457 Tuning Transfer Circuit

    I have a Holley 600, 80457 on my Blueprint Engines 306. The engine makes 14.5 - 15 inches of vacuum at idle. BP Engines recommends a 850 idle RPM. This resulted in the transfer slot being opened more than square. to get it the A/F Ratio in the 14:1 range, I had to have the idle mix screws turned to 1/4 turn + 1/16.

    In order to close the primary blade (correct transfer slot problem) and to get the idle mix screws to be more responsive, I opened the secondary blades a little bit. (I don't recall how much I opened the blade). When I made this change, the cruise (2800 RPM) AFR went leaner. To get the ratio to 14.5, I had to install larger main jets (from 66 - 68). The AFR is 14:1 with 69 mains.

    Overall fuel economy is around 11 MPG (city & highway at 60 MPH). I understand it will never get great fuel economy running at 2800 RPM, but the AFR at 2200 tells me it won't improve, even if I change rear end gears and get it to cruise at 2200 RPM.

    The idle mix screws are now set at 1 full turn + 1/16. The engine idle smoothly (it likes 12.5 AFR), makes 15 inHg of vacuum and has good run characteristics. I can drive the car at 1700 RPM in 4th gear and it's nice and smooth.

    The problems I have is, at 2200 RPM, AFR is 12.5 and when I accelerate, the AFR drops to 10.5. It seems the transition circuit needs to be leaned out. Can the transition circuit be leaned out on this carb considering it had press in parts that aren't really replaceable? Is there a better option to the changes I've made?

  2. #2
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    2,106

    Default

    If you feel you're close with this carb, and want to stick with it, then I'd get hold of a number drill set 1-60 and size the primary idle air bleeds, and then open them up .001" - .002" as the first step. Gary

  3. #3

    Default

    As for drilling the IABs, I'll assume I don't want drill chips to remain in the carb. I don't have access to an air compressor, but I have cans of compressed air for computers. Do you think those would clean the chips out?

    What carb would you recommend if I decide to make a change? Thanks, Bill

  4. #4
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    2,106

    Default

    Bill, I'd use a pin vice to drill the bleeds by hand. A bit a grease on the drill flutes will trap the chips. Some carb cleaner and air after to be sure. When you step up from say 70 to 72, there's not much coming out.
    Easy to step up, at small steps. Much harder to go back.
    Being the Holley website, I can only recommend you ultimately go for a later model carb with screw-in restrictors, in ALL passages, air bleeds, IFRS, PVCRs, etc.
    On my 434, I run a modified Holley XP, converted to 12 hole annular boosters, xxxxx xxx metering blocks, external PV referencing with vacuum switching, plus a few other tricks. Gary

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us