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Technical Ignition retard under boost

Discussion in 'The Hokey Ass Message Board' started by seb fontana, Dec 15, 2025 at 6:34 PM.

  1. seb fontana
    Joined: Sep 1, 2005
    Posts: 9,201

    seb fontana
    Member
    from ct

    Nowadays I read about boost and ignition retard is required. I realize todays world is different with quite a few lbs of boost FI and computers but what was done in the old days, pre '65? Ford had supercharged option in '57, Stude in early 60's; did they have ignition timing retard? What if we go back even before '57 there were quite a few cars that had superchargers, Gram, Cord. Plus in the late 50's there was Paxton type kits so where is the point of boost to needing ignition retard?
     
  2. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 3,972

    19Eddy30
    Member
    from VA

    Yes on some , & No On some ,
    Octane was much higher and had four or five different octane ranges on pump gas.
    Some learn to have A distributor
    "locked out some Not " distributor base loose with springs attached to it Full Advance, and a cable attach to distributor " Pull Cable " To retard timing under boost,
    Release cable back to full advance .
    1 to 1.5 deg's of retard per 1 psi
    & also depends on static Compression
    & boost , A 9:1 engine with 4ish No retard needed most on 91-93 oct.
     
    Last edited: Dec 15, 2025 at 6:55 PM
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 59,980

    squirrel
    Member

    Yes, it depends on a lot of things. I never ran boost retard in Plan II, it had about 8.5 compression with a 6-71 and ran fine on pump gas with up to 38 degrees advance in the 427. About 6-8 psi boost.

    I think you'll find the engines in those old supercharged cars had low compression and low boost, and also not enough carb or cam to let in enough air to make much cylinder pressure.

    The turbocharged Olds in the early 60s had water injection, but also not much boost.
     
    pprather likes this.
  4. saltflats
    Joined: Aug 14, 2007
    Posts: 13,600

    saltflats
    Member
    from Missouri

    I believe some of those had a vacuum advance/retard it would retard with a boost signal.
     
  5. miker98038
    Joined: Jan 24, 2011
    Posts: 1,589

    miker98038
    ALLIANCE MEMBER

    I’m pretty sure the F code had a vacuum can that did some boost retard. On my blow thru F Clone, and the SN series on my bird, I used an MSD, a Hobbs switch, and 2 degrees at 3lbs. I know that’s cheating, but easier in today’s world. Had Chevron Supreme or Sunoco 260 from the 60’s been available I probably wouldn’t have needed it.

    Those were 5-8lb engines.
     
  6. 38Chevy454
    Joined: Oct 19, 2001
    Posts: 6,788

    38Chevy454
    ALLIANCE MEMBER

    I think the amount of boost 5-7 psi wasn't enough that boost retard was needed as compared to today 14-20 psi typical. Add in carbureted that was probably a little on the rich side to also be bit forgiving. Plus the higher octane fuel inherently more detonation resistant.
     
  7. HEATHEN
    Joined: Nov 22, 2005
    Posts: 9,045

    HEATHEN
    Member
    from SIDNEY, NY

    My Corvair Spyder had a combination vacuum advance/retard mechanism.
     
    saltflats likes this.
  8. saltflats
    Joined: Aug 14, 2007
    Posts: 13,600

    saltflats
    Member
    from Missouri

    That is what I remembered.
     

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