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Hot Rods Which Rings to Use on Ford OEM Flathead Steel Pistons

Discussion in 'The Hokey Ass Message Board' started by A BONED, Mar 22, 2017.

  1. A BONED
    Joined: May 9, 2008
    Posts: 325

    A BONED
    Member

    I bought a 59A flathead that was used as a stationary generator it's whole life, it was supposed to be a great running motor. I pulled the heads to take a look at the bores, all bores look good, there is no lip at all on any of the cylinders, the thing is standard bore 3.1875' (3-3/16'). After cleaning off the tops of the pistons I found that one piston has a very small section missing on the edge of the dome, exposing the top piston ring. Another piston had a crack about an inch long, extending down to the edge.

    The block looks to be a '39 Mercury 239, it has a 46-48 crab distributor and Ford 59A heads. Apparently this was not uncommon for a stationary / commercial engine at the time. I'm no expert, I don't really know if this is true or not. I believe the pistons in it are steel, 3 ring, standard bore P/N 99A-6110-A. I can get my hands on a couple of slugs, I was hoping to swap these out with a new set of appropriate rings, and hone the cylinders. I have included images of the tops of the pistons, and the block deck surfaces. Any advice on pistons and rings to use would be great. Thanks.

    Chris.
     

    Attached Files:

  2. flatjack
    Joined: Feb 13, 2007
    Posts: 975

    flatjack
    Member

    I see no sign of any sleeves. Did you check the pistons with a magnet?
     
    Hudson31 likes this.
  3. A BONED
    Joined: May 9, 2008
    Posts: 325

    A BONED
    Member

    No sleeves Flatjack, the pistons are definitely steel.
    Although I will go home and try the magnet test tonight, thanks.
     
  4. 58custom
    Joined: Jan 1, 2009
    Posts: 398

    58custom
    Member

    A question: is it normal for such a stock block to be relieved?
     

  5. A BONED
    Joined: May 9, 2008
    Posts: 325

    A BONED
    Member

    58custom, I believe it's '39 Mercury block that was use as a commercial / stationary generator. It's not unusual for these to be factory relieved to cope with detonation issues...

     
  6. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    I have seen a few like that. All stationary engines, which would be left to run for long periods, without supervision, and with minimum maintenance. You can see that it was done entirely by machine, given the precise nature of the cuts. No sign of the hand-of-man.

    Although that one looks like it has only about 135-hours on it!

    Even so, I think I would track down some aluminium alloy slugs.
     
  7. A BONED
    Joined: May 9, 2008
    Posts: 325

    A BONED
    Member

    gimpyshotrods, how do we know it's done 135 hours work...?
     
  8. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    The last engine that I pulled apart for inspection and leak repair had 135-hours on the meter. It looked just about the same inside, except it was just TWO YEARS OLD!

    How that one looks that good at 78-years is a miracle. That is quite the score!
     
  9. A BONED
    Joined: May 9, 2008
    Posts: 325

    A BONED
    Member

    gimpyshotrods, I thought you may have had a crystal ball over there...
    Nice observation, I was told that it had done very little work since new
    You definitely think I should just get some decent alum slugs and rings, and rebore?
     
  10. Kan Kustom
    Joined: Jul 20, 2009
    Posts: 2,739

    Kan Kustom
    Member

  11. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    If you even need to bore it. Measure the bores, and inspect them carefully. If a hone job is all that it needs, just do that. No point in reducing service life and spending money for no reason.

    I do recommend something other than steel slugs. Whenever possible, I like to take as much unnecessary weight out of the rotating assembly. A steady state, governed stationary engine will do just fine over time with a heavy slug. You, presumably, will be putting this in a car or truck, where you will need to have it rev-up, with a fair degree of responsiveness. The heavier the rotating assembly, the slower it will rev-up.
     
  12. A BONED
    Joined: May 9, 2008
    Posts: 325

    A BONED
    Member

    Thanks man, good advice. I have an Isky 1007B cam and adjustables coming as well. I figure I could mill the heads for a little more compression fit the cam and lifters, hone the cylinders and re-ring the pistons and also check main and rod bearing. Hopefully I can cut some laps with the lads. Looking to go AV8 on my 29 roadster, and not miss out on another season.


     
  13. drtrcrV-8
    Joined: Jan 6, 2013
    Posts: 1,707

    drtrcrV-8
    Member

    Might be a good idea to balance the assembly(including the flywheel/clutch), as you're changing the internal weights of the pistons. Re-balance is always a good idea, as it makes for a longer lived/smoother running engine.
     
  14. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Always balance.
     

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