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Technical checking floating rod bearings

Discussion in 'The Hokey Ass Message Board' started by fftoddster, May 15, 2019.

  1. fftoddster
    Joined: May 31, 2010
    Posts: 67


    I have a 37 Ford flathead that was burning oil and needs to be freshioned up.
    I have read the a lot of times the bearings can be reused.
    My question is other than a visible check should I plastigauge them before I pull engine apart? (I don't have mics) since the are floating do you plastigauge both inside and outside of the bearing?
  2. 28dreyer
    Joined: Jan 23, 2008
    Posts: 1,085

    from Minnesota

    Forget the Plastigage.

    You need to use a micrometer to exactly measure the crank pin diameters and assemble and torque the rods and caps without the bearing shells and measure preferably with a bore gage or inside micrometer.

    Compare readings to engine specifications to determine what size bearings to use or if you are in need of crankshaft grinding and/or connecting rod re-sizing.
    Last edited: May 16, 2019
    302GMC and dirty old man like this.
  3. Plastigage is a good place to start. Yes you would do both sides of the insert. If your in spec move on if it's just an overhaul. If your oil pressure is holding solid at around 10-15 lbs your probably Golden. If your a Shop and doing a Customer job then of course your going to do a Total tear down, do a bore job and do a total rebuild by the book. I mean ya gotta guarantee your work out the door, not just under your own Foot. That machine shop rebuild will hit your Wallet some where between 7K and 10K depending on how much you let them do. You can bring it back to good enough at home under 2K. Maybe less if your just doing Band-Aids.
  4. morac41
    Joined: Jul 23, 2011
    Posts: 496


    28 dreyer is on the money I have rebuilt a lot of these fully floating motors back in the need good micrometers both internal and external ...a lot of patience and write every thing you measure down as you are dealing with several measurements ie; internal of the con rod ..crank journal...thickness of bearing the clearance..just take your time and recheck ...personally I wouldn't use Plastigage...its a very expensive mistake if the engine fails...The clearance is very critical to avoid bearing failure ...just be very patience..check check again
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