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Technical Got a "What-If" question about flat head Fords.....

Discussion in 'Traditional Hot Rods' started by 6sally6, Sep 20, 2018.

  1. 6sally6
    Joined: Feb 16, 2014
    Posts: 768


    While mowing my lawn today I thought........" were most flatties zero decks....or were the pistons "in-the-hole" a little? I know it was common practice to mill/shave the head down to gain compression but....with the valves in the block it also hurt the breathing ability to shave'em.
    IF the blocks deck could be zero that might help CR without pinching the valve clearance...right? May need to cut an equal amount from the valve stems to restore valve seal hmmmm?!......................oooops, time to turn around and mow another row.
    So, were they zero deck?
    paintslinger805 likes this.
  2. Fortunateson
    Joined: Apr 30, 2012
    Posts: 2,361


    Well I'm no expert but if you shaved the block merely shortening the valve stem wouldn't do the job. I would think that the valve pocket would have to be reground the same amount wouldn't it?
  3. dan c
    Joined: Jan 30, 2012
    Posts: 1,906

    dan c

    i think you're talking domed pistons vs. flat tops?
  4. 97
    Joined: May 18, 2005
    Posts: 1,483


    The only "universal cure all " is extra air pressure!! Satisfies both ends of the equation.
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  5. 2E26DE87-AC42-4E19-A32F-2BEF43A0F69F.jpeg 757CCE5A-04AD-47B0-8180-FE78735AA4F1.jpeg Flatheads have a “thin deck” to start with and should NOT be cut unless they are not flat. Also the angle of the valves(in relation to the crank) on each bank differs from pass side to drivers side and some perfectionists want to try and make these angles the same. Not a good idea as the amount of Cc’s per side is not vastly different and not worth the trouble and expense to try and make equal.I have built over 25 engines for myself as well as customers and lately have made the relief about .125-.150 deep only on the intake side because my thinking is the exhaust is expelled under pressure and is not needed all the way across the transition area. Only a dyno test can tell the diff from a full relief and a partial relief, but “seat of the pants” feel very good. Flatheads Forever! My 32 cabriolet runs 80 in the 1/8 mile with a 289 in Flatmotor.
    jim32 likes this.
  6. The drivers side deck is taller from factory. If you want a square deck you have to match deck height on both sides. If you mill down the heads you should check and make sure the valves don’t hit the head. Might even re cut/relive the valve pockets. And check the piston to head space. I milled my heads .030” to get a .040” squinch between piston and head dome, the magic number... And also my block was “squared” both deck heights match. Only need to it if you want a true blueprinted motor!!! Ie- racing motor.
  7. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,452

    Bandit Billy

    Mine are quite a ways down in the hole:cool:
    Rick Hegdahl and CME1 like this.
  8. Rick Hegdahl
    Joined: Dec 13, 2017
    Posts: 15

    Rick Hegdahl

    Nice polish in those ports!
    Mine was rebuilt by previous owner and when i had the intake pulled, i saw that mine were only ground for the gasket; no polish.
  9. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,452

    Bandit Billy

    I got after that flathead quite a bit. Strong running motor!
  10. R Pope
    Joined: Jan 23, 2006
    Posts: 3,310

    R Pope

    The decks are different side to side because the crank and cam are offset to one side. This was Henry's way of reducing piston slap, where most other engines use offset wrist pins.
    deucemac and Cyclone Kevin like this.

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