schillazschillaz Posts: 287Expert Adviser
Does anyone know if this is a hudson piston? I've never seen one like this. Interesting!


  • GeoffGeoff Posts: 3,956Senior Contributor
    I've never seen one like that either. I certainly cannot see any advantage of such a design.  
  • HansHans Posts: 101Senior Contributor
    perhaps some one had 2 cycle outboard motor experience.

    Various types of shapes have been used to deflect combustible mixtures as well as increasing compression.

    Someone may have realized the shape of the cyl head space could be used to do both, raise compression and improve flow turbulence for better combustion.

    An interesting concept to think about.

    I personally have milled Essex cyl heads .127 and more. 
     At .127 the clearance for passage from valve pocket to piston (including gasket) was very tight. However the compression was increased substantially, estimate from 5.7 to aprox 8.3 cr.

    We should recall the Essex engines used Ricardo  shaped cyl head cavities to gain better volumetric flow so a higher cr and improved combustion could be utilized/ obtained.
  • HansHans Posts: 101Senior Contributor
    With the large valve pocket on Essex heads I think the possible use of "padding" as used on engines to increase cr ratio is a possibility, keeping in mind  cyl head hot spots vs cooling.

    Clerances vary from valve faces to head/gasket face is significent, for each Intake and 
    Exhaust valve.

    There certaily could be room for improvement..........

  • schillazschillaz Posts: 287Expert Adviser
    That's what I was thinking. Someone cast their own pistons back in the day, but figured I should ask incase someone has seen them before. Trying to get the engine casting numbers now for some more info on the block. Will update when I have the info.
  • bob wardbob ward Posts: 1,170Senior Contributor
    edited June 18
    Interesting. Possibly the thought was to improve combustion by directing 2 jets of combusting gases, one each side of the lump, into the space above the piston.
  • terraplane8terraplane8 Posts: 543Senior Contributor
    Strange as the lump would appear to shield the combustion chamber from the spark plug which I assume is placed over the valves.
  • dave11dave11 Posts: 141Expert Adviser

    My guess is this may have been an experiment to raise the compression with out drastically modifying the cylinder head?

    It would be interesting know how it performed

  • schillazschillaz Posts: 287Expert Adviser
    casting on the block below the distributor is:


    So I believe it to be a 54 308 block. It doesn't look like 2 in valves to me. (cant get a measurement yet)
  • Ric West INRic West IN Posts: 482Senior Contributor
    Yes, 310111 is a 1954  308 block.  Which foundry?  CWC, WF, or  ?
    Could the 0 in the date code be a D ?  CWC used a letter for the month, A = January B is Feb. 
  • schillazschillaz Posts: 287Expert Adviser
    Its CWC so must be a D.  thanks
  • superwaspsuperwasp Posts: 36Member
    Schillaz, are you going to try to use them? I think we're all really curious how they'd perform.
    I've seen performance flathead Ford pistons with a depression in that same area, but being a depression rather than a dome, that's obviously the inverse concept. 
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