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Restriction plate between the thermostat housing and the head?

Discussion in 'Ocean Yacht' started by praetorian47, Aug 15, 2019 at 10:59 AM.

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  1. praetorian47

    praetorian47 Member

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    I cracked a head recently and my DD expert has never seen anything like this before. Is this normal? Do we need it or should it be removed?

    It's the second cracked head I've had on this engine.

    Attached Files:

  2. Capt Ralph

    Capt Ralph Senior Member

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    Run your serial number for the part breakdown for your engine. Determine if this plate is in that part list.

    Does your other engine have this plate?

    What HP tune?
  3. praetorian47

    praetorian47 Member

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    750hp. I can't tell if the other has it without pulling things apart. It wouldn't be on the DD parts list. My DD expert buddy was a DD mechanic and ran service for Harper Detroit up here for years. He's spoken with other old experts and nobody ever heard of them used. Our plan is to keep them but remove them.
  4. Capt Ralph

    Capt Ralph Senior Member

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    Tell more about the crack; Between the valves or water jacket over the exhaust?
    Heat or fatigue issue?
    First replacement head was used?
  5. praetorian47

    praetorian47 Member

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    2 cracks on this one, between the valves.
    I believe it's a heat issue - but I'm certain it never exceeded 200 on the gauges. I've got a murphy gauge on that engine, so when I check that it was even lower (I've never seen that hit 180 - but that doesn't mean it doesn't, it just means that by the time I run down there, it's not).
    Last year I replaced the inboard (port side head) with a new one. The one I've got to replace the other is new also. They were moving parts from the old head to the new one when they saw this restrictor and can't figure out why it's there.
  6. Capt Ralph

    Capt Ralph Senior Member

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    Between the valves IMO is fatigue.
    Mostly 4 valve heads on 92s. I have witnessed it often.
    Early this year on a 53.
    Ship Happens.
  7. Capt Ralph

    Capt Ralph Senior Member

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    What config or model is your DD engine?
    Last edited: Aug 15, 2019 at 2:09 PM
  8. praetorian47

    praetorian47 Member

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    both heads, 1 last year, 1 this year? If that's the reason, I'm good with it, just don't want to ignore a potential bigger issues.
  9. praetorian47

    praetorian47 Member

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    8v92
  10. Capt Ralph

    Capt Ralph Senior Member

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    It is a 92 head. Just making sure.
    At 750HP in a TA config,,
    Yep; fatigue..
    Not overheating.

    Your also J&T or SS?
    I'd leave that plate in then. Slows the coolant flow down just a bit, ensures the after-cooler gets max cool coolant from it's own HE.
  11. praetorian47

    praetorian47 Member

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    Thanks! so I should leave the restrictor plates in there?
  12. Capt Ralph

    Capt Ralph Senior Member

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    Yep.
  13. Capt J

    Capt J Senior Member

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    What EGT's are you running?
  14. boatpoor

    boatpoor Member

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    Anything over 180 degrees on a Detroit and you're subject to cracked heads.
  15. Capt Ralph

    Capt Ralph Senior Member

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    From experience or some readings in the cruisers nest?
  16. rtrafford

    rtrafford Member

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    Yes, this. Keep em cool, folks.
  17. praetorian47

    praetorian47 Member

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    I don't have EGT - but I'll put it in when we replace the head!
  18. boatpoor

    boatpoor Member

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    From experience. I can't start to count how many we've had to replace because of dirty or busted radiators on construction sites.
  19. Capt Ralph

    Capt Ralph Senior Member

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    I found an IPB on another web site. The plate is original.
    The picture I found is copy righted and can not be posted here.
    Yep, Keep the plate.
  20. Capt J

    Capt J Senior Member

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    In that case make sure they see around 2350 RPM's WOT. High EGT's (overloaded) can cause cracked heads in that area over the long term with the 92 series.

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