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  •  » 347 failure.

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    6/11/2026 1:43 PM  #1

    boss347convertible
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    Registered: 4/22/2013
    Posts: 191

    347 failure.

    After 22 years of use, the 347 in my 66 failed while on tour. Driving from Huntington Beach to Carmel, approximately, 125 miles into the trip, cruising approximately 65 in overdrive, a loud cracking noise came on and I immediately pulled onto the shoulder. I called a tow truck and while waiting for 5 hours, removed the driver's side valve cover and all looked normal. Had I pulled the passenger side valve cover, I would have seen part of the problem, but decided to wait as I knew the engine would not be running.

    Next day, things started to become clearer upon dissasembly. I tried to post photos, but without success, so I will just explain that a valve either broke, struck the piston or a combination of both.

     

    Last edited by boss347convertible (6/11/2026 1:46 PM)

     

    6/11/2026 2:59 PM  #2

    Rudi
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    From: Stuck in the 50's Welland Ca
    Registered: 4/01/2013
    Posts: 4,106

    Re: 347 failure.

    Sucks to hear that!
    How many miles on it?

    Good work ain't cheap, Cheap work ain't good!
     

    6/11/2026 3:10 PM  #3

    Steve69
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    From: Madison Wisconsin
    Registered: 4/01/2013
    Posts: 2,821

    Re: 347 failure.

    Sorry to hear that.  22 years is a good run.  How many miles did you have on it?  Whats your plans to replace your engine?

     

    6/11/2026 3:18 PM  #4

    boss347convertible
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    Registered: 4/22/2013
    Posts: 191

    Re: 347 failure.

    Miles are in the 80-90k range. Mostly hard/fun miles. I have no complaints. Replacement engine will be a 363 that I will detail in a separate post.

       •Thread Starter
     

    6/12/2026 5:16 AM  #5

    BobE
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    From: White Plains, NY
    Registered: 4/04/2013
    Posts: 3,043

    Re: 347 failure.

    Sorry to hear about the failure, good luck with the new enginee. 

    65 Fastback, 351W, 5-speed, 4 wheel discs, 9" rear,  R&C Front End.
     

    6/12/2026 8:03 AM  #6

    RTM
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    From: Cape Coral FL
    Registered: 5/22/2019
    Posts: 2,154

    Re: 347 failure.

    Sorry to hear that but it did last a good spell and sounds like it provided a lot of fun along the way.

     

    6/13/2026 5:41 AM  #7

    Nos681
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    From: Atlantic Mine, Michigan
    Registered: 7/14/2016
    Posts: 3,586

    Re: 347 failure.

    Sounds like new engine will be fun too.

     

    8/06/2026 3:28 PM  #8

    boss347convertible
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    Registered: 4/22/2013
    Posts: 191

    Re: 347 failure.

    Photos.








       •Thread Starter
     

    8/06/2026 3:36 PM  #9

    boss347convertible
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    Registered: 4/22/2013
    Posts: 191

    Re: 347 failure.



    The valve stem sheared.

       •Thread Starter
     

    8/06/2026 6:00 PM  #10

    6sally6
    Hyper FYIFORD ADDICT

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    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 7,032

    Re: 347 failure.

    How did the block look ? Did you save any pieces for future use ?  Hate to hear the bad news....
    6sally6

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    8/06/2026 6:32 PM  #11

    boss347convertible
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    Registered: 4/22/2013
    Posts: 191

    Re: 347 failure.

    At least one cylinder would require sleeving. It has a forged crank and if the rods are straight, there are a lot of good parts. i’m going to put it up for sale and I’m guessing that someone will rebuild it.

       •Thread Starter
     

    8/07/2026 5:08 AM  #12

    RTM
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    From: Cape Coral FL
    Registered: 5/22/2019
    Posts: 2,154

    Re: 347 failure.

    Someone will buy the left over good pieces for sure.

     

    8/07/2026 9:24 AM  #13

    wsinsle
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    From: Belle Vernon, PA
    Registered: 4/01/2013
    Posts: 1,812

    Re: 347 failure.

    No time is a good time for something like this. With 22 years and over 80K hard miles, don't sound like a build problem. Hope you get at least that out of the next one.

    If this forum can't fix it, it isn't broke.
     

    8/07/2026 10:07 AM  #14

    rpm
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    From: Bakersfield, Ca
    Registered: 9/17/2013
    Posts: 3,961

    Re: 347 failure.

    Thanks for the update Mike.

    Bob. 21.5 freeway MPG 69 Mach 1, 5.0 GT40P heads, SMOD Toploader, Armstrong  steering, factory AC
     

    8/07/2026 10:54 AM  #15

    Glens 1965 50
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    From: Tomball,Tx
    Registered: 4/01/2013
    Posts: 297

    Re: 347 failure.

    That sucks.

     

     

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