If not for bad luck I'd have none....finally got boat working and Big block goes boom

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by WetPleasure, Sep 21, 2021.

  1. WetPleasure

    WetPleasure Member

    101
    Jan 30, 2021
    99 260 sundancer
    7.4 bravo3
    Show me where any.of those guys offered any actual advice prior to my rebuild......I'll wait.

    Scofflaw did agree with me when I was refuting another member who didn't think I will get more RPMs.out of the rebuild. Other than that, there was no real advice offered to me on how to go about this rebuild. That was fine, I took it upon myself to do a lot of research in other avenues. I simply came back here to give a update a s of course now after the fact and my motor is done all these people.have opinions on what should have been done lol, it's comical!
     
    Last edited: Dec 1, 2021
  2. Pirate Lady

    Pirate Lady Well-Known Member

    Jun 2, 2020
    Chesapeake Bay, Middle River
    '91 250 Sundancer
    7.4 Bravo 1
    Good luck with finding a 7.4 from what i hear, i baby mine. Used are impossible to find, so i hear. Been told Jasper cant get them.
     
  3. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    I get pretty heated myself sometimes. Good thing is, it's the internet. Who really gives a shit? Good luck with whatever you wind up doing.
     
    Nater Potater and techmitch like this.
  4. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    Nah. You just have to know where to look. Junk yards are still full of them. Certain 96-01 Chevy vans will have one for instance. Same motor, but would need a cam for starters. I have two long blocks sitting in my garage that I picked up for $500 with an extra set of 290 heads. I'm going to build them just because.
     
    techmitch likes this.
  5. techmitch

    techmitch Well-Known Member PLATINUM Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    Well, here's on for ya. Tom told you the pistons that you installed are designed and manufactured to meet best clearance specs. when hot. Guess what? Boats run cold comparatively speaking... for more reasons than you can waste your time "researching"
     
  6. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    But GM 4 bolt main blocks are getting rare. However, you can still purchase a new World Products Merlin BBC block which are actually a stronger casting than what GM offered. Close to $3K but if you are going to invest in a solid basis the right way to go.
    http://www.pbm-erson.com/Catalog/World-Products/Blocks-WP/Big Block Chevy
     
  7. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    I hear people say that, but I still see them all over the place. I have four Gen 6 L29s so I'm all stocked up for now thankfully. One in the boat, two in the garage and one in my 69 Camaro.
    Merlin would definitely be a nice way to go if you needed to!
     

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    Last edited: Dec 1, 2021
  8. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    Truck blocks? Grab em and hold on to em - they are rare around here.
     
  9. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    Just popped into the marketplace and did a quick search. This would be a great deal for somebody...

    Screenshot_20211201-212935.jpg
     
    Mauler34Rod and ttmott like this.
  10. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    It's worth noting for others that many parts cannot be exchanged between the Mark IV and the Gen V and Gen VI BBC engines. Crankshafts are different, seals are different, and there are challenges swapping heads......
     
    Mauler34Rod likes this.
  11. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    Heads are a non issue now. You just need the right head gaskets if you want to put Mk IV heads on a Gen VI 454. Gen VI motors just have a far superior block. Not to knock Mk IV, but that's just how it is.
     
    Mauler34Rod likes this.
  12. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    You are right about that!
     
  13. HawkX66

    HawkX66 Well-Known Member

    Jul 27, 2020
    SE Virginia and NH
    "Tread Knot"
    1997 Sea Ray Sundancer 290DA

    2020 F350 6.7L
    454 L29 Carb w/ Bravo III
    I love my big blocks...

    20180501_204516.jpg
     
    PlayDate and ttmott like this.
  14. WetPleasure

    WetPleasure Member

    101
    Jan 30, 2021
    99 260 sundancer
    7.4 bravo3
    1. He made that statement today also known as AFTER my motor rebuild has already been completed.
    2. It's horseshit advice. He talks as if there are no marine engines with forged Pistons! There are thousands of them!!
     
  15. ttmott

    ttmott PhD in OCD TECHNICAL Contributor GOLD Sponsor

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    This is what I wrote regarding this, what is so absolute about it? No one here cares about what you are doing or how you are going about it; you asked for advice, and you received it. I acquiesce.
    "Forged pistons wouldn't be my first choice for the simple reason they are fit very loose and must be up to temperature before the engine is run under load; they have to expand to the bore. I would have gone with hypereutectic cast pistons (Mahle) which avoid the loose fit and are almost as robust as the forged."
     
  16. WetPleasure

    WetPleasure Member

    101
    Jan 30, 2021
    99 260 sundancer
    7.4 bravo3
    the motor is running fantastic and sounds amazing. Boat has yet to go to the water becauuse we are ironing out every last little issue. last one is a bad shift linkage in the bravo 3 which we replaced only to find out that the new lower shift cable has a wonky end to it, must have got a bad one that didn't pass quality control. Hope to have her on the water for a true test early next week.
     
    Nauti 97 and Nater Potater like this.

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