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  1. #1
    Join Date
    Sep 2017
    Location
    New Bern, NC
    Posts
    3

    Default Rebuilding Mark IV's 454 cid with one counter rotating

    Hi to all; newly registered to site, following for awhile;

    I am thinking about rebuilding two 454 bare blocks, one to be counter rotating. (Then, when necessary swapping for the original iron in my boat.)

    My research has shown that the two engines are identical except for timing drive, seals, camshaft and of course firing order. What puzzles me is that one site lists a different crusader BLOCK part number. Since the cranks are the same, is their some oiling issue from rotating the crankshaft in the opposite direction. Does the crankshaft have to be drilled differently in the counter rotating engine? Since I am not tearing down the original beasts, I can't know this in advance of the rebuilds.

    Thanks to all for all the great information on this site, and any help appreciated.

    Cheers,

    Larry

    P.S. anyone with bare blocks suitable for rebuild, I am interested...

  2. #2
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Rebuilding Mark IV's 454 cid with one counter rotating

    Welcome Aboard!!

    I've done a few and never found any differences in the bare blocks. The rear main seals with the 'nubs' are oriented 'backwards' on the RH engines. The front seals nowadays are 'universal' and not rotation sensitive. The pistons also go in 'backwards on the RH engine. The standard build uses a four bolt main block.

    I'd suggest finding a factory service manual as it will spell out the differences if you are doing it. The other option would be to let the machinist assemble the block - just make sure they understand your application is marine.

  3. #3
    Join Date
    Sep 2017
    Location
    New Bern, NC
    Posts
    3

    Default Re: Rebuilding Mark IV's 454 cid with one counter rotating

    Thanks, will try to find one. On the counter rotators you built, did you have any special machine work done to the crankshaft? I was also thinking about changing over to roller tappets understanding there may be some power advantage by reducing engine power wasted on the flat tappets. Or would you recommend sticking with the flat tappets? Regards, Larry

  4. #4
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Rebuilding Mark IV's 454 cid with one counter rotating

    nothing special to the RH crank....did have the last pair balanced....

    on the same pair, we used roller rockers with the standard flat tappet camshafts....roller lifters will help reduce the friction but don't come cheap.....I can't say if they would be cost effective or not....if you plan to really use the boat (300+ hours a year) then your payback opportunity comes quicker....

    which ever you pick, I would suggest maintaining the 'peanut port' heads (they came be tapered to the gaskets but don't open them up to true oval port size) and maintaining a standard production cam envelope; don't exceed max lift/duration of the factory (GM) cams....

  5. #5
    Join Date
    Aug 2008
    Location
    Fairport, NY
    Posts
    1,624

    Default Re: Rebuilding Mark IV's 454 cid with one counter rotating

    Add the starter too! I had felpro special rear main seal for RH engine but can't tell you what the diff was.

  6. #6
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,758

    Default Re: Rebuilding Mark IV's 454 cid with one counter rotating

    i finally got access to my shop manuals.....turns out they use 'helical grooves' where I used 'nubs' to describe the rear seal....and that style can be found on the front or rear seal. They also have service seals that are smooth and can be used in either RH or LH applications.....

  7. #7
    Join Date
    Sep 2017
    Location
    New Bern, NC
    Posts
    3

    Default Re: Rebuilding Mark IV's 454 cid with one counter rotating

    Yes, found a service manual; shows the rear seal has like little veins that must form like a pressure head towards the seal lip, makes sense to have them opposite for opposite rotation, sorta like props, eh?

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