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  1. #1
    Join Date
    Oct 2004
    Newbury Park, CA

    Where Can I Find Info on Merc Engine Internals?

    As I look at used boats, we have the 454 Mag, 502 Mag, HP 500, and HP 525, but the information on what parts were actually used in building these engines is hard to find. For instance:

    Crank, Rods, Pistons - forged or cast?
    Intake Ports - retangular or oval?
    Exhaust Ports - rectangular or D-shaped?
    Piston pins - pressed or floating?
    Intake and Exhaust valve sizes?

    Chevy made a lot of versions of the big blocks, some a lot better than others for performance mods.



  2. #2
    Charter Member # 55 Charter Member Griff's Avatar
    My Boats:
    ..........32........... Active Thunder
    Join Date
    Oct 2000
    All the engines you listed have 4 bolt mains, forged cranks, forged pistons and forged rods. All GM parts.

    454mag, 502mag and HP500 all have GM rect port heads.
    454mag and 502mag have 2.19/1.88 valves
    HP500 has 2.25/.1.88 valves

    525efi uses Edlebrock aluminum heads. Not sure of valve sizes, probably 2.25/1.88's

    Piston Pins---I think are pressed in on all, but not sure.

  3. #3
    Platinum Member Platinum Member jeff32's Avatar
    My Boats:
    2000 triple 500 efi Sonic 45
    Join Date
    Jun 2004
    St-Hyacinthe, quebec, canada
    best kept secret!

  4. #4
    My Boats:
    2002 Eliminator Eagle XP, 1979 Cole TR-2
    Join Date
    Apr 2005
    Castro Valley, California
    I believe the HP500EFI has forged aftermarket rotating assemblies. Have been told Lunati crank, JE pistons, and Manley h-beam rods, along with the Crane roller cam and rocker components.


    62 Bel-Air 409

    260 Eagle XP HP500EFI

    2002 Corvette M6 Corvette

  5. #5
    My Boats:
    1996, Donzi, 22 Classic 502
    Join Date
    Jan 2002
    Further South East of Dome Island
    The big block Dennis Moore book has lots of this info in it.

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