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Thread: gen4 bbc blocks

  1. #1
    Senior Member
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    when did chevy change to the gen 5 block? thanks
    pat(slotracer) :crossx:

  2. #2
    cyclone
    I think when the Vortec engines came out. 1995 maybe?

  3. #3
    Senior Member
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    then a 89 should be a gen4 block.
    pat(slotracer) :220v:

  4. #4
    Senior Member
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    Technically, it's "Mark IV", "Gen V" and "Gen VI".
    Gen V production started in 1991.
    I think Gen VI started in 1996.
    Pat with all the BBC that have passed through your garage you should have this stuff memorized by now. Play it safe and always get a block casting number and check it at www.Mortec.com

  5. #5
    Senior Member
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    craig just never played with any bbc that new. never thought to get the block number. thanks
    pat(slotracer)

  6. #6
    SmokinLowriderSS
    Some stuff from:http://chevyhiperformance.com/techar...67/index1.html
    The Mark III never saw the light of day, but the Mark IV caused a sensation when it was unveiled in the 1965 Corvette. The Mark IV’s expansive rocker covers concealed a new “semi-hemi” valve layout that promised to take engine airflow to new heights. Other Rat-motor variants soon followed, with displacements ranging from 366ci truck engines to 510ci Can Am specials. Then in 1991, the GEN V arrived, and the big-block world shifted on its axis. Why the change in nomenclature from Mark IV to GEN V? The General’s cross-town rivals in Dearborn, Michigan, had already hung the Mark V moniker on its line of Lincoln luxury barges, and GM’s lawyers weren’t spoiling for a fight. So, along with all the changes in hardware, the big-block got a new name.
    The GEN VI arrived on the scene in 1996 wearing a fashionable new Vortec nameplate. Compared to the sweeping changes that had taken place five years earlier, the GEN VI revisions were relatively minor. The introduction of hydraulic-roller camshafts drove changes in the lifter-boss machining and timing set. The GEN VI also addressed service issues, by including the block-mounted fuel pump and the clutch pivot-ball mount on GEN V versions

  7. #7
    steelcomp
    The Mark IV’s expansive rocker covers concealed a new “semi-hemi” valve layout LOL!! Gotta love advertising!

  8. #8
    Senior Member
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    The Mark III never saw the light of day, but the Mark IV caused a sensation when it was unveiled in the 1965 Corvette.
    Hey Smoke...
    what about the '63 chevy 427ci Biscane's (used mainly in drag racing)?...where they Mark III or Mark IV engines?...also...i think the '64 chevy NASCAR race cars used 427's?
    fastrat

  9. #9
    Floored
    those 427's were a 409 called the Z11.http://www.geocities.com/greatameric...-63impala.html

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