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Thread: checking casting numbers? looking for a block.

  1. #1
    Senior Member
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    Apr 2010
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    Im in the process of looking for a tall deck BBC and im trying to find something with thick cylinder walls, should i be checking out casting numbers? i found some websites that show the dates and some say heavy duty what should i look for? thanks, chris.

  2. #2
    Clown
    I run A #14044807 Block 4.500 Bore.10.200Deck
    Motor has held up to alot of shit.
    But I'm not seartin about the wall thickness. If I remeber corectley My block Is a Siemiesed Bore ,But don't hold me to that I have alot of Motor Projects In the works and can't remeber every fine detail.
    I do know Friends have gone to 4.600 safely.
    What are you looking to but together????

  3. #3
    Senior Member
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    you have a 4 bolt bowtie mk 4 cnc prep tall deck, they come in either 4.250 or 4.495 bores. thats a nice block.I had a .070 over 4.250 tall deck sonic checked , its way too thin.

  4. #4
    Fiat48
    First there was the old 427 tall deck (probably what you have) that was supposed to be a little thicker wall casting than most of the old low decks. But there is always the chance for core shift (probably what problem you have now).
    The newer "Green Marine" 14044808 (me knowing that shows my age!) or Bowtie block is totaly different and definately a heavy wall casting. Merlin, Maskin blocks and the like all have the same heavy walls (solid between the cylinders) and most go 4.500 with ease and 4.625 to be about max bore size.
    I would suggest that if you are paying all the labor to have machine work done, that you start out with a bowtie, Merlin or Maskin block and leave the old 427 tall decks alone. I am partial to the Maskin but throw no stones at any of the new blocks.
    There is a thin wall casting that GM made (they deny this) as a replacement 427 tall deck when cores were needed. I have only seen a few and the dead giveaway is a 7.5L cast into the side of the block, plus it is a very nice looking casting (new casting) versus the old rough cast 427 tall deck. GM no longer casts this old block.

  5. #5
    DogHouse
    I have a tall deck Mk IV bowtie block that is in fair but serviceable condition, currently at 4.560" bores. PM or email if interested, price will be very reasonable.
    -brian

  6. #6
    Senior Member
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    i saw one of those clean cast newer tall decks today at the long beach hot rod swapmeet, it actually had 7.0 on the side of it, not 7.5 are they the same?

  7. #7
    Senior Member
    Join Date
    Apr 2010
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    6,425
    i saw one of those clean cast newer tall decks today at the long beach hot rod swapmeet, it actually had 7.0 on the side of it, not 7.5 are they the same? doghouse, thanks for the reply, not really looking for anything in less than good shape.

  8. #8
    Fiat48
    The 4 tall decks that are here in the shop don't have 7.0L or 7.5L cast into the side. I could be wrong about the number...may have been 7.0 but I remember the L for sure. Clean casting. Probably was one of them. Now this is just a guess..but the I thought the L was for Litre, which we didn't do in the 60's & 70's.

  9. #9
    Liberator TJ1984
    I have a "Newer " GM Mercury Marine 4 bolt block.
    It has the 7.4L " liter " stamp on the sides = stock bore 454 but I dont know the wall thickness or how much it will bore to...

  10. #10
    DogHouse
    Fiat48, the "Maskin" block, is that the Dart block or something different? Just curious as I had not heard that before.
    thanks,
    -brian

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