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Discussion Starter #1
After hot tanking a block there is "Marine" cast into the block above the bellhousing flange. A casting # search turns up just a basic decription, not mentioning marine at all. Anyone have any insight what it indicates. I always thought the blocks where cast for automotive, and distrubited from there for application.
Suprised to see Marine on it.
Be safe, schick
 

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After hot tanking a block there is "Marine" cast into the block above the bellhousing flange. A casting # search turns up just a basic decription, not mentioning marine at all. Anyone have any insight what it indicates. I always thought the blocks where cast for automotive, and distrubited from there for application.
Suprised to see Marine on it.
Be safe, schick
Was this a Packard or Studebaker?



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Just Me
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Most if not all of the manufacturers had marine divisions at one point. I know several cast blocks as marine for sure. What type block do you have?

I'm betting either Chevy or Chrysler.
 

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Was this a Packard or Studebaker?
The Packard 4M-2500 was a dedicated marine engine. A high performance supercharged V-12 requiring 100 octane av gas and producing 1500HP. Three of these engines powered each of the 800 PT boats built by the US during WWII.
 

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steelcomp was here
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The Packard 4M-2500 was a dedicated marine engine. A high performance supercharged V-12 requiring 100 octane av gas and producing 1500HP. Three of these engines powered each of the 800 PT boats built by the US during WWII.
Very cool old engines. :))THumbsUp

300px-Packard_3A-2500_USAF.jpg
 

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Discussion Starter #7
This one is a chevy. Casting #364776.
All l see in listings is "1968-1985 427 tall deck 4 bolt"
Which it is 4.250 bore with a 6223 3.76 in it (l assume, did not measure before teardown). 4 ring pistons
Any thoughts?
 

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This one is a chevy. Casting #364776.
All l see in listings is "1968-1985 427 tall deck 4 bolt"
Which it is 4.250 bore with a 6223 3.76 in it (l assume, did not measure before teardown). 4 ring pistons
Any thoughts?
Sounds like a truck block to me.
 

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Some guy
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This one is a chevy. Casting #364776.
All l see in listings is "1968-1985 427 tall deck 4 bolt"
Which it is 4.250 bore with a 6223 3.76 in it (l assume, did not measure before teardown). 4 ring pistons
Any thoughts?
There were some "marine" tall deck blocks made that were supposedly extra thick wall and would go to a real large bore size. Several years ago (6-8?)there were still a bunch of them around for sale new.
 

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Discussion Starter #10
Truck block is what l thought. Just supprised to see the marine designation after hot tank. You guys have seen lots more blocks than l. Just thought l would ask,
Thanks for the input!!!!
 

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Lot of truck blocks have "marine" cast into them. Most of them in the T chain area. Some just have "truck"
Of the 4 truck blocks I have, 2 have marine, 2 don't.
Same 4 ring assembly was used for trucks, low performance marine, and industrial engines.

Then there is the so called special marine that Obnoxious is talking about, that is a precursor to the bow tie. Virtually identical to the standard MKIV block, but like he said, they will take 4.5 bore. They are most easily spotted because no early dated 427 tall deck can swallow a 4.25 crank without grinding, and the special marine tall deck can easily.

Much later service truck/marine blocks can handle a 4.25 stroke without grinding. You can spot those blocks by the rear oil gallery bosses and the rear cam plug boss being machined flat, not raw rounded as cast like a normal MKIV block. Using normal hex headed oil restrictors in those blocks will result in the restrictor hitting the flex plate/flywheel. You have to use Gen 5-6 "allen" type restrictors that set flush.
THESE BLOCKS ARE THE BIGGEST PILE OF SHIT GM EVER CAST!!!!
Thin cylinder walls, thin decks. Nothing like an early truck block. I wouldn't give you 250.00 for a brand new one.



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Discussion Starter #13
Is the crank for sale ?
Sorry wiz, l sent it to the swapmeet yesterday, and sold last night before the meet opened this morning. Was a good crank std/std, had it in the spam section for about a month.
 

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There were some "marine" tall deck blocks made that were supposedly extra thick wall and would go to a real large bore size. Several years ago (6-8?)there were still a bunch of them around for sale new.
I was working with a guy who had two Eickert tall deck 496's that had "marine" on the blocks. Had one sonic checked and there was nothing less than .300" on cyl walls. I believe this was as bob said, the predecessor to the Bowtie block.
 

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Discussion Starter #15
All good infornation guys, thanks for the help. Sounds like someone will get a great block. This one is in the parts spam too, for 450.00. Magged/ and hot tanked. Needs about .030 bore.
Thanks again, be safe. schick
 

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I was working with a guy who had two Eickert tall deck 496's that had "marine" on the blocks. Had one sonic checked and there was nothing less than .300" on cyl walls. I believe this was as bob said, the predecessor to the Bowtie block.
My understanding is, Merc Racing got GM to cast up some heavy wall blocks that they stroked to 496. Why they felt they needed the blocks to be thicker is anybody's guess. Some of them did however get bored to 4.44 and 4" cranks and made 496 as well, but they didn't need a tall deck to that.
never heard of any getting both the 4.25 crank and a 4.44 bore, but I am sure it was done, just not raced.
There are some rather rare pieces out there floating around , like GM, Winter's cast dual plane L88/LS6 type manifolds with cast in brass inserts in the front cross over that fit a tall deck, and longer cap screw "K" rods to fit the blocks with either cranks.
I have one of the tall deck marine blocks, and its a stout piece. But it lacks things like blind head bolt holes that the later Mark IV Bow Ties had.



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