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Dart Big M Block Questions

Old 01-03-2022, 10:03 AM
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Ladies, Gentlemen and others....

Quick question, that may lead to others....

I'm entertaining a fantasy of building a 632 monster, starting from a Dart Big M block. Can this engine be built and shoehorned into the same space as the 496HO that's currently under the sundeck of my PowerQuest 280 Silencer, and keep it under the hood? Looking for any contingencies/concessions that would be involved in making it work, not so much reasons why it won't. Obviously, if it just can't, it just can't, but I figure since I'm starting from scratch......

Thought I'd get this question outta the way first, then we can move onto more in-depth material.

Thanks. Brad.
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Old 01-03-2022, 10:24 AM
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You made me laugh with the “and others”. So sad but true. Just hope it hasn’t hit the offshore world quite yet anyway!!! 😂.

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Old 01-03-2022, 10:53 AM
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Originally Posted by getrdunn View Post
You made me laugh with the “and others”. So sad but true. Just hope it hasn’t hit the offshore world quite yet anyway!!! 😂.
Geterdunn,

Strangely enough, I got it from a HS biology teacher during my sophomore year, something like ‘86. She was a hoot.

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Old 01-03-2022, 11:06 AM
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Originally Posted by Brad Christy View Post
Geterdunn,

Strangely enough, I got it from a HS biology teacher during my sophomore year, something like ‘86. She was a hoot.

Thanks. Brad.
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She probably read 1984 also. I was just a few years ahead of you graduating in 85 but wasn’t paying Attention to anything. She was obviously in the know how!
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Old 01-03-2022, 11:50 AM
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Originally Posted by Brad Christy View Post
Ladies, Gentlemen and others....

Quick question, that may lead to others....

I'm entertaining a fantasy of building a 632 monster, starting from a Dart Big M block. Can this engine be built and shoehorned into the same space as the 496HO that's currently under the sundeck of my PowerQuest 280 Silencer, and keep it under the hood? Looking for any contingencies/concessions that would be involved in making it work, not so much reasons why it won't. Obviously, if it just can't, it just can't, but I figure since I'm starting from scratch......

Thought I'd get this question outta the way first, then we can move onto more in-depth material.

Thanks. Brad.
(937)-545-8991
All depends on your intake and exhaust systems. But the 496 has a 10.2” deck height like the 632 would, so theoretically it’s possible.
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Old 01-03-2022, 12:01 PM
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Originally Posted by hogie roll View Post
All depends on your intake and exhaust systems. But the 496 has a 10.2” deck height like the 632 would, so theoretically it’s possible.
Hogie,

What about block length? I just trying to imagine cramming four cylinders per bank at 4.6”+ diameter into a block the same length as one with a bore of 4.3”. Something’s gotta give. I don’t know how much extra length in the block I can accommodate. Just curious where the extra space is taken up. Cylinder wall? Block length? I’m new to this, as is obvious.

Thanks. Brad.
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Old 01-03-2022, 12:33 PM
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block stays the same it the bore size that changes, even a sbc and a bbc are the same length from the motor mount back
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Old 01-03-2022, 01:10 PM
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Originally Posted by Brad Christy View Post
Hogie,

What about block length? I just trying to imagine cramming four cylinders per bank at 4.6”+ diameter into a block the same length as one with a bore of 4.3”. Something’s gotta give. I don’t know how much extra length in the block I can accommodate. Just curious where the extra space is taken up. Cylinder wall? Block length? I’m new to this, as is obvious.

Thanks. Brad.
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Mark IV 454's and your latest Gen 496 are 4.250" bore standard.
The ability to go the 4.625" max bore most aftermarket blocks suggest is the fact the Mark IV big block was designed with 4.840" bore centers and carried onto the later generations.
So, couple that with the thicker and "siamesed" cylinders on the aftermarket blocks are cast with, they can go the 4.625" and there's no need for the block to be longer.
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Old 01-03-2022, 01:11 PM
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Old 01-03-2022, 01:29 PM
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Originally Posted by cheech View Post
Mark IV 454's and your latest Gen 496 are 4.250" bore standard.
The ability to go the 4.625" max bore most aftermarket blocks suggest is the fact the Mark IV big block was designed with 4.840" bore centers and carried onto the later generations.
So, couple that with the thicker and "siamesed" cylinders on the aftermarket blocks are cast with, they can go the 4.625" and there's no need for the block to be longer.
Cheech,

Thanks for the info.

Just to be clear, speaking specifically to length, I can expect a fully dressed Dart Big M engine to fit in the same space as the Merc 496 I have now….? Technically, it should be shorter, given there is a ProCharger pulley that would not be in the mix. Or this space could be repurposed for a dry sump oil pump pulley. Is this correct?
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