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mo balls than $cents$
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Discussion Starter #1
guys, are the 400 blocks pretty weak? only thing i can remember about them is the cooling issue, but that's a non issue in a jetboat. what were the other downsides? i've got a nice block, just didn't know if its worth using of if i'm gonna have to make this a 2yr project, buy a lil m block:)sphss
 

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I'd think the lack of head gasket surface(siameesed cyl walls) would make head gaskets a challenge with a boosted appl.
 

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Cantard
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5,017 Posts
guys, are the 400 blocks pretty weak? only thing i can remember about them is the cooling issue, but that's a non issue in a jetboat. what were the other downsides? i've got a nice block, just didn't know if its worth using of if i'm gonna have to make this a 2yr project, buy a lil m block:)sphss
You put those heads on it that I sent you the link to and you will need a dust pan to pick it up. lol
 

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I'd think the lack of head gasket surface(siameesed cyl walls) would make head gaskets a challenge with a boosted appl.
one would think that this would be one of the big problems, but evidently it isn't because the rocket and dart blocks are used for high boost, big spray, and big compression, and they have the same bore spacing. it's all in the head gasket you use, and the fact that the block doesn't move around as much.



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Some guy
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guys, are the 400 blocks pretty weak? only thing i can remember about them is the cooling issue, but that's a non issue in a jetboat. what were the other downsides? i've got a nice block, just didn't know if its worth using of if i'm gonna have to make this a 2yr project, buy a lil m block:)sphss
I don't see where you mention forced induction here, maybe I missed something.

We run 400 blocks in a dirt modified that I build engines for. We had a destroked combination that we were running in a 4 bolt block on race gas, no issues except the bore was a little tired and we went to a 2 bolt block for this year.
 

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mo balls than $cents$
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11,734 Posts
Discussion Starter #9
i've got a 2 bolt, thought i could 4 bolt it with splayed billet caps, maybe get 1000hp outta it with some boost. what is making them split at 700hp?
 

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mo balls than $cents$
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Discussion Starter #11
Broken mains. Should be able to buy a block for about $1900
found a boat to put it in, he's sending me pics tonite:)devil lil 17ft predator, so i'll be buyin the lil m block for this project. this will be my 1st 2yr project, so next summer will be spent on the toon:)sphss
 

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mo balls than $cents$
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11,734 Posts
Discussion Starter #13
thanx for the info guys, looks like i just need to freshen up the 412sbc and put it to the side for a spare;) i'll buy a lil m block.
 

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Motown

Motown Cast Iron Blocks
At first glance, one of the more noticeable differences between the World Motown and OEM Chevrolet blocks are the “bulges” at each cylinder. That’s because the “Motown” has thicker cylinder walls, and the water jackets have been expanded to provide required cooling. The Motown block can be bored to max of 4.200". DO NOT EXCEED.
 

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Cantard
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found a boat to put it in, he's sending me pics tonite:)devil lil 17ft predator, so i'll be buyin the lil m block for this project. this will be my 1st 2yr project, so next summer will be spent on the toon:)sphss
2 year projects are much better than half done half right 1 year projects.
 

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The "509" or "817" casting numbers were the most desirable. The 511 pieces (usually 4 bolt) were extremely weak. Treat them like the plague. If converted to splayed caps, and a rear strap at the least, they will live reasonably well at the 750 hp range in a stock car. (509 and 817 blocks) You should expect about the same.
Plug the steam holes. Over 3000 rpm's they don't do much.
They were prone to cracking in the lifter valley area.
Back in the day..before dart blocks, it was the only alternative to a bowtie block.
A set of GOOD (Pro Gram, or like) billet caps will cost over 400 (including front cap and strap). Add machine work, factor in it is still a stock block, and it is no longer a deal.
Now, don't forget your dart block or world piece will also need work. Mains might be right, needs to be decked, honed, etc. So the 1900 ish is not 1900- ready to start bolting together.
Just food for though.
Wags
 

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Cantard
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Could it be braced with say a main stud girdle? if there is such a thing for sbc's
Problem is that if you do the splayed caps and even if you fill them with hard block the next step is they break in the lifter valley usualy down the driver side.
I know you would like to use it but I just dont have any good answers for you.
 
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