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Siamese bore 5.3 block worth it?

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Old Apr 21, 2017 | 11:28 AM
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Default Siamese bore 5.3 block worth it?

I currently have an L33 that threw a rod and cracked the block in the rear, so I am in search of a new block.

Would it be worthwhile to try and go for a siamese bore block? The L33 has a 24x reluctor wheel, and the siamese bore blocks usually have a 58x reluctor wheel from what I have seen.

If I were to get the siamese bore block with the 58x reluctor wheel, could I simply swap over the 24x crank from my L33? OR could another option be simply just swapping out for the correct ECU or is the wiring harness completely different between the 24x and 58x as well?
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Old Apr 21, 2017 | 11:31 AM
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What are you trying to do with it?
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Old Apr 21, 2017 | 11:54 AM
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Forgot to put that in there. Going to be turbocharging it, starting out at around 600-700rwhp, but who knows how much I'll end up trying to make once the bug bites.
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Old Apr 21, 2017 | 12:28 PM
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The 58X blocks have the cam sensor in the front cover, so you'd have to do a 1X cam sprocket instead of the 4X singlebolt sprocket that comes in those motors. You'd also need to extend the cam sensor wiring.
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Old Apr 21, 2017 | 12:41 PM
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Originally Posted by shainiac
The 58X blocks have the cam sensor in the front cover, so you'd have to do a 1X cam sprocket instead of the 4X singlebolt sprocket that comes in those motors. You'd also need to extend the cam sensor wiring.
Yea, I remember that fact as well, which would be a easy enough since I'll be swapping to a turbo cam anyways. The more difficult issue is getting around the 58x/24x reluctor wheel and what the best option is or if it's even that big of an upgrade.

Seems like the siamese bore is primarily better for those who are looking to bore their cylinder walls out more, and seems like more people would have some sort of failure with the rods before cracking a non-siamese bore block even.
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Old Apr 21, 2017 | 12:45 PM
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For 700whp I wouldn't worry about it. Also not all gen 4 blocks have the 58X reluctor. I split open a 06' LH6 last weekend with a 24X. Regardless though you can always swap reluctor wheels.
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Old Apr 21, 2017 | 01:43 PM
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Which blocks are siamese? I thought just the LS7.
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Old Apr 21, 2017 | 06:29 PM
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Stock internals but worried about block... Hmmmm
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Old Apr 22, 2017 | 11:26 AM
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Originally Posted by oscs
For 700whp I wouldn't worry about it. Also not all gen 4 blocks have the 58X reluctor. I split open a 06' LH6 last weekend with a 24X. Regardless though you can always swap reluctor wheels.
That's what I am leaning towards, that it might not really matter. I really haven't too many blocks crack before other components failed anyways.

Originally Posted by tblentrprz
Which blocks are siamese? I thought just the LS7.
There's a few out there, I think the LS2 also uses it, etc. I think they started using Siamese blocks after a certain year, but I don't remember off the top of my head right now.
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Old Apr 23, 2017 | 05:54 PM
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The factory gen 3 blocks are fine to 1000whp. Gen 4 even more so. The Gen 4 aluminum blocks are pretty damn strong. They don't have core shift issues like the LS2/3 blocks. But again, for 700whp really any LS block will work.
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