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I have access to 2 blocks one is a 3970010 truck block and the other is a 3956618 which is an older 350 block. Both are 4 bolt mains. Is one casting better than the other as far as building a basic bracket motor?
 

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I have access to 2 blocks one is a 3970010 truck block and the other is a 3956618 which is an older 350 block. Both are 4 bolt mains. Is one casting better than the other as far as building a basic bracket motor?
If either were to happen to have 2482 main caps, use it.
 

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Not sure how true this is but I had heard the the blocks the says Hecho en Mexico are the best to use. As for what you have I'd use the 3970010is the one I'd use. Do you plan for any boost or nitrous etc?
 

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If neither have the nodular 2482 main caps, then have them both sonic checked and use the one with the best cylinder wall thickness/metal distribution.
 

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If neither have the nodular 2482 main caps, then have them both sonic checked and use the one with the best cylinder wall thickness/metal distribution.
What is the casting date on the 010 block? Stay away from anything 74 and older and DO NOT use a lightweight block. And follow the advice above.
 

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If neither have the nodular 2482 main caps, then have them both sonic checked and use the one with the best cylinder wall thickness/metal distribution.



X10000000000000000000000
 

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What is the casting date on the 010 block? Stay away from anything 74 and older and DO NOT use a lightweight block. And follow the advice above.

The cylinder walls are not compromised on the later blocks. I find that the early block have more issues with sonic testing/.
 

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The cylinder walls are not compromised on the later blocks. I find that the early block have more issues with sonic testing/.
I will pass along what I experienced I had with the lightweight block. The reason why I chose a lightweight block because I was going to fill it. Trying to keep the overall weight the same as older blocks. Two things, when the block was being bored & hone. The shop I was dealing with stated the block had a different noise when rough boring & honing. I didn't sound like the regular old style wide pad block. The block was soft, maid a lot of grinding dust and had small chips. I blew out black goo out of my nose for over a week. And I was wearing a dust-face mask. Lesson learned.
 

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I will pass along what I experienced I had with the lightweight block. The reason why I chose a lightweight block because I was going to fill it. Trying to keep the overall weight the same as older blocks. Two things, when the block was being bored & hone. The shop I was dealing with stated the block had a different noise when rough boring & honing. I didn't sound like the regular old style wide pad block. The block was soft, maid a lot of grinding dust and had small chips. I blew out black goo out of my nose for over a week. And I was wearing a dust-face mask. Lesson learned.
Do me one favor. Don’t fill it.
 

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This.
You can visibly see an off-center cam bore.



Can't go by that as there is a front plate installed during the casing it can be off, I was told this many years ago by a guy who worked for GM. and sonic testing proves him right.

I have blocks that show zero core shift that are junk and I have seen block that show a lot of core shift and they are fine.

Instead of guessing sonic test is that final word.
 

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I will pass along what I experienced I had with the lightweight block. The reason why I chose a lightweight block because I was going to fill it. Trying to keep the overall weight the same as older blocks. Two things, when the block was being bored & hone. The shop I was dealing with stated the block had a different noise when rough boring & honing. I didn't sound like the regular old style wide pad block. The block was soft, maid a lot of grinding dust and had small chips. I blew out black goo out of my nose for over a week. And I was wearing a dust-face mask. Lesson learned.

If it was that soft you would be striping out the head bolt holes.
 

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Can't go by that as there is a front plate installed during the casing it can be off, I was told this many years ago by a guy who worked for GM. and sonic testing proves him right.

I have blocks that show zero core shift that are junk and I have seen block that show a lot of core shift and they are fine.

Instead of guessing sonic test is that final word.
Right on, Carl.

Same is true for the so called "010" and "020" casting numbers in the timing cover area or back of the block denoting "high nickel"...it's a oft repeated myth, Chevy never cast any stock production "high nickel" blocks....those numbers simply denote what core box and core box end plates are in that mold...they have nothing to do with metallurgical content.
That info came direct from a former Flint Engine Plant employee.
 

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Right on, Carl.

Same is true for the so called "010" and "020" casting numbers in the timing cover area or back of the block denoting "high nickel"...it's a oft repeated myth, Chevy never cast any stock production "high nickel" blocks....those numbers simply denote what core box and core box end plates are in that mold...they have nothing to do with metallurgical content.
That info came direct from a former Flint Engine Plant employee.
Brian Berry?
 

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Right on, Carl.

Same is true for the so called "010" and "020" casting numbers in the timing cover area or back of the block denoting "high nickel"...it's a oft repeated myth, Chevy never cast any stock production "high nickel" blocks....those numbers simply denote what core box and core box end plates are in that mold...they have nothing to do with metallurgical content.
That info came direct from a former Flint Engine Plant employee.



When I do a sonic test I also look at the sonic velocity which gives me a good idea of the quality of the casting material.
 
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