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Discussion Starter · #1 ·
The old dude next door used to be an amc freak, he has been cleaning out all kinds of parts and such and let me grab pretty much whatever I wanted. I want to change my yj engine someday so I grabbed a 401 block. The problem is that the bore is 3.75" but from what I've read it should be 4.165". The block clearly says 401 in 2 different spots. The only other mark is what looks like an x or a + maybe. Is the 401 a casting reference and this is something smaller? If so, what?:confused:
 

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It's a Service Replacement block. A modified GEN-3 design, it has a 401 casting and with a 360 bore and thicker deck. I could be buil as a 343-401 GEN-2 or GEN-3 engine. First apperd in 70 IIRC.

BTW very nice find. Spro will probally have a hard on for it since. It's considered to be a heavty duty race engine.
 

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Discussion Starter · #5 ·
Its an AMC engine, worth more as scrap then anything. :thumb:

For how heavy that block is, I bet it will bring you 30 bucks.
He called a guy that he used to wrench with and he's gonna take a look at it. The guy said he has a 401 block I can have if this 1 is junk.
 

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Discussion Starter · #6 ·
Sell it to PP for 1 million dollars :thumb:
I don't think he'd want it. The guy came over and looked at it, it's not a 401. He wasn't sure why it was missmarked but he had a 401 block that he was gonna scrap and he swapped me.:woot:
 

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I am the law.
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I don't think he'd want it. The guy came over and looked at it, it's not a 401. He wasn't sure why it was missmarked but he had a 401 block that he was gonna scrap and he swapped me.:woot:
I think you should have listened to Rocky. Why you didn't call me when this first came up, I have no idea. I have a bad feeling about it, but I'm going to look through my AMC-List archive.
 

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I am the law.
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Didn't you post a big old thread about this 401x block that was super rare? Used 401 crank and 304 bore. :miff:

Edit: http://www.greatlakes4x4.com/showthread.php?t=30363&highlight=401x+amc

Yes, but he said he found "401" in two places. AMC blocks have the engine size cast in two places - under each engine mount. That 401X block had it in the valley pan, which he said nothing about and 3.75 is the 304 bore. That's why it sounded more like a service replacement scenario to me.
 

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Yes, but he said he found "401" in two places. AMC blocks have the engine size cast in two places - under each engine mount. That 401X block had it in the valley pan, which he said nothing about and 3.75 is the 304 bore. That's why it sounded more like a service replacement scenario to me.
So next time he should do more research :tonka:
 

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Discussion Starter · #12 ·
I thought I did pretty good since that was the first and only time I ever even heard of the damn thing.:sonicjay:
 
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