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Joined: Aug 2005
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I'm getting conflicting information from the casting numbers listings linked off of the inliners site. The main casting numbers list on the site lists the the block number 3837012 as being a 1955-57 261 block. One of the other sites lists it as being a 55-59 261 application...cross generational? i thought 58 was the cutoff for the second and third gen? yet another site lists this same block number being a 1942-1951 chevy car 216! Which is correct?
Anyone have a master parts book they can confirm any one of these to be true?

Thanks!


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Dear Josh;

They probably just made a few more than expeced in that factory. You can tell by the oil holes,

You can see if It's 216 by checking the sideplate holes.


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There should also be a date casting number on the block, I think it's behind the starter on the passenger side. This should help you better identify that block. Also you can spot a 261 by the two "captains bars" cast into the block on both sides. Right above the starter on the right side and in the upper middle on the left side. For what it's worth, my casting number list shows it to be a 55-57 261.


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Well, the reason I'm asking is because I'm in talks with a guy about buying his block. Unfortunately he's on opposite sides of the country from me. He said his block is a 56 261 with the above mentioned casting number. However, he claims that it's a full flow block, and is also in unaltered stock condition. That's why i'm confused. An unaltered 56 block should NOT be full flow, according to everything I've been told. He has no digital camera, so he can't just e-mail me pics. He said he'd snail mail'em to me though. Maybe he's not fully aware of what I meant by full flow. Maybe he thought I meant "full pressure" as in the second generation 235's. I don't know. I guess I'll have to wait and see what his pictures look like.

Thanks.

Josh


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J;

It could be one if the pin has been moved or had an oil filter from the factory.

Filters were optional or a 'special order' way back when.


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There would be no pin to move if it isn't a 59-62 261 as there would be nothing to switch, since they were by-pass only (54-58).

the 54-58 261's are not full flow. It is possible that it has been modified to be full flow, or more likely as you say, he isn't fully understanding of what you're talking about. There are alot of people out there and on this site that will interchange "full flow" and "full pressure" without thinking...

If it's a full flow version, it's gonna have the 1/2" NPT holes for the oil filter lines, not the little 1/8" NPT ones like the by-pass versions.

Get the date code from above the starter and the stamped serial number (on the pad right behind the dizzy). That should tell you for sure what it is.


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Thanks guys. I'll wait to see the pictures he sends. He says it's date coded a 56. If that is the case, and it's full flow then bottom line, it's been modified. Hopefully it's just a miscommunication, and it is in fact an unmolested block. He has an 848 head I'm going to snag as well, so I hope the deal goes well. I guess even if the block isn't what i'm looking for, I can still get the head. I think he's selling them seperately.


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56 GMC 101 Deluxe NAPCO 4x4 (270)

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