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 481988 Block
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Latech
Cochise

USA
366 Posts

Posted - 31 Dec 2010 :  6:05:18 PM  Show Profile  Reply with Quote
I was looking at the list on numbers for blocks and I noticed that in 71 +72 the 481988 was the number for the 350 block, in 73 + 74 the number was used for the 400.
Is there enough meat to bore the 350 to a 400 bore? Or is the number indicative of the casting only and the bore decided by the sleeve that is in it after casting?
Either way how far can you punch an early 350 ?

Chicagogoat
Cochise

USA
654 Posts

Posted - 31 Dec 2010 :  7:06:08 PM  Show Profile  Visit Chicagogoat's Homepage  Reply with Quote
From what I understand, although 350's and 326's share the same stroke/main journal size as a 400, their bore sizes are much smaller like +.200" smaller. Which is why they're almost always passed up for any serious build (400+ HP). The smaller bore size wont work well with larger valves that aftermarket heads or even hopped up stock heads have.

As to your ? on how much can a block be bored, .060 and anything more is usually not advisable not to mention the machine shop costs.

Pure Pontiac: learn it, live it, love it!
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Latech
Cochise

USA
366 Posts

Posted - 31 Dec 2010 :  7:59:32 PM  Show Profile  Reply with Quote
Yeah I figgered as much. I have a couple 350s . I am still gonna keep em around. One has #46 heads on it, the other has #94 heads and It is in the car now. Runs real good for a 350. The 389 I have is at the Mo Sheen shop as we speak.
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Chicagogoat
Cochise

USA
654 Posts

Posted - 31 Dec 2010 :  9:10:06 PM  Show Profile  Visit Chicagogoat's Homepage  Reply with Quote
You should keep 'em around just to keep a car runnin while you build up a better combo with that 389.

Pure Pontiac: learn it, live it, love it!
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WDCreech
Sitting Bull

USA
155 Posts

Posted - 01 Jan 2011 :  4:17:00 PM  Show Profile  Reply with Quote
quote:
Originally posted by Latech

I was looking at the list on numbers for blocks and I noticed that in 71 +72 the 481988 was the number for the 350 block, in 73 + 74 the number was used for the 400.
Is there enough meat to bore the 350 to a 400 bore? Or is the number indicative of the casting only and the bore decided by the sleeve that is in it after casting?
Either way how far can you punch an early 350 ?



I don't know what list you were looking at, but the lists that I have show the block casting 481988 as being "71, '72, '73, & "74 400 blocks. nowhere can I find it as a 350 block.


Bill
64 tube chassis GTO, 606 cu" IA tall deck, Superchief heads, glide, 2750lbs, 8.2550 @ 164.17, 1.1981-60'
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BearGFR
Bear

USA
569 Posts

Posted - 01 Jan 2011 :  4:30:26 PM  Show Profile  Visit BearGFR's Homepage  Reply with Quote
quote:
Originally posted by WDCreech

I don't know what list you were looking at, but the lists that I have show the block casting 481988 as being "71, '72, '73, & "74 400 blocks. nowhere can I find it as a 350 block.



Just wanted to add my encouragement to always double and triple check information that you find on web sites, people do sometimes make mistakes.

Bear
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Chicagogoat
Cochise

USA
654 Posts

Posted - 01 Jan 2011 :  5:10:32 PM  Show Profile  Visit Chicagogoat's Homepage  Reply with Quote
That's right that casting #481988 is a 400 block for sure, 481990 is a 350 block. That's good news for Latech.

Pure Pontiac: learn it, live it, love it!
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Latech
Cochise

USA
366 Posts

Posted - 01 Jan 2011 :  7:07:51 PM  Show Profile  Reply with Quote
Well it figures. Where i saw it, I cant find it now. I could have sworn that was what I was reading ,why else would I post a question like that. I read it somewhere and it did not make sense. I know that my 64 has a 71 350 in it as the number is 481990 on the block. the heads are #94s dated jan 71 .
But I saw the 481988 number and it was listed for 71-72 350 and 71-
74 400. I know I saw it, It did not make sense. I swear sometimes I am losing it.
My spare 350 (i am sure) i just checked it again(like 2 minutes ago)and it has a 481986 on it and #46 heads. I checked the date code when I picked it up at the yard and its a 73.
I wont say where I saw it ,it is a popular speed shop site,thats all I can say. I just checked and it is now correct,as to what I have been told here. But it has listed incorrect info in the past and still does in other areas, like head chamber volume for instance.
Kinda sucks to get the wrong info or different info on every place you go. Its enough to make you crazy.
Wallace has been about as accurate as any I have seen so far.
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Latech
Cochise

USA
366 Posts

Posted - 01 Jan 2011 :  7:10:35 PM  Show Profile  Reply with Quote
I wished all my blocks had 481988 on them. I dont have dumb luck like that.
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Nasty
Buffalo

63 Posts

Posted - 01 Jan 2011 :  7:54:58 PM  Show Profile  Reply with Quote
I may be wrong but most if not all the blocks I have seen have the CI size cast into them on the sideand lifter valley have 00 or 55 for 400 and 455... If I am wrong please forgive me.
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Latech
Cochise

USA
366 Posts

Posted - 01 Jan 2011 :  10:17:42 PM  Show Profile  Reply with Quote
No, I think they started doing that in the early 70s on 350 and 400 and in different places on the block. Some 428 had them a few years before. Nothing too consistent when it comes to labeling CI .I read up on it somewhere,but right now my mind is blank.
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mike mcarthur
Pony that Jumps

USA
2471 Posts

Posted - 01 Jan 2011 :  11:08:40 PM  Show Profile  Visit mike mcarthur's Homepage  Reply with Quote
I think the CI casting started in 70. My 69 block doesn't have it and the 70 block does. 70 is also when they started putting 5 motor mount holes in as well.

It's the stuff you learn after you know it all that's important
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duanemed1
Tribal Scout

USA
1 Posts

Posted - 28 Jan 2013 :  8:54:53 PM  Show Profile  Reply with Quote
I have a 1973 400 motor number 481988 dose any one know what kind of horse power this motor is putting out in a stock motor I am putting this motor in a 1956 pontiac
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Phil
The Great White Buffalo

USA
6416 Posts

Posted - 28 Jan 2013 :  9:33:33 PM  Show Profile  Reply with Quote
@175-185 hp stock.

"Chevy": even the name sounds cheap.
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cowboy
Buffalo

USA
79 Posts

Posted - 28 Jan 2013 :  9:43:41 PM  Show Profile  Reply with Quote
1973 400,s 170 to 230 what are the stamped letters on frount of the block

Edited by - cowboy on 28 Jan 2013 9:48:56 PM
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cortcomp
Coyote

USA
4368 Posts

Posted - 28 Jan 2013 :  9:54:36 PM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
honestly, the heads and cam will dictate the power, unless it's already been modified.
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cowboy
Buffalo

USA
79 Posts

Posted - 28 Jan 2013 :  10:21:28 PM  Show Profile  Reply with Quote
It,s my understanding the 2 letters or letter and number y1 indicate cam head and carb used in the assebly
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BearGFR
Bear

USA
569 Posts

Posted - 29 Jan 2013 :  11:09:40 AM  Show Profile  Visit BearGFR's Homepage  Reply with Quote
True - to fully identify what you've got you need several pieces of information:
Start with the 4 character date code on the top rear of the block near the distributor. Use this to ID the model year, it's important because Pontiac used the other engine codes to mean different things in different years.
Next, block casting number, rear of block "below" the passenger side head - 481988 in this case. Tells you engine family (400, 455, etc.) and sometimes a little more.
Now on to the 2 character engine code, front of block, passenger side, just below the head. This will tell you more, like what type of car was it in (GP, Tempest, etc.) transmission type (auto/manual), original carburetion, HP rating.
Next, cross-check all the above with the heads. They also have a 4 character date code on them and a "casting number" usually 2 raised characters cast into the tops of the center exhaust ports, but some heads do have 3 character codes in other places (like the "left end" exhaust ports in the case of 69 RA IV). You want to double check the heads because sometimes you'll run across "Frankenstein" engines that are wearing different heads than what they were born with, and that can affect HP.

I won't go into all the details of how to decode things because that information is readily available on the 'net. Google "Pontiac Engine Codes" and you'll find several sites.
Always check more than one site, sometimes folks make mistakes.

Bear

Edited by - BearGFR on 29 Jan 2013 11:11:53 AM
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