455 casting #'s

[david68caligs]

I read in "How To Build Max-Performance Buick Engines" book that 76 and service replacement blocks are the sturdiest and suffer less from core shift. I have located a block that is supposed to be from a 76 Buick with casting # 1241735. According to the Buick Big Block Casting #'s provided on this site, the above mentioned casting # is 72-75. There is another sequentially higher numbered casting # (1242694) with unknown designation. Logic would suggest the numerically higher # would be a later production, possibly 76 or service replacement casting. Although some research lead me to Gesslers Head Porting who has some new old stock items, including a 1242694 block labeled 1971 replacement block.

This is the link, its at the bottom of the page. http://www.gesslerheadporting.com/ge...6!OpenDocument


Anybody have any additional knowledge/input?

[Bob]

I think the site numbers do identify 1241735 as a 70-76 block the same for 1242694...

http://www.teambuick.com/forums/view...bers_big_block

According to Automotive Rebuilders Assosciation reference either number can be from a 70 -76

[david68caligs]

Thanks, after further searching I found the same. Some sites show the casting # to 76, some don't. Since 75,76 blocks are considered to be heavier cast and less prone to core shift. Now my Question is, If CASTING # 1241735 is produced from 72-75, how do I tell if its the later heavier casting? Short of weighing it. Guess I could take a scale to the sellers garage.

[Buford26]

The engine production code and serial number should tell you the year. Here is where to find the numbers on the block:

http://www.teambuick.com/forums/view...t_engine_where

I'm not sure if the above pictures are totally correct, because I think the engine serial number on a '76 might be stamped on the passenger side cyclinder bank just below the cyclinder head and behind the water pump, so check there if you can't find it as shown in the picture. Here is a list of production codes:

http://www.teambuick.com/forums/view...t_engine_76-82

http://www.teambuick.com/forums/view...t_engine_63-75

The engine serial number should be 8 or 9 digits and would match the last 8 of the VIN from the car it was from. Here is an example of a 9 digit serial number (the 8 digit serial number would omit the division code at the beginning).

41H100001

4 = GM division digit = Buick
1 = last digit of production year = 1971 (1975 = 5, 1976 = 6)
H = production plant digit = Flint, MI
100001 = last six digits are sequential production number unique to car/engine