Need part number for 4 bolt LT1 or LT4 block
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Joined: Dec 2003
Posts: 1,526
From: Madison, Wi
Re: Need part number for 4 bolt LT1 or LT4 block
LT1 and LT4 4-bolt blocks have the same casting number as the 2-bolt version. They are just machined a bit differently for the 4-bolt main caps.
The bare block itself does not have a part number that I can find. It is sold in assembled shortblock configuration with 3 part numbers for 3 years. I'm assuming it is for the changes in the opti / cam dowel and CPS.
1993 - 1994 P/N 88894196 - short dowel pin, no CPS ring
1995 P/N 88894195 - long dowel pin, no CPS ring
1996 - 1997 P/N 88894197 - long dowel pin, CPS ring installed
I'm not sure if these part numbers will get a 2 bolt or 4 bolt shortblock. I know that whenver GM replaced a shortblock under warrenty they used a 4-bolt block, so I'm guessing these part numbers will get a 4-bolt but I cannot say for sure.
The bare block itself does not have a part number that I can find. It is sold in assembled shortblock configuration with 3 part numbers for 3 years. I'm assuming it is for the changes in the opti / cam dowel and CPS.
1993 - 1994 P/N 88894196 - short dowel pin, no CPS ring
1995 P/N 88894195 - long dowel pin, no CPS ring
1996 - 1997 P/N 88894197 - long dowel pin, CPS ring installed
I'm not sure if these part numbers will get a 2 bolt or 4 bolt shortblock. I know that whenver GM replaced a shortblock under warrenty they used a 4-bolt block, so I'm guessing these part numbers will get a 4-bolt but I cannot say for sure.
Last edited by TraceZ; Apr 22, 2005 at 09:09 AM.
Administrator
Joined: Nov 1998
Posts: 71,098
From: Hell was full so they sent me to NJ
Re: Need part number for 4 bolt LT1 or LT4 block
The block has a casting number..... that's where the 327 cast into it comes from. Data from the "Rebuilding the LT1" writeup:
BLOCKS
350 - There are two blocks, one with two-bolt mains and one with four-bolt mains. They both have the same 10125327 casting number, so there’s no sure way to know which one you have until you get the pan off. However, if it came out of a Corvette, it should be a four-bolt block, and if it came out of anything else, it was supposed to be a two-bolt. GM used the two-bolt block for everything but the Corvette because it had plenty of strength and it weighed a little bit less.
265 - There was only one block used for the 265 cid version of the LT1. It’s a 10168588 casting that had the numbers "4.3" cast on the side, too. It’s real easy to spot if the heads are off because of the small 3.74" bore.
350 - There are two blocks, one with two-bolt mains and one with four-bolt mains. They both have the same 10125327 casting number, so there’s no sure way to know which one you have until you get the pan off. However, if it came out of a Corvette, it should be a four-bolt block, and if it came out of anything else, it was supposed to be a two-bolt. GM used the two-bolt block for everything but the Corvette because it had plenty of strength and it weighed a little bit less.
265 - There was only one block used for the 265 cid version of the LT1. It’s a 10168588 casting that had the numbers "4.3" cast on the side, too. It’s real easy to spot if the heads are off because of the small 3.74" bore.
Administrator
Joined: Nov 1998
Posts: 71,098
From: Hell was full so they sent me to NJ
Re: Need part number for 4 bolt LT1 or LT4 block
Not necessarily. The people who designed the block knew it was getting straight 4-bolt mains, and they put the "meat" there to support them. "Splaying" can cut into areas of the block that might actually weaken it. The most powerful LT1 I was ever involved with (1,125HP on 20+# boost) used a factory 4-bolt block.
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