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Old May 10, 2018 | 11:45 AM
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Default engine block question

Hi guys. I'm up in Seattle (rain) helping a friend rebuild his engine. He thought it was a 350 but the casting number says different. 391660 in Mortec says it's a 68 327. My question is this; the threaded hole in the block in front of the fuel pump rod is not there, it's just a cast solid. When did GM stop/start drilling this?
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Old May 10, 2018 | 11:59 AM
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Some blocks in the late 60's and early 70's did not have a hole drilled in that location. I never knew for sure why though.
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Old May 10, 2018 | 12:09 PM
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Thanks, learn something new every day. Or senility is setting in.
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Old May 10, 2018 | 12:48 PM
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Originally Posted by MasterDave
Thanks, learn something new every day. Or senility is setting in.
I have a 65 327 250 HP block from a passenger car in my 37 Chevy coupe.

While changing the fuel pump a year or so ago, I too discovered that it was not, nor had it ever been drilled and tapped for the "retaining" bolt.
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Old May 10, 2018 | 12:56 PM
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I always thought that maybe all the Flint castings had the hole drilled/tapped but maybe not all blocks from Tonawanda? I don't know.
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Old May 11, 2018 | 04:06 PM
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Originally Posted by MasterDave
Hi guys. I'm up in Seattle (rain) helping a friend rebuild his engine. He thought it was a 350 but the casting number says different. 391660 in Mortec says it's a 68 327. My question is this; the threaded hole in the block in front of the fuel pump rod is not there, it's just a cast solid. When did GM stop/start drilling this?
As you may already know, there is no functional difference between the block of a '68 327 and the block of a '68 350. Both had large-journal mains and a 4" bore, but the 350 crank had a longer stroke.

So, if your friend doesn't mind buying a new or used 350 crank, that engine could become a 350. Note that the pistons would also have to be changed if your friend wasn't already planning to replace them.
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