# Help with 400 engine ID



## FB68 (Aug 1, 2010)

I have a 400 engine that will be rebuilt shortly. I was reviewing the engine codes again and there is one that doesn't match, thought you all might help.
The casting number is 500557, which makes it a 1975 late or 1976 400.
The date code by the distributor is C176, so it is in fact a 1976 engine.
Here is the problem, the engine code at the front passenger side is "XZ".

In all the engine number deciphering sites I visited, I can't match the rest of the data with "XZ".

Anyone have suggestions??


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## pontiac (Mar 6, 2011)

bet it is X4


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## 68greengoat (Sep 15, 2005)

1976 400 170 HP (Late) *XZ* A 7.6 555 6X 1-2 17056160/64 Block Casting # 500557


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## FB68 (Aug 1, 2010)

Thanks 68greengoat! The 6X I know is a designator for the heads. What is the A 7.6 555 mean, followed by the 1-2 17956160/64?


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## 68greengoat (Sep 15, 2005)

FB68 said:


> Thanks 68greengoat! The 6X I know is a designator for the heads. What is the A 7.6 555 mean, followed by the 1-2 17956160/64?


A - Auto trans
7.6 - compression ratio
555 - cam
1 - 2 = 1, 2 barrel carb
17956..... - carb#


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## FB68 (Aug 1, 2010)

Thanks!


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