[Sleeperstang07]

I just got my 68 mustang's block back from being machined and i took a minute to look at the casting numbers they are C6AE-6015-G and under it is 7H11. Now as I understand it the C6 means 1966 but the 7H11 means August 11th 1967. There is change in compression ratio between those years so what I am wondering is: Is my block actually from a 68 or a 66 and What does that mean as far as compression ratio is concerned?

[Calponycarsmike]

C6AE-6015-G is more likely a C6AE-6015-C that would be a 289 produced between 1966-1968. That would be the correct motor for a 1968 Mustang 289 2V.

[Sleeperstang07]

I checked twice its definately a G so what does that mean I thought that just meant its a later revision of the block

[TexasAxMan]

I think the G does mean a later revision. Also, the C6AE just means a major redesign in 66.

[Ivy66GT]

That 'G's is likely a malformed 'C'. My reference says there was only one small block with C6AE letters and it was, as Mike described, used for years 66-68. It was cast in the Windsor foundry.

Compression ratio depends mostly upon the pistons and head used and not the rev number of the block. The engine change level has more to do with the details of what they did and that for the 66-68 time period was anywhere from change level 10 to 16. The change level was (is?) on the Al tag attached to the engine.