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Currently rebuilding an early Cooper S engine and hope that someone can help me figure out the approximate production date. The tag on the engine reads 9F/SA/Y/38907 .

Hi Don. Welcome to the forum.

That engine would be mid October 1965 I think.

Here are some others in a similar range:
[38678 built on 6 oct] https://bringatrailer.com/wp-content/up ... 163616.jpg
[39769 built on 26 nov] https://bringatrailer.com/wp-content/up ... G_7060.jpg

Pretty sure the date code is cast into the block showing Shift/day?/Month/year.
I'd be interested to know what yours says as it's something I'm researching. I've asked around, but no- one seems to reply.
Paul

Engine likely came from the production lot of Cooper S's with chassis numbers ending with 799XXX (like mine). My original, long-departed engine was 38810 (14 October)--now has an early, thick-flange 12H/397F block w/many of the original accessories installed.

For what it's worth, 767XXX was the previous block of Cooper S car numbers and 820XXX was the succeeding block...

HI TECH396

I have a block hear (no engine No', it has been bored) and has D21J6 cast on the back of the block, any Idear of build date and engine size/car

sorry to but in

regards mike