OK so my block has casting number 2463430 on it which I understand to mean 1966 - 225.

So then what does the number stamped into the block on the edge of the head (#1 cylinder)surface mean?

AL-HP-196614C

Well, no, not exactly. That's the casting number for '63-'67 RG (tall, 225) engine blocks.
Your car appears to have had an engine swap at some point in its past, and the replacement engine came out of a big '65 Canadian Valiant. Its number decodes as follows:

A: 1965 model year

L: 111"-wheelbase car (Canadian Valiant Custom 100, Custom 200 or Signet)

HP: High Performance engine option (225 instead of base 170)

196614C: Engine serial number


The original 225 engine in a '66 Canadian Valiant would be stamped similarly to this:

B225 8-1 2

B: 1966 model year
225: engine displacement
8-1: example date
2: example signifier of the particular engine production line

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thank you Dan. You are a wealth of knowledge.

So it looks like a Canadian Valiant sacrificed its power train to get rebuilt, and installed in a 65 Dart/high school project. Alas the Dart was in a collision, and wrecked before rebuilt engine/trans could be installed. The engine/trans sat in the corner of a shop for 11 years sealed up tight, and wrapped in plastic. Waiting to be purchased for pennies on the dollar. Then live out it's remaining days in a 1964 Canadian Valiant convert with all the tricks and goodies I could find off this site.

I love this place.

You're welcome. Sorry, I misread your post and the idea of a '66 Valiant crept in. No engine-swap mystery, then.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.