I was close, so close… Well ok, I had the correct manufacturer.
Thanks to persistence of DeadinSide and with the help of Daniel & crew over at Hemmings, the mystery has been solved.
It appears to be an early 30’s Cadillac 353. While I cannot be certain Mystery Motor came from a 1931 Lasalle the shape of the frame suggests that it could have. After a little more digging around I also found a 1930 Cadillac 353 Victoria Coupe that also fits the bill nicely.
Thanks to everyone for helping to track this down and if you have any other weird/rare/bizarre motor photos drop us a line.
Tim Odell 
Robert Emslie
Now I can sleep at night. Ahhhhhhh.
Thank you!
So what does HC stand for? High Compression?
Horribly confusing
Hand Crank?
It's the Cadillac of sluice mine pumps.
You're welcome [thank Dan @ Hemmings for putting it up] – glad the internets came through this was bugging me, a lot.
Oops sorry! Meant to go back and add you in there. It's fixed, thanks!
Haha, no worries, just be cheeky.
Yeah Hemming's, as well as Hooniverse, has some very intelligent hoons as followers…
Thanks for getting to the bottom of this. It was bugging the hell out of me for a couple of years, since I went to Ruby. I had no doubt that some Hoon would know how to get an ID on this thing. Next time I go to Ruby, I'll print out a copy of this post and show the guy there what it is. He told me it was a Ford, which I knew was hooey from the second I laid eyes on the thing.
It's my engine mystery solved. God, do I have to teach you people everyt–
…
…never mind.
I LULZed
Thank you mysterious unnamed commenter and Hemmings! I bet the Hemmings guys had a blast with this. That site's readers have a plethora of obscure knowledge about cars long relegated to the dust heaps of history.
As a longtime subscriber I can assure you that many of their readers have also been so relegated.
I love the automotive obscurantism on Hemmings and the knowledge of the readers, esp about pre-WW2 stuff.
They do, which is fantastic since pre-Depression nearly every major (and some minor) US cities had their own car company. Many would operate for a few years then get bought or close shop. And there's usually someone on Hemmings that knows something about one of these tiny outfits and the 2 or 3 cars they built.
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