OSK/T

If indeed the pistons are 3.062" diameter (3 1/16") and the date of the serial number is for a '46 the block may be a "carry-over" engine from 1941. The reason there are no Fords/Mercurys from 1943-1945 was because Ford Motor Co. was making jeeps and other WWII machines. Ford often carried over parts left over from a previous year to the next year where possible. The 1941 Mercury blocks were 3 3/16" bore V8s compared to the Ford 3 1/16" in 1941 but after WWII the same block was used for Ford and Mercury from 1946-1948 with 3 3/16" bore and 3.75" stroke. If your pistons are 3.062" for 3.0625" bore that means your block has not been overbored and that is good since overboring usually leads to an engine which will overheat! My guess (which may not be correct) is that your block is a carry-over 1941 Canadian Meteor block if indeed it is of 1946 Canadian origin. If this block is cleaned up and found to be free of cracks it is a gem! Just put a 3/4 cam in it maybe a dual carb manifold and look around for a 4" Mercury stroker crank in it (1949-1951 Mercury). I have one for sale but by the time I box it up and freight it you might be better off to look at a stroker crank from Speedway Motors in Lincoln Nebraska. Other good news is that there are already shallow relief cutouts in the block between the valves and the bore which could be enlarged with a grinder for a little better breathing but overall don't expect to get more than 150 HP out of it with a reasonable possibility of only 120 HP even with those beautiful (but now expensive) finned aluminum higher compression heads. In the 1950s a 120 HP flathead with a 3.78 rear would have been considered "a warmed over" street rod. Still the low gear acceleration was pretty dramatic up to about 40 mph with just a standard 3.78 rear and better with a 4.11 ratio rear.

Best Wishes,
Don Shillady
Retired Scientist/Teen Rodder