I think i ran onto a 4"merc crank and want to positively be able to i.d. it.It has 2" wide counter weights and a 7/8 hole in the rear counter weight.Also on the end of each counter weight it says 1CM, could that mean Canadien Merc?Any help appreciated.
"CM" on the heads shows merc, I believe. So I would say it would probably be the same on the crank http://66.154.44.164/forum/showthread.php?t=116415 heres another: http://66.154.44.164/forum/showthread.php?t=139305
1CM means it is a '51-53 (American) crank with pilot hole in back for the front of a FordoMercoMatic...will be fine with stick too. Earlier cranks not numbered, so: First check to see 2 holes in each rod throw, cleanout plugs. Test will give wrong answer it it's an early crank! Then lay a 6" rule across front counterweight at widest point...Ford less than 6, Merc a bit more. Next...measure rod journals to see if it is a stock 4" Merc or Merc with small journals offset ground to make it 4 1/8. Necessary because need different pistons. Apparently there are variations (rare) out there, so cleanout size is perhaps not 100% certain ID.
Except... There are exceptions, Merc cranks with Ford sized cleanouts. They are allegedly Canadian production... Measuring the weight seems to be reliable, and if you have a wall, a yardstick, and several chunks of 2X4 you can measure actual stroke, crudely but well enough to tell the difference. The 1CM crank is of course a certainty as a Merc, but you would want to investigate the possibility of the common offset grind.
Would you give a clarificlation of a cleanout hole?There is a 7/8 hole in the rear counter weight that is perpendicular to crank centerline,is that a 'cleanout hole'?It appears to be a forged crank.
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