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I was wondering if somebody could tell me how to tell the difference between a 360, 390 and 428 crank. How do you measure the stroke or is there a number on the crank somewhere. I couldn't find one on a possible 390 crank. The paper tag at the junk yard had 360 scracthed out and had 390 written under it. Thanks for your help.
The stroke is equal to twice the throw. The throw is the distance from the centerline of the crankshaft to the centerline of the rod journals. If you have a good set of calipers, you can take the measurements. Remember to compensate for the fact that the crank and rod journals may be different diameters. Measure the distance from the outside of a crank journal to the outside of an adjacent rod journal. Add 1/2 the diameter of the crank journal, and subtract 1/2 the diameter of the rod journal. The number you're left with is the throw. Throw on a 352/360 crankshaft is 1.75", and throw on a 390 crankshaft is 1.89".
360 cranks have a 2T on the # 3 counterweight.
390 cranks have a 2U on the # 3 counterweight.
410/428 cranks can have a C6ME, 1U, 1UA or a 1UB on the #7 cheek. The 1UA crank may have a B on the # 1 counterweight and the 1UB crank may have a A on the # 1 counterweight.
I don't mean to disagree with the bulk of what has been posted in reply to your question but I can definitely say not to pay to much attention to the notches in the flange end.I have both a 360
crank and a 390 crank that look identical at the flange end.Casting numbers and direct measurement are the best way to tell what you have.
I can throw some more shadows on these methods of ID as I have a known 67 410 that has no marks on the crank except for casting flash. So the only true method is to measure it.