390 crankshaft id

[390owner]

Just tore down a fe that is suppose to be a 390  Found 3u on the crankshaft is this a 390 crank?

[67428GT500]

3U- 72-76 390 truck.

[chris401]

Look at the crank flange. Half moon cut outs are all 3.3" and 3.5" strokes. 61-63 3.78" strokes had the half moon also. Not sure about the 427 steel crank. Starting with the C4AE-B crank all 3.78" and latter 3.98" cranks had the notch instead of the half moon.

[My427stang]

3U is a 390 crank as said above

[CaptCobrajet]

Outside edges of the counterweights on all 390 cranks are beveled.  The 332 and 352/360 cranks all have square corners on the counterweights.  That is the easiest way to tell from across the room.  Sometimes you get lucky.....410/428s also have beveled edges.

[wsu0702]

Look at the crank flange. Half moon cut outs are all 3.3" and 3.5" strokes. 61-63 3.78" strokes had the half moon also. Not sure about the 427 steel crank. Starting with the C4AE-B crank all 3.78" and latter 3.98" cranks had the notch instead of the half moon.

Forged steel Ford crankshafts (427 and FT) do not have any cutouts or indexing notches.  Some later cast iron FE crankshafts have a hole instead of a half-moon cutout.  All FE cast iron FE crankshafts have a small rectangular tool indexing notch. Pic courtesy of Wes Adams.