Dum ass me don't know how to tell the differences.

Can someone explain how to tell the difference.

Think I might have a 312 steel crank

Many thanks,Oldmics

Easier to show you the difference, I think, than to describe it, John. Short answer... the parting line. Let me explain...

CASTINGS

Metal castings are made in a mold, and most molds have sections that fit together to create a cavity for pouring the molten metal into, to shape it. For Ford y-block cast crankshafts, I think two mold sections that fit together were used to make the mold with the shaped cavity inside. The two mold sections were made of sand conditioned with water and clay.

Where the mold sections fit together, when the metal fills the mold cavity there is a continuous narrow line in the finished casting. The line is referred to as the ‘parting line’,i.e., the point where the mold sections met. Basically, molten metal filled the line where the mold sections came together.

Sooo… look for a narrow line (like a pencil line) usually appearing on the crankshaft counter weights from front to rear.

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FORGINGS

Metal forgings are made in molds, too. The difference is that the metal to be shaped is only heated to make it soft (‘plastic’) so that it can be squeezed or hammered into the desired shape between two shaped metal molds (dies). For complex shapes like a crankshaft, a series of metal molds (dies) are necessary to progressively hammer the metal ingot (chunk) to the new desired shape. Each set of molds (dies) furthers the shaping process to refine the shape as much as possible before machining is required to attain the final shape.

Because the metal being forged is only soft, not liquid, the metal molds (dies) never come completely together in hammering the metal ingot (chunk) to shape. Because there are two molds (dies), there again is a parting line on the crankshaft. In the case of a forged steel y-block 292 crank,the parting line is ½ an inch wide in some places and wider in other places. The parting line is not in a straight line from front to back as it is with the cast crank. One place to look for the wide parting line is on the first throw after the front main bearing. The parting line is in the middle of the outside of the throw.

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Generally, forged parts are stronger than cast parts. The grain structure in a cast metal piece is random. The grain structure in a forged metal piece is designed to flow with the shape of the part in a chain-like manner. Too, the squeezing or hammering of the metal into shape compacts (compresses) the metal grain structure so that it is denser than a cast piece. Per volume, a forging weighs more than a casting.

A forged part costs more to make than a cast part. IF a metal part needs to be of minimal size yet as strong as possible, forging is likely the forming method used… like in making hand tools.

Hope this helps.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

In addition to what Charles said, the surface finish of the forging will typically be smoother than a casting. Also the alloys are completely different, the forging is steel, while the casting is grey or nodular iron.

Frank/Rebop

Bristol, In ( by Elkhart) 

292 forged cranks do not have counterweights adjacent to the center main journal. I would assume that a forged 312 crank also would not have those counterweights.

John - "The Hoosier Hurricane"

The oem cast crankshaft will have eight counterweights while the factory steel crankshaft has only six counterweights. As John mentions, the steel crankshaft does not have any counterweights at the center main journal.

Lorena, Texas (South of Waco)

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Wher was the forged 312 crank used?

Frank/Rebop

Bristol, In ( by Elkhart) 

AussieBill's picture of the forged crank clearly shows John and Ted's earlier point that there are no center counterweights. The picture also shows how the ends of the counterweights on the forged 292 y-block cranks are rounded.

NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Good luck if you have, been a bit of talk of them existing lately rather than maybe,s. Measure the mains 1st then check the counterweights explaned further along in this post.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

John. Have you measured the main journal diameters? This would help to verify what you have if the crankshaft is indeed forged steel and not cast iron.

Lorena, Texas (South of Waco)