This is not a discussion of the qualities of crank manufacturing, or a benefits analysis of cast cranks vs. forged cranks.

This is simply a brief to highlight the distinguishing physical differences between the cast cranskhafts used in the earlier years 3000GT/Stealth and the forged crankshafts used later. The 3000GT and Stealth went through a number of crank shaft part numbers, making the change from the cast version to a forged version starting in model year 93 (June 92 and later production dates). As of several years ago, the cast crank is no longer an available option through Mitsubishi, making the stronger forged crank the only available crank for the DOHC 3000GT/Stealth (whether turbo or not). The current forged crank is "backwards compatible", working in all years of the DOHC 3000GT/Stealth engines and we keep them in stock for quick shipment.

NOTE: The SOHC 3000GT and Stealth carry different part numbers for their crankshafts, and use a physically different crankshaft.

The cast and forged cranks are actually very easy to tell apart. There are two distinguishing factors that separate them at a quick glance:
1) The 91-92 cast cranks have casting seams along some of the surfaces - the 93-99 forged cranks do not have these seams.
2) The 91-92 cast cranks' center balancing lobe is rectangular coming straight out of the center of the crank - the 93-99 forged cranks' center balancing lobe is rounded, like a big teardrop shape.

These pictures highlight these differences.

Cast on top, forged on bottom.

Cast Crank on left, Forged Crank on right

Forged Crank on left, Cast Crank on right
Notice the big seam in the large lobe on the near end of the cast crank on the right - that is a casting seam.

Forged Crank on left, Cast Crank on right.
Notice on the cast crank on the right the center lobe is rectangular, coming straight off the centerline of the crank, while the forged crank on the left has a more rounded center lobe.