Eagle 4340 Steel Cranks

The 4340 forged steel crankshafts from Eagle Specialty Products are great for high performance or racing applications. They feature non-twist forgings, go through a multi-stage heat-treatment process, and are stress-relieved and shot-peened. These cranks are X-rayed, magnafluxed, and sonic-tested. Each crankshaft is cross-drilled and has chamfered oil holes for improved oiling, a .125 in. radius on rod and main journals for increased strength, and the journals are precision-ground and micro-polished to less than 5 R.A. Target bob weight of +/- 2% greatly reduces balancing time.

All Eagle 4340 cranks are forged from certified 4340 chromoly steel. While a lot of companies make cranks from this material, if you pay close attention, you will notice not all 4340 is the same. For instance, to be classified as "4340 steel" certain alloying elements must be present in certain percentages. AISI/SAE specifications call for 1.65% to 2.00% nickel content. While this seems like a small difference, understand that this is almost an 18% variation. 4340 steel with 1.65% nickel will act a little differently than 4340 steel with 2.00% nickel content. This is just one of many alloying elements involved in creating 4340 steel. Through extensive material testing, Eagle works closely with the foundry we use to achieve a much tighter tolerance of all alloying elements to our specific requirements. Along with this, the heat treatment and tempering process used is vital to producing a stong steel. While exactly what Eagle does is a closely guarded secret, all of this attention to detail results in a stronger and much more consistent material. Eagle "4340" steel routinely tests 10-15% stronger than "typical" SAE/AISI spec 4340 steel.