These cranks are less expensive than 4340, but you still get all of the advantages of having a forged crank.
The line “how fast do you want to go?” is a question that applies quite well, not just to the racing market but the car hobby in general in terms of how much money one can or should spend on components. But the desired life of your engine is quite dependent on how much one spends as well. And for those constructing a high horsepower rotating assembly, 4340 forged steel crankshafts are often a wallet-killing, yet necessary purchase. But thanks to manufacturers such as Eagle Specialty Products, quality doesn’t have to come with a painful price tag.
We stopped by the Eagle Specialty Products booth during our tour of SEMA, where we were given the 311 on Eagle’s new 4140 steel crankshafts for both Small Block and Big Block Chevrolets. These cranks are fully forged from SEA steel with a non-twist forging, multi-stage heat process, stress-relieving, and surface hardening for increased strength and durability. These new 4140 cranks are designed for applications that demand more than a cast crank while on a tight budget.
“These cranks are less expensive than 4340, but you still get all of the advantages of having a forged crank,” explained Eagle’s Robert Loftis. “By forging the 4140, we’re able to bring the cost of a strong, quality product down considerably for our customers.” Each journal in these cranks is micropolished to an incredibly fine 3 r.a. point or better, while a .125-inch radius is used to increase strength’ thus chamfered bearings must be used. They are designed for internal balancing and for applications up to 1,000 horsepower. The BB cranks measure 4.250-inch stroke, the SBC part is 3.750-inches.