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Basics of Crankshaft Manufacturing

The Fundamentals

Comprehending the fundamentals of crankshaft manufacturing and machining can be extremely helpful in not only maximizing performance, but in improving crank and engine life.

The supply of suitable junkyard crankshaft cores, once a mainstay of racers everywhere, has pretty much dried up, but performance enthusiasts now have lots of sources for brand-new, reasonably priced cranks for Chevrolets as well as popular Ford and Chrysler engines.Crank Shaft dark background

One of the very first things beginning engine builders typically ask is: what is the very best crank to utilize, forged or cast? A cast crank is just that; an iron casting in which the metallurgical structure is made up of a random pattern of particles, filled with tiny holes and spaces. A forged steel crank is produced by compressing a much purer metal into the die under severe heat and pressure to produce an extremely dense molecular structure, and a much stronger crank.

This forged crankshaft from Eagle is created for small block Chevy applications. It’s reasonably easy to spot the difference between a cast crank and a forged one. Cast systems have a distinct parting line located on each of the counterweights and throws while forged units can be identified by a wide, raised die mark on the throws. The only weak points of a conventional basic forging is that during the manufacturing process, the connecting rod throws are offset by twisting the crankshaft. Twisting not just misshapes and stresses the forging, but likewise restricts the kinds of metal that can be used.

Shop OperationsCrankshaft

As soon as the kind of crank has actually been figured out, there are a number of machine shop operations that can be carried out to make it more durable, and to validate that the crank picked is suitable, particularly for racing use.


Magnafluxing is a crucial step in the crankshaft manufacturing and selection process. It is a dry, non-destructive test in which the part goes through a strong electromagnetic field while magnetic particles are sprayed on the surface area. Any cracks act as magnetic poles, causing the particles to line up along that point. Any cracks aside from small stress cracks surrounding the oil holes are grounds for rejection.crankshaft install


Magnaglow is a wet, non-destructive test throughout which the part is covered with a liquid containing magnetic particles. The part is then subjected to a strong magnetic field which triggers the particles to line up along any cracks that may exist. An ultraviolet light is used to find the particles and the cracks.

More Methods

In crankshaft machining, turning, or grinding, includes machining the journals undersize to fix scored or damaged bearing surfaces. Use of an undersized system is of no issue and as long as the crank has actually been turned properly, it will keep the proper oil clearances. Some racers will intentionally “turn” a crank as much as.030″ or.040″ undersize in pursuit of a smaller bearing size that allows them to squeeze out a few more “horses”.

crankshaft grindingA typical practice includes machining the rod journals of a small block Chevy crankshaft to 1.888″ so that smaller Honda-sized rod bearings may be used to maximize performance.

Indexing makes sure that the rod throws are precisely 90 ° apart. Stroke monitoring is performed to see that each rod throw has the same stroke and can likewise be remedied during the indexing process.

Offset Grinding

Offset Grinding is a typical practice used