Does a steel crank have better harmonics than a cast crank?

Old 05-13-2007, 04:15 PM
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Default Does a steel crank have better harmonics than a cast crank?

The local engine builder told me that a forged steel crank
besides having less chance of breaking over a cast one
also has what
he calls better harmonics.
Anyone evere heard of this ?
Is it rue ?
keb1 is offline  
Old 05-14-2007, 03:44 AM
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Actually he is mostly correct.

The steel cranks can handle the damaging harmonics better as they are more ductile. A crankshaft is literally trying to tear it's self apart as it is operating because it twists and flexes with the pressures of each cylinder/piston/rod combination. It li9terally twists back and forth all the time. That is what a Harmonic Dampener is for is to be like a shock absorbing action to resist agaist the harmful twisting harmonics.

A EN 303 or even 4340M USA Forged material will be slightly more ductile than a 4340 USA Forged material will be. Next will be the import 4340 material or the USA Forged 4130 material. I guess next would be the 4130 import material and the USA 5140 material. The import 5140 material is not as strong or as resilient as the factory USA Forged Steel in the cranks. Very close to the 4130 and 5140 material is the Nodular Iron material used in Factory OEM Chevy 400's and the Factory High Performance Fords. Last is the cast iro9ns and the cast steels sold from import sources.

The previous paragraph is only my opinions from years of experiences but with no proff to back it up.

A crankshaft if spun all by it's self would exhibit if measured harmonic forces. I am only guessing that a cast crank would show less harmonics at a given rpm with nothing attached to it. My logic is it is stiffer and is more brittle, so would emit actual harmonic sounds at different rpm.

edvancedengines is offline  
Old 05-14-2007, 07:25 AM
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Location: The Custom Engine Shop, Indianapolis, Indiana
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A lot of good info Ed posted there.
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