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Original Message
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| Iron/steel shafts reduce the moment arm. |
| By Dave Shoe - 03/27/2002 4:20:41 PM; IP 12.2.11.131 |
The higher modulus of the iron/steel over the stock cast aluminum design will move shaft stresses away from the center of the pedestal and closer to the rocker centerline, and will thus reduce the moment forces on the shaft.
Since the fracture of FE rockershafts originates at the weakest spot, the bolt hole, moving the stresses away from the pedestal center and toward the rocker additionally reduces the opportunity for rockershaft failure.
To be sure, if 427 racing engines of the 1960s used cast aluminum rockershafts instead of iron, there would have been a whole lot of reliability problems. Prior to the iron racing pedestals, you can be sure that Ford did run into failures.
Modern billet aluminum pedestals have the same modulus shortcomings of the cast alum items, but their massive design and additional support features tend to make up for these shortcomings while providing support for modern springs and cam ramps.
Again JMO,
Shoe. |
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