Building a better world, one billet at a time

Here's how Kirkham Motorsports University, the guys that build those aluminum bodied Cobra roadsters, put a 386 pound big block of aluminum on a diet. You start the workout with 30 hours of CAD work followed by 50 hours of programming and finish with 30 hours of CNC. This exercise formula trims the overweight 386 pound block of aluminum down to a svelte 64 pounds of 427 big block.

The customer is Larry Ellison. The chassis & most of the car is also billet. An amazing project, its on Kirkham’s website.

Yes, you've seen CNC machines at work before, but this isn't just a demo, they're building a real engine and if you like engines and tools like most of us around here, it's worth a look.





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Aluminum Block to Engine Block - The reason for machining from billet is simply strength and resilience. When forming alloy, high pressure die casting is 4 times stronger than sand cast. Machining from billet is 10 times stronger. As a result, you can cut down heavy members weight by a considerable margin and still have more strength. When Harley (No, I am not a Harley fan. I ride a Goldwing) went to die casting on the Evolution engine they did not decrease the thickness of the material from sand cast. As a result, the Evo proved to be one of the best engines ever made and it took a lot of abuse in comparison to a shovel or pan. By extension, people like S&S and Murch went to billet cases which is why we have the killer strokers available today. This block is probably 1/2 the weight that a die cast would be and a third what sand cast would be and is probably able to take 3-5 five times the load without failure. If you are talking serious racing or high end cars the cost is justified by using the best.... This starts out as a forged block (billet) but gets machined down into its form. Unlike traditional forging for a finish part machining this block cuts right through any grain that occurs from the forging process. A (non porous / inclusion) cast part will have a grain that flows around the shapes, adding strength. Casting also allows for more complex shapes, if required, without special or modified tooling or where it might be otherwise impossible in a machined part.

Likely this was just done to show off the capability or a deep-pocket customer wanted it for his billet Cobra. There are new, cast aluminum 427 blocks readily available for less than $5,000.

The main frame spars on the Ariane2 Moto2 bike are machined from a 125kg block of 6061-T6 down to 2.5kg each…

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