Re: AMC Pistons; Forged have downsides too , Cast has advantages ...

[ortfamily@xxxxxxx]

With pistons, it is cast or forged. Cast parts are just that, hot metal poured into a mold and cast into a piston. Then it is machined to the correct size. Forging involves pounding the hot metal into the mold, then machining. Forging consolidates and compacts the material and results in a stronger product.
Cranks are a bit different. They are cast iron or steel. Steel is much stronger but is not necessarily needed on a normally aspirated street engine that is fairly stoutly built and runs at 5 or 6 thousand rpms.
Or so I see it, maybe I am full of it.

On September 23, 2004 andrew hay wrote:

> i believe it wasn't until the '60s that an acceptable cast iron crank
> was even possible.  i'll bet gm's 'armasteel' first appears around
> then.  i wouldn't be surprised if it didn't come down to a new process
> for volume casting high-strength iron.
> 
> " It takes a lot of testing to see if a cast crank will be strong enough. That's the reason forged crank and rods were used in the first 390. The SAE papers on the engine specifically state that there wasn't sufficient time for testing a cast crank. The 390 and 401 were produced in relatively small numbers when compared to the 304 and 360. My only conclusion can be that once the tooling for the forged parts were in place there wasn't enough volume to justify testing and new tooling for a cast version.
> 
> this makes a lot of sense.
> ________________________________________________________________________
> Andrew Hay                                  the genius nature
> internet rambler                            is to see what all have seen
> 
> adh@xxxxxxxxxxxxxxxxx                       and think what none thought


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