I'm trying to determine wether I have forged or cast pistons in my small block. All I have is the rebuild invoice parts list which shows "hypereuth... pistons" ( can't read the rest). Does this indicate which type they may be? Thanks all !!
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Re: pistons ?
Sounds like you have hypertutenic (sp?) pistons, which are neither forged nor cast but a relatively new process. Supposed to heve most of the strength of forged without the manditory loose fit of forged. "Best of both worlds" sort of thing. -
Re: pistons ?
james-----
It's "hypereutectic" and that's likely what the reference on the invoice means. If you had the piston manufacturer and/or model number I might be able to tell you more about them.
The term "hypereutectic" refers to a high concentration of silicon in the aluminum alloy that the pistons are cast from. This high concentrtation makes the piston material much stronger than lower silicon concentrations ("eutectic"). The problem is that it is difficult to disperse high concentrations of silicon in the molten aluminum alloy. Until processes to do this were invented, "hypereutectic" alloys were not possible. That's why they weren't used before the 1980s.In Appreciation of John HinckleyComment
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