Head Material

[Ed Curtis]

I noticed GM changed the aluminum alloy for these heads. Is this a new trend for all GM cylinder heads?

Ed

[OldSStroker]

I noticed GM changed the aluminum alloy for these heads. Is this a new trend for all GM cylinder heads?

Ed

Here is a link to a GM casting design presentation on blocks, but it applies to heads also.

http://www.sfsa.org/tutorials/eng_block/GMBlock_11.htm

Note that "Pressure tightness" of the 356T6 is rated the highest as are tensile and yield strength. The LS9 head is 356T6 and uses "spin casting" to help eliminate porosity. Spin casting, once you pay for the tooling to do it, is probably considerably cheaper than HIP or Hot Isostatic Pressing which Edelbrock uses (at a premium cost) on some of their head castings to minimize porosity.

I think GM will only use the 356T56 when the application needs it. They might be increasing the use of spin casting, but I haven't seen it in print.

Jon