What was?

Spaceage material no.2 ?

Obviously it was the material created after Spaceage Material no. 1

Try again: What was named spaceage material no.2 by the Harley-Davidson racing dept.What parts was it used for and what was an ingredient of it.

Just wild guessing big time on this after a lot of thought.
Aluminum - crankcases - bauxite?

Heres another hint;If you go to page178 of the book MOTORCYCLE ENGINEERING by Phil Irving.You will get a major clue.Im thinking this may have been the source of Harley getting this idea.I have the 5th edition which is copyright 1973 so the basic info is earlier than that.

See page 138 of the book HARLEY RACERS byGirdler.

I don't think I would be spending my money on anything Girdler wrote.

Its not a bad book.Probably worth it for the pictures even if you dont like the text.Try to stick to answering the question instead of being a critic of something you did not read.

Who said I haven't read it?

Aluminium with high silver content (sic)
Stéph

Page 138 "Harley Racers" Hmmm

I'm with Stéph

I have always enjoyed Girdler & Sporty's

Also have a copy of Irvings "Motorcycle Engineering" I got in 1964. How about his 1959 "Tuning for Speed"

I don't think I would be spending my money on anything Girdler wrote. - C. Haynes

The Harley-Davidson and Indian Wars was a very interesting book, though not about "wars" between them, more like parallels between the two marques. The book was written in 1997, but IMO, has amazingly contemporary context. In so fact so, that it seems to have been written more like in the 21st century instead of the latter part of the 20th.
I'm sure you have some reasons for not liking the book, so please qualify your statement tell us what you didn't like. Maybe I missed something
As far as space-age materials.....you must mean fiberglass. Plastics!...think....plastics!

Thank you Steph for putting my one and only attempt at trivia out of its misery.The heads and barrels were aluminum alloy with a silver content.I imagine this is for thermal conductivity.That was the purpose for the idea of an all silver head in the Irving book anyhow.