On my old KB Hemi, I had to set the valves cold at about .005 and that was at 70* or more. Once warmed up, the lash was usually in the low .020s, depending. And I certainly didn't try to start the engine below 60* or so. In other words, I couldn't set the valves to the spec card hot, I had to set the valves at .005 at room temperature and live with whatever it ended up at hot because the engine would grow almost .020.

After having that experience, I went with iron on my current engine. Although I don't care for the extra weight on the nose, I just didn't want the issues that aluminum brings to my primarily street car.

And one last thing, I did drive my car a couple of times this winter on nice 50* days. I wouldn't have even tried that had the engine been aluminum.