We could (and have...) spent a lot of time debating and discussing the comparative merits of 2618 versus 4032. Randy is closer to current technology, my data would be somewhat dated at this point.
The silicon content of 4032 has some advantages that were very important to OEM automotive and marine applications. Silicon improves durability of skirts, pin bores and ring grooves for extended use applications. The 2618 has greater high temperature strength and ductility - important in a race environment where a part may run at - or even beyond - it's design envelope. The growth rate is different, but skirt clearances are at least as dependent upon oil groove drainback design and skirt profile as they are on materials. Modern design capabilities, tuning ability, and coating technology allow the differences between the two materials too be minimized if not completely adapted for. I have seen 1000HP+ 4032 engines and 70,000+ mile 2618 builds, neither of which were imagined possible 20 years ago.
