Quote:
Originally Posted by Bruce Lancaster
AS heads are iron. The C in the PN designates Canadian manufacture...Some Canadian aluminum heads had slightly higher than irn CR's, probably just enough to compensate for the slight power loss. There is a Canadian service bulletin page listing CC's An CR ratings for nearly all USA and Canadian heads from about '32-49
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Some AS heads were aluminium.
I have a set of 99AS heads, NOS, that are aluminum. According to the authentic documents that remain with this vehicle, they were were ordered (originally) to be installed on my '40 convertible (factory Merc. engine). It took me a LONG time to locate that set.