I'm not entirely sure, but would imagine these are there in part to increase the surface area to create a heat-sink. Otherwise they're just there to maintain strength whilst saving weight.. Aluminium will only corrode under specific circumstances. Simply being wet isn't one of them. Martin #1458 #4426 Original Message: ----------------- From: john fredt hecklerkochgmbh@xxxx Date: Thu, 21 Nov 2002 02:32:07 -0800 (PST) To: dmcnews@xxxxxxxxxxxxxxx Subject: [DML] engine stamping pits can you fill them? I was wondering if anyone out there has found a way to safely fill them in?If not is there at least some kind of fix anyone would suggest?