Re: Polish aluminum engine

Posted by Don Shields On 2014/2/9 18:01:08

Actually the cylinder blocks on these engines are iron, not aluminum. The crankcase and oil pan are cast aluminum with a somewhat stippled, non-reflective surface as supplied by the foundry. Packard left these castings unpainted and unpolished. Over the years a coating of oxide forms on these castings that darkens and dulls the surface. It can largely be removed with drill-mounted wire brushes with the engine still in the car. The wire brushing will leave the castings with a brighter but certainly not a polished-looking finish very much like newly-cast aluminum. Oxide will begin to re-form on the surface although it could be some time before it is highly visible. To prevent or at least slow down this oxide process, something like Eastwood's Diamond Clear finish for bare metal can be sprayed on the castings. I've seen a 1930 726 engine done this way, and it looked more authentic than the commonly-found aluminum-painted restorations. I wouldn't put any kind of coating on the inside of these castings.