what exactly is it?

Ian

tinware is used to separate the hot parts of the engine from the parts that you want cooler and to deflect cool air onto the hot parts and they look like this http://www.oldbeetle.de/intl/pcat/T1_12.html  hope this helps,later.mick.

thanks Mick...now I know and I can act informed when people mention it.
cheers, ian