Someone wrote:
Another thing you might want to check is that you put the little cooling
tins back under the cylinders.  I'm talking about the ones that snap in
between the studs and cause air that flows down between the cylinders to
be diverted around the lower parts of the cylinders rather than just
blowing out the bottom of the engine.  The first time I had my engine
apart I forgot to put these on until I had the heads torqued down, and I
couldn't get them on without removing the heads at least part of the way.

My Question: 
There was a mention that all of the cooling tin was important.
Well I have a 76 Type II which I believe has a Type IV engine.
I know there are two peices missing on my van, and will try to 
describe them here hooping someone can tell me the importance
of these pieces.
The stainless pipes that come out of the cylinders, and joint them to the
rest of the exhaust (on a watercooled car these would be the cast iron
exhaust manifolds) cracked. I had a mechanic get them welded. When
he was showing me what he had done, there were four crumpled tin things
on the shop floor that looked like they went over these 'stainless 
manifolds' like some sort of little shroud. When I asked if they were to be
replaced, he said no they are not needed. They were sort of half curved
pipes, two of which would go around the 'manifolds'. What are they? What do
they do? What happens if I don't have them?
Also anyone know why the 'manifolds' cracked? The mechanic said that he had
never seen this before.
Sorry about the vague description, but the van was new to me, and
I really didn't have a good image of how all those tin bits went together.

Thanks for any  help.
Bill Crick
76 Type II/IV/VII
Ottawa Canada