Cleaning out Duster Cowl Vents...

Mike,
Take a look at this post from "slantsix.org" some time ago. http://slantsix.org/forum/viewtopic.php?t=13106&highlight=cowl
I added some pics to explain where the drains are that get clogged up with debris, causing leaks into the cab. An air line, as stated above, is a good way to get the bulk of the trash loosened up and flying about, so you can vacuum it up. However, I was amazed at the amount of junk that accumulates over 30 years, if not routinely cleaned out. These drains will get packed with leaves, stems, acorns, etc., until they look like birds were nesting in your cowl. I used needle-nose pliers, bent wires, and an air nozzle to clear them out. If you flush with water, you might want to use a gentle stream, not a high pressure blast. Look at the picture showing the fresh air inlet into your dash. It's not a very tall lip that water has to wash over, before it enters your air box.

Jerry