On Jan 18, 1:31 am, Scott Braddock wrote:
Second, install the winter baffles on the
cowl openings, which prevent a lot of cold air from blasting against the
firewall.

Winter fronts don't keep cold air off the firewall. They reduce the
airflow over the cylinders so that the engine can run warmer. The
airflow onto the cowling goes through the cylinder and head fins and
out the bottom of the cowl; there is little cold air that reaches the
firewall at all.

Cabin heat comes from the muffler. Air enters a small scoop just in
front of the engine in one of the cowl inlets and directs air into a
hose that connects to a shroud around one muffler, and then out via
another hose to a valve on the firewall that wither dumps this warm
air overboard or lets it into the cabin. Any defects such as a missing
air scoop, torn hoses, loose shroud, or a valve that isn't properly
closing off the dump port (and all of these are common problems) will
make cabin heat ineffective. Many 150s have both mufflers plumbed in
to increase the heat available. Still, a 150 was an inexpensively-
built, poorly insulated, drafty little all-metal airplane, and it will
never be as comfortable as the cheapest car available. The older 172s
aren't much better. The new 172s are far tighter and better-insulated.

Dan