What is the stock heater blower fan rated at forCFM ?

I've been looking at a 320 CFM blower on-line that could give t bigger push. I barely feel air movement under the existing blower set up.

Here's a pic of the one I'm looking at:

https://www.amazon.com/gp/product/B01MRD344...pf_rd_i=desktop

Jim,
There should be no need for anything bigger than the stock fan, I used to drive my car in the coldest NYC weather and was always warn in my car.
Most problems arise from missing or ill fitting parts and gaskets.

There are these, what I believe were asbestos gaskets sealing the engine fan heater output, someone makes them in rubber, a good number of engines are missing the "backdraft" flaps and the previously mentioned gaskets, that prevent the hot air from the heat exchangers to be circulated around the engine.

Make sure all heated air pipes are secure, use the 2 output fan that blows air to both exchangers.

Nothing like a cold day with the top off and the heat on!

Spin the wheel by hand. It should rotate freely. Easy to take out and bench test. Check for full voltage in the harness to the motor. Field could be worn out in motor.

My fan doesn’t work and the car gets too hot to leave on high in freezing weather. Cracking the window actually works to let more hot air in.