[tincan1966]

The blower fan has nothing to do with heating other than providing air flow. The core, no matter the size is only going to be as warm as the fluid in it- - so that is directly determined by the thermostat and cooling system, NOT the blower motor.
If your engine is only running @ 180 degrees, you will be lucky to get 130 to 150 out of the heater.

Average automotive heater output temp is around 160 degrees at the floor vent.
If you want to try to apply the "size matters" principle -our trucks heater cores are
approx 6" X 8" X 2", and rarely achieve those temps
An '88-'98 chevy truck uses an aluminum heater core that is only 1" X 5" X 7" yet they produce the heating temps of 160+

Most aftermarket heat/AC combo units have a core less than 1/2 the size of the OEM, yet they heat great.

Another misconception is that more air is more heat. Not true- you can have fantastic heat, but no air flow, therefore the truck doesn't get warm- it's not lack of heat, it's distribution. If the blower motor quits or does not run, you do not have "no heat" you have no air flow. Big difference.
Understanding how the sytem works and how to make it efficient are the keys.
I absolutley hate having to run a heater on high speed fan all the time to have heat, so I insulate well and make the system work efficiently(using the proper thermostat, keeping trash out of the air box, etc)

I know I will be argued with, but fact is fact. 25+ years of installing AC/heating units, everyday practical knowledge and hands on work prove results.

The reason why most think the core alone made huge difference- they cleaned out 30+ years of leaves, etc from the heater assy while they were in there.