Check out these pictures of the swap:
PICTURE new motor, old motor, heater core PICTURE new motor installed, front view PICTURE new motor tag and info PICTURE installed with fan on PICTURE wiring and view from back The new motor just slid right in the heater core/housing. I had read about slotting holes to make motors fit and at least with this combination that is completely unnecessary, just bolts in as easy as you please, zero modifications.
Yes the direction of the motor can be reversed by changing polarity (switching wires).
Not sure why the motor tag specifies "clockwise" when it definately will run either way. I won't get into explaining which wire is grounded because for one reason GMC trucks were positive ground, so different answers for Chevy and GMC. Then if for some reason different heaters use a different direction fan that would change the answer again.
Simple answer is "wire it so it pushes air out the vents".
The last picture you can see a little detail I thought of for the wiring. Used a male spade terminal on each wire. Then on one of the spare motor studs slipped a female spade "flag terminal" connector over it and clamped with a nut. Now just plug in one or the other leads as needed to ground and connect hot wire from heater switch to the other. This is simple and effective and most of all requires no tools to change polarity when I switch to 12V negative ground in the future.
To recap
NAPA # 655-1022 ---1/4" shaft and bushing for 5/16", approx size as the original Delco in my original GM/Harrison recirculating heater. Cost $33
NAPA # 655-1020 --- 5/16" shaft and a little longer motor than the above, which may fit and is worth a try for the fresh air heater. likely fits a lot of these old heaters if 5/16" shaft size is OK. Cost $27 and is exactly VDO part number PM354 with a NAPA box.
Hope this helps someone else tackle a heater motor swap on a budget and clears up some of the confusion about different more or less suitable motors and what's required.
Grigg
