I was browsing the service manual today and found the blurb about "Winding up" the spring.
"The tension of the thermostatic spring is very important. When too tight, the heat will not be turned off the intake heat riser as the engine warms up, with the result that the incoming gasses will be expanded several times greater than normal and it will be impossible to get a normal fuel charge into the cylinders. ....... Therefore, is is important that the thermostatic spring be wound up just enough to slip its outer end over the anchor pin (fig. 4) and no more. This is approximately 1/2 turn of the spring from it's position when unhooked."
BTW it looks like you had it the right way, but just didn't have it "wound up" enough. It's not supposed to be wrapped around the anchor pin.
Kevin, I noted that with the heat control valve closed it takes about 1/2 a turn of the spring to get it over the anchor pin. I'd also read that section and everything seemed to be correct as far as how I installed it. Once I get the heater core replaced I'll give it a real test with the engine running and see if it works properly. Thanks again to everyone who responded with advice and suggestions.
