That depends if it's stuck open or stuck closed,stuck open and in cold weather the engine will not come up to temp and the heater will blow luke warm air at best.
Stuck closed the engine will overheat and and the heater will blow cold air because there is no flow to the heatercore.

 

its going to be hard to tell the condition of the head/head gasket until it is removed from the engine

 

A compression test will tell which cylinders are leaking,usually the gasket blows between cylinders and you will get a low reading from two cylinders next to each other.
As for the head,yeah it will have to be off the motor.

 

Ok, well thanks for all your help, but I think my transmission blew up.... lol 170+k it was only a matter of time.. Alih, if you come up to washington ill still let you hit it with a stick[8D]

 

sweet

 

yeah, its always been difficult to get into drive and when it did finally decide to go into gear after all the delay it would hit hard, then it would only skip in high rpms and from 1st to 2nd. Well my timing is off so going up hill usually requires me to pretty much floor it to maintain any amount of forward motion. Well i was doin about 35mph up this hill at nearly 5000 rpms and when i got to the top i let off and the tranny just slammed. I pulled up to the red light and when i tried to go it felt like it didnt want to accelerate and finally i got it up to 50mph before it shifted and each shift was delayed and hard. That was earlier today and i havent driven it since. SO i guess it was good while it lasted. No major problems until the snow hit other than the delayed/hard shift from Park to Drive and the skipping tranny from time to time.. Butall the snow is gone now so i wont be sitting on the side of the road in the snow. Just the cold and the rain.