The heat riser was frozen on my '57 when I bought it. I didn't want to separate the manifolds for fear of breaking bolts. I followed the following advice that I got from this forum.
I removed the carburetor to get access to the inside of the heater valve. I liberally sprayed Kroil on the inner and outer pivot points every morning and evening and gently tapped the weighted and unweighted ends of the heater valve shaft with a hammer each time I sprayed with Kroil. After a couple days, I grabbed the weighted end of the shaft and tried to turn it. I made progress in very small increments then after about ten days, it magically broke free and has worked fine ever since. I give both sides of the shaft a shot of Kroil for good luck every time I change the oil.
Patience paid off for me doing it this way.
Matt
