The valve in question is counter weighted and controlled by a bi-metal spring. It's natural state is in the closed position, only opening when the spring heats up from the exhaust heat and starts to coil up, opening the valve in the process. GM engineers installed a counter weight to aid the spring in the opening process and also to act as a fail safe in case the spring broke. What they didn't account for was the valve seizing up, rendering both the spring and weight useless. I checked the valve on the Olds and it wouldn't budge. It was seized solid and I had the sneaking suspicion that it was in the closed position. Unfortunately there is only one way to find out for sure, you have to pull the exhaust crossover pipe down from the manifold. This sounds simple enough but consider that the bolts in the exhaust flanges have probably not been touched in over 40 years! My initial thought was to take the slow approach and muscle the bolts out using a socket and ratchet. As I started to crank on one of the bolts, something just didn't feel right. I got this sick feeling that the bolt was about to twist off and then I would really be up a creek. At this point I figured I had nothing to lose so I abandoned the ratchet and broke out the impact gun. This turned out to be a good decision as it made quick work of removing all the flange bolts - in one piece!
|As you can see the bolt on the right was real close to breaking.|
|A little restriction anyone?|
Armed with my air chisel I crawled under the car to attack the valve. In less then a minute I had the whole thing out. The shaft sheared cleanly on the inside leaving the counter weight intact on the outer piece of the shaft. It was still seized up and the inner edge was bent a little so I wasn't too worried about it falling out. What a piece of cake! I don't know why I didn't think of this in the first place.
|This is what was left of the offending valve.|