Sam, as you may have read, I've been doing some experimenting with the W-1 that's on my 216. First it goes without saying that the heat valve has to be completely free. Most of the time the thermostatic spring is shot, they rust out where they slide into the shaft. If you have a new one installed then it probably needs calibration. I was having the percolation problem with mine and did a lot of temperature measurements on the manifold and the carburetor. The problem completely goes away if I wrapped the base of the carb with a wet rag right after shutting down. This told me that the heat was rising up from the manifold after shutdown and heating up the fuel in the foatbowl. The level was set correctly and I even tried lowering it a little but that made no difference. If you ever get a chance to look at a Hudson Hornet you will see heat shields under the dual carb float bowls. Apparently they had percolation problems right from the factory.
http://www.pbase.com/dennygraham/image/116683197 When I installed the new spring (not Genuine GM) it was to tight so I started winding it tighter to relieve the bias on the valve and I now have it where when at cold idle it holds the valve closed but as soon as it starts getting hot the valve will stay open at idle. This seems to have relieved a lot of the hot start problem. Apparently the balance between the counterweight and the bias spring is quite critical.
And yes, a sluggish engine rotation has nothing to do with the fuel mixture, indication of bad connections or weak battery, timing advanced to far, a bad starter, or a tight spot in the engine, in that order.
Denny Graham
Sandwich, IL
