I have a 1970 Chevy pick-up, C-10, with a 350 V8. The heat riser valve on the left exhaust manifold is sticking. My question is: what position should the counterweight on the heat riser shaft be to have the valve open, so that the exhaust can flow into both pipes? I am thinking that when the counterweight is down, the valve will be open, because the pipes are hot and no exhaust crossover is needed. Have I got this right? Thanks, Irmajoan.