Manifold on my 666 is cracked and have to replace it. Just can't seem to wrap my head around how that heat valve works. the old one on the tractor and the new one are hooked up differently. I know that when the valve is open it allows hot exhaust to circulate against the intake to warm the intake while the engine is cold. Is the valve supposed to be spring loaded open and then as is warms the spring closes it and the weight helps it close? The weight on the new manifold wasn't secured to the shaft, so that's part of my confusion. I feel so stupid when something so simple baffles me . Thanks for any help.