Noel Anderson

How should the exhaust manifold heat riser valve operate on a 1969 350 engine? I notice when my engine is cold the spring holds the weight in the upright position, which I believe is the closed position. When the engine is fully warmed up at idle I notice the weight has only dropped a small bit hardly opening the valve but the valve is loose. Should the valve be fully open at this point, or does it rely on the engine to be revved up to open it all the way? If the valve is bad, how is the best way to remove it?

Thanks,
Noel

joe_padavano

The bimetallic spring should turn the valve almost 90 degrees when hot. If the valve doesn't move this much, it's sticking. That's unfortunately not unusual.

oldcutlass

If you feel it's not opening all the way, you can wire it open. A defective heat riser will damage your engine. When it's time to do exhaust work you can either gut it, weld it open, or replaced it.