Hi, I have been putting a new exhaust system on my truck... and after pulling off the Y pipe, I noticed there is a buttyerfly valve bult into the passenger side exhaust manifold. It is all spring loaded and very much broken. It still moves, but just spins freely. WHAT THE HECK IS THIS THING??? Its not exhaust or engine breaks is it? My engine is a 318 GAS, and the truck is an 88' Ram 4x4. I have never seen this kind of thing before.... can I just jam it open and forget about it???

 

If it has vacuum to it you are referring to the power heat valve. When vaccum is applied, it closes.

If there is no vacuum it will have a spring and weight assembly and is called a heat riser valve.

http://autorepair.about.com/library/.../bldef-301.htm