GATOR454

My exhaust pipes were flattened on the bottoms near the oil pan (which also looked like it went through H**L ). The cross section of the pipes on both sides was only about 60% of what it should be, so I decided to replace it.

When I was removing the pipes from the manifold on the passenger side a valve assembly dropped off of the flange. What is this valve's purpose? Why isn't there one on the drivers side? When I put in the new exhaust does it need to go back in? If I decide to get headers does it need to go back in? What does it change if it's not there?

Crash80

Sounds like you have found the infamous heat riser. It is there to help the engine warm up faster for better driveability in cold weather. Lots of guys have removed them with no problem. Mine is still on my car, an '80 model, and has given me tons of grief with exhaust leaks and what not. Mine will go when I re-do exhaust on mine. I have heard from many that they tend to stick closed as they get older and wear out. I hope that answers your question.

CVT4ME

68shark

Yes, definitely a heat riser as CVT4ME says. Mine is "gutted" thus it's basically just a spacer with no valve in place. Will increase warm up slightly but no big deal. You can certainly buy new ones from Eckler's and probably GM, but I wouldn't bother with it. It works by diverting exhaust gas by blocking the pass. side pipe through the crossover in the manifold such that the exhaust all exits out the drivers side pipe. This quickly warms the intake manifold, reducing the time that the choke operates. As the car warms up, the valve opens up eventually to a fully open position, allowing exhaust out the pass. side as well. Even when open though, it's an obstruction you don't need. After all, it's rare to find one of these as "daily drivers" including full northern winter use.