Just behind the O2 sensor, there is a pipe that leads up to the engine area that I assume is the heat riser?? That part corroded off and a friend mig welded the leak, but the pipe is hanging loose. My concern is what effects having this pipe not connected.
Thanks Rick
This is not a heat riser. The smog pump pumps air into two places. One place in into the head near the exhaust ports. The other is the one you speak of, after the O2 sensor and before the cat. The only thing that will be wrong with the pipe being open is that you may hear air escaping from it when the smog pump is running.
So rather than saying you have a problem you could say that you have the problem half solved. If you plug the port on the head you have eliminated the smog pump system. Then you can remove all the lines that come off the smog pump.
Adrian Holt
The heat-riser consists of a duct/shroud that covers the front part of the exhaust manifold. It uses a flexible aluminum tube that connects the metal duct to the bottom of the air cleaner. This little duct/tubing system is what brings heated air into the bottom of the air cleaner. There is a vacuum actuated valve in the body of the air cleaner that opens/closes that heated air into the air cleaner system. That is the heat-riser valve.
Dave S(Texas)
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