dreaded exhaust in the car

[Ron Dame]

I'm getting exhaust in the cabin, so lets start with the basics. This is Thea, a 1980 Avanti II. It has a nearly new stainless steel exhaust installed by Jon Myer before I bought the car from him. I can't hear any leaks, but my ears suck.  The trunk seal looks OK, not pristine, but not badly cracked and no serious cracks or lost chunks. It seems to close correctly and fully. The exhaust tips extend past the lower valence as they should. If the windows are all closed and the vents open, no problem.  I'm not sure about if the vents are closed. Windows down, all is OK, but some smell enters the cabin with either with any of the other glasses open or shut. If the windows are up and either the vent wings or rear vents glasses are open, I get exhaust inside.

Where do I start looking for this?

[64studeavanti]

Check under the rear seat. Studebaker Avanti's had a hole in the floor. Later ones may have one as well. Don't know why, so I just seal it with some hvac tape.

[Ron Dame]

Thanks!

[Mel]

I had the same problem.  If you have access to the older issues, specifically Issue 175 (Summer/Fall 2016, pg. 35), I wrote up my experience.  Succinctly, I had a hole in the passenger exhaust manifold which, I think, was original and, I also think, machined to accept a stovepipe which led up to the (engine heated) automatic choke.  Mine is a '66 and carbureted but now has a different choke mechanism; I don't know if yours is similarly equipped.

The hole is on the inner side of the manifold and goes up through the exhaust pipe mounting flange into the heat riser mechanism.  I started a 5/16-18 regular tap and finished with a 5/16-18 bottoming tap and made about 6 complete threads.  Both Noise and exhaust smell significantly reduced.

Good luck.

[brad]

I made the mistake of putting local parts store exhaust extensions on an Avanti once. Instead of fitting the pipe, it was slotted to be a universal fit, and exhaust fumes leaked out the slots, and since that was not past the body, that was where the fumes came from. 

[Lamacchina]

One of the best tools I ever bought was an exhaust smoke machine.  I've used it on all of my cars to check for exhaust leaks.  With the engine off, it forces smoke into the tailpipe and shows the leaks.   It makes the driving experience better by not smelling like exhaust when I get home.  The one I have is "Autoline Pro", costing a little over $100.  https://www.amazon.com/AutoLine-Pro-Automotive-Detector-Diagnostic/dp/B07JVT1NG2  I then disassemble any leaking joints and use an exhaust assembly paste, i.e. Hylomar EAP5.