Mystery: Exhaust fumes pretty bad

[Scoopy G]

Hello again,

As I finally got my '65 New Yorker 6-window Town Sedan back on the road last week, a curious thing happened.

All was fine for the first 100 miles of city and highway driving, working the bugs out. Then I noticed the exhaust tips on both sides terminated underneath the car. I figured that can't be good, so I got some pipes and extended the tips to go past the rear bumper, see photo. I didn't notice any exhaust smell before I extended the tips, but I figured it made sense to get the tips out past the bumper.

THEN, all was good yesterday when I set out early to see a car show. BUT, when I rolled down my window, the exhaust fumes came in and were pretty strong. With the window rolled up, no fumes. Crack the wing window....fumes.

What's going on?

 

[EurekaSevven]

Only things that would come to my mind are an exhaust leak or a broken/cracked pipe somewhere down the line for each exhaust pipe. It could also be that you're burning oil, my 383 has that issue (really needs to be torn apart and freshened up). It's something akin to a burnt foliage smell. But if you're not smelling oil and it's just gas fumes I would say it's broken pipe or exhaust leak, because nothing else should be reeking of gas when you open the drivers side window.

 

[Scoopy G]

Thanks Eureka,

It isn't a gas smell, it's clearly exhaust fumes. But now that you mentioned it, today I had a gallon can of gas in the trunk, and as we were cruising along, all was just fine. But when I opened the window, I could smell the exhaust fumes AND the smell of gasoline.

 

[Xenon]

When you are driving at any recordable speed and windows are up there is
positive air pressure in cabin... When you open any window it allows air to
be sucked out creating a negative pressure in the cabin...
Now couple that to more than likely the trunk seal is old and worn and allows
fumes into the trunk which get sucked into cabin thru rear seat.. This would
explain both the exhaust fumes and the raw gas smell from the trunk....
You could try turning on the blower fan on high but even that will not be enough
positive pressure to compensate for the amount of air the window allows out...

Would also be a major help if the tail pipes had a turn down (towards ground)..

 

[Scoopy G]

Thanks Xenon. I knew that a car in motion creates a certain vacuum, so I suspected that with the windows down, air was being sucked in from somewhere.

I did some investigating tonight and found that there is a valence in the rear-most area of the trunk, above the rear bumper if you will. In that valence there are a series of 2" holes to access the bulbs. Those holes are (or should be) sealed with plastic plugs. If they are not, then there is basically an open path from the tailpipe into the trunk.

I had a number of loose extra plugs that came with the car, but just then realized where they they belonged. I got them installed as you can see in the photos, so we'll see if this solves the problem.

Thanks for the help everyone, I appreciate it.

 

[Timmayy]

That would do it.

 

[live4theking]

I would imagine that a '65 would also have the floor vents in the kick panels too, right? If you open the passenger side one a little bit while you have your drivers window open it will cause some cross ventilation too.