My '67 Cutlass is a blast to drive, but my dual exhaust gets into the passenger compartment when I open the windows. My exhaust is new, and it's really tight, so I don't think it's a leak; however, my exhaust tips are probably too short (see photo). I'm guessing there's a vacuum created at the back of the car, and the tips need to be long enough to get past this? When my windows are closed, it's not a problem.

Does anyone else have this issue? Should I lengthen the exhaust tips? If so, how much? Also, any luck with tips that point downward?



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I don't think it's the tip length, those look about right. It's something else like maybe a bad trunk gasket, missing floor or quarter plugs, rust holes in floor or trunk...I don't know. New exhaust always smells for a while, it goes away. If it continues, you got to find it! It's neither healthy nor safe for you.

 

My exhaust turns down behind the bumper and I don't have any issues. X2 on the trunk gasket or other contributing factor.

 

That exhaust is the normal length. There's something else wrong.

- Eric

 

x2

 

Thanks for the replies! When you say trunk gasket, is that the gasket that seals the top trunk lid?

 

Right...the gasket that seals the lid. It could be tailight gaskets, rr qtr gaskets...I don't know, but it's not normal at all. It's not vacuum....

 

 

If I drive with the windows up (sealed), I don't smell anything. It only happens when I run with my windows open.

I suppose my front air vents are keeping a positive pressure on the cabin, then when I open the windows, it's circulating air from the trunk area. It's a convertible, so there's not much separating the trunk from the passenger cabin. That's why I was thinking it was a vacuum (vortex) thing from the backside of the vehicle.

I'm going to work on that trunk lid seal (first thing).

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Looks like it rides on the drvrs side rubber bumper, so drvrs side might be adj to low and the pass side might not make complete contact w the gasket. Can you see where the gasket has and hasn't been compressed? Are the tail light gaskets present and in good shape ?

 

Not sure about the tail light gaskets, but I'll look this evening.

I tried to look for gaps using a sheet of paper, closing the lid on the paper at several spots, but that method was hit or miss. I think I'm going to paint something temporary on the rubber, shut the lid and see where it leaves a mark on the lid. I'll dig around my daughter's art supplies and find something that works.
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Ok...trunk gasket doesn't look too bad, it might be the profile or height of the rubber, but looking at it...it looks ok. I see something...do you have a well liner in there? I don't see it.

 

How new is your exhaust?
As previously noted, they will stink for a few hundred miles until all of oils burn off.
You said that when Window closed and Fans on, you do not get the smell.

I had a similar problem with a borrowed 1973 Chevy Blazer.
The owner changed bucket seats and had to drill new holes for the seats. He never plugged up the old holes.
When the windows were open (no AC), the holes in the floor sucked in the gasses from a Leaking Exhaust system.
With windows closed and Fans on, no smell. Open the windows and lots of bad gases.

If we assume your car has NO rust holes, I would suggest you check for any type of body holes,
including: Firewall, Unsealed Cable holes, Door seals, Pryor body modifications, all trunk feed through, etc.

As for the Gaskets:
Try the Chalk Test.
Rub chalk on a section of gasket, then closed the lid and reopen.
Then look on the opposite side for a chalk mark.
If you do not see any chalk transfer, then you may have a gap in that area.



As a temporary Fix, you can Try to add another 3-6” tail pipe extenders.
I drove my 71 CS convertible for 10 years and never noticed any exhaust issues.

 

Yes look for holes of any type in lower quarters or trunk. Also make sure your engine is not running too rich or burning something it should not be burning like oil or antifreeze that would make your exhaust extra smelly.

 

Great ideas, thanks! I'll be under my car this weekend looking for holes