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Discussion Starter #1
It stinks of exhaust in the passenger compartment. Stinks when the top is down. Stinks when the top is up.

I’ve read the various threads on this problem. Seems folks point to 2 main causes: 1) Exhaust leak (obvious); 2) trunk lid not sealed well.

I don’t get #2. I assume this is referring to the rubber weatherstrip gasket that enables the trunk lid to seal tightly when it is closed. Why would a poor trunk lid seal cause exhaust fumes to end up in the passenger cabin?

And I was wondering if a more likely cause of fumes in the cabin might be through the cabin air vents.

Thoughts? I’d like to make my Spider not stink.
 

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What is the shape of your tailpipe - curved downward at the end, or a straight pipe?
Chris - always wondered if the curved exhaust pipe was a bit of Alfa spin, but the later ones have a straight pipe.....
I'd say manifold or joint leak - doesn't take much of a leak especially if your bulkhead seals are iffy
 

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if it smells of rotten-eggs, its the catalytic converter. they have a honeycomb center that can get dried up and break up inside and then block the flow. its located right under the driver-seat so it can smell even when the top is down
 

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To be clear, I assume we are talking about your '69 Duetto, so cataclysmic converters and SPICA stuff are right out...

The reason a poorly sealed trunk can cause the stinks, is that the aerodynamics of most cars creates a spiraling updraft just after the trunk, and also creates negative pressure in the cabin. The result is that exhaust gets sucked into the trunk and then pulled into the cabin by the low pressure.

Ever notice that long hair blows up and forward in a convertible? Same principal.

A longer exhaust pipe that aims down prevents this. A short one tipped up creates a problem.

One thing you can do is open your trunk right after driving the car at speed and stick your head in there and smell it.

Second thing to do is check to make sure your fuel tank pressure relief system is working correctly. (Sounds like you've done that already?)

Third, I guess I'd make sure your cabin is sealed tight at the shifter, and that there aren't any holes or leaks in your exhaust system.

Also, are you running rich? Unburned or partially burned gas is stinkier.

**Hey, I see you're in Portland too. You haven't been driving in this weather have you? Because ugh...
 

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...I don’t get #2. I assume this is referring to the rubber weatherstrip gasket that enables the trunk lid to seal tightly when it is closed. Why would a poor trunk lid seal cause exhaust fumes to end up in the passenger cabin?...
Due to aerodynamics there is a draft area at the rear of the car that draws the airflow in, but it is still at a higher pressure than what is inside the trunk so fumes from the tailpipe get in there and then into the cabin through any point that is not sealed. Another aspect however is that if the engine is in perfect tune and at operating temperature there should be very little offensive odor from the exhaust. There is carbon monoxide but that is odorless, what you are smelling is unburnt fuel so the first thing to do is ensure that your ignition and fuel systems are in proper tune. That means points, plugs, rotor, cap, ignition wires and proper tuning of either the Spica system or carburetors.
 

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Ummm. Doesn't a 1969 US model round tail Spider have a 1750 engine with 1st generation SPICA?

To be clear, I assume we are talking about your '69 Duetto, so cataclysmic converters and SPICA stuff are right out....
 

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Ummm. Doesn't a 1969 US model round tail Spider have a 1750 engine with 1st generation SPICA?
Yeah, of course. My bad.

And in fact, my car (SPICA) stunk pretty bad till I cleaned out the fuel tank vapor line that runs along the passenger side of the head. It's a metal line that dives into the head by the thermostat housing. Not sure if '69's have these.

Anyway, my fuel tank fumes were getting pressurized and stinking up the car, until I got that line cleared out. It's not easy to do. I used a length of stiff but bendable 14 gauge unstranded copper wire and solvent.
 

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It's a metal line that dives into the head by the thermostat housing. Not sure if '69's have these.
One of these is in a picture of parts that I am trying to give away for free in the free stuff forum.
 

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Discussion Starter #11
Thanks - yes it is my 69 Spider with SPICA (sorry for the oversight on basic info - doh!).

And, Boccaccia, I am keeping it out of the slop. Was nice enough last weekend though! ;-)

The points on "why do you have the stinky smell in the first place" are spot on and I am working through those one-by-one trying to diagnose. Vapor line is one I hadn't thought of...not positive 69 has one...will have to check.

But the trunk thing puzzled me, hence the question. Makes more sense now - thanks for the detailed explanations.
 

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Have the same issue, tried the new trunkseal and all sorts of exhaust tips but
no luck so far, what Kcab says is coming closer to the truth, my engine is not running perfectly and it is logical I'm smelling the unburnt fuel from that cil. #2 that I can't seem to resolve.

Frans
 
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