330 GTC exhaust smell in cabin

Perhaps the most common cause in most, including restored (older) cars, is inadequately sealing trunklid or tail gate (and/or its window). More often than not, owners or mechanics mistakenly replace exhaust system. If the mechanic/shop doesn't know (how) to test or is not even aware of this possibility without prompting, I'd highly recommend finding better shop to look after your car(s)...

 

OK.
Next place(s) I'd look into is/are any other rear body openings, including rear window, tail light gaskets or any trunk floor body seams (or corrosion damage), etc...
To best of my knowledge, this phenomenon usually occurs when vent or side window is opened slightly during driving which often creates a vacuum inside the cabin. This vacuum tends to pull in air (and fumes) from aerodynamic "currents/turmoils (?)" created in the "wake" of the moving car.
I have successfully cured this "problem" on variety of, including many "fully restored" (by others), vintage cars over the years by just adequately sealing affected areas in the rear body.
Just because a trunk lid or window seal is new and has appearance of correct style, doesn't necessarily mean it's effective... this seems especially so in vintage Italian vehicle applications.
Hopefully my somewhat unsophisticated "explanation" makes sense.

 

Well said, TTR. Many reproduction seals do not conform to original specs either in dimension or material density. We find this issue with our British and German restorations also. The result is frequently what pgb67 is experiencing. This is why we make many of our own using originals as a pattern.

 

Another approach is to put the car in a dark garage with a bright light under the hood, and look for light penetration into the cabin then under the car etcThere are dozens of little opportunities for seals to fail or to be missing. It requires patience and persistence M

 

I'm not exactly familiar with 330 GTC's Pininfarina coach build methods, but in Scaglietti built 365 GTB/4's and early 250 examples I've studied/tackled with the construction techniques and sealing efforts of the body and floors are often humorous...
I can't tell how many non-Ferrari car guys seen well stripped down Daytona or something similar in my shop and asked "Is that some kind of home-made or kit car ?".
Next "points-of-interest" for me would be various floor openings with boots/grommets/seals/etc, floor sections and body panel seams, etc...

And now with all due respect, may I ask how did you determined the 100% (?) certainty for adequate sealing of all openings ? Spraying copious amounts lightly pressurized clean water (with a garden hose or something) from various angles toward each sealed opening or ...?

 

Timo is correct. There is a non-sealed passageway from under the car through the trunk into the passenger compartment. You have just not found it yet. I have not, personally, ever had a GTC smell of exhaust fumes in the interior.

 

Rear bumper mounts are hollow tubes direct into trunk.
Is that a possibility ?

 

I have always (30 years) had this same problem with my 330GTC. It is not bad but it is there. I will be very interested in hearing the solution to this.

 

It seems like you might be able to find it by using one of those floor drying fans to blow air under the car while you sit inside to see if you can feel or hear any air coming in.

 

Sounds like you already checked it, but in a GTS, so I assume also in a GTC, there are large rubber grommets sealing holes in the bulkhead on the forward end of the trunk. If those are out you get strong exhaust smell.

 

I owned a body shop for 20 years and we checked trunk seal integrity the following way.

Cut some 1" wide by 8" to 12" long strips of heavy gauge paper or similar flexible material. (Something that won't scratch your paint of course)
Close the trunk lid with the strips crossing the rubber seal and into the trunk. You can use low tack tape to hold the strips from moving when you close the trunk lid.
Gently pull on the individual strips and you can gauge how much seal pressure is being exerted. You can sometimes work these strips sideways if the seal is bad.
By using this technique all around the perimeter you can map out your problem areas and diagnose the cause.
You might be surprised to find large areas that really aren't being sealed.
Any low and no seal areas of rain gutter can usually be lightly spooned upwards to increase seal pressure.

 

I had the same problem in a Daytona. Bill @ GT said to look at the foam over the top of the wheel wells. This foam seals between trunk and passenger compartment. I accessed it through the vinyl side panels behind the doors. Pull those off and its kind of a long reach up there. My foam was gone. When I rolled down the windows, that low pressure would pull exhaust through those openings.

Not sure your 330 is the same design in that area, but worth a look.

Bill

 

Here's a winning technique similar to one I've been using over 30 years.

I've always refered mine affectionally as "$1000.00 door/trunk seal test" which not only aids in discovery of poorly sealing areas around the perimeter of many sealed closures as described above, but can also educate and entertain clients if they wish to observe it being performed on their car. I usually start by offering to show the client this special hi-tech (="hi-value") test procedure by requesting them to provide me with 10 $100 bills which I'll be allowed to keep afterwards as compensation regardless of the outcome...
On few occasions clients inquiring if the test could be perfomed with, say $1, $5 or $20 bills, I've pointed out the possibility of such bills not having enough denominational ink to be effectively accurate
Obviously each door or lid opening requires its own set of "$1000 testing equipment" and there's always the required re-adjustment check to be scheduled for a later date...

 

For what it is worth, my 330 GTC has the exhaust smell but my 275 GTB does not. Not something I am worrying about however...

 

When I had my GTC engine rebuilt a few years ago the shop owner-tech showed me how many of the firewall openings were not sealed properly. Some were original to the car while others were "poke-throughs" done by previous owners. The shop properly sealed the necessary openings and close off the others completely.

A couple of pics are on the original thread "My more better GTC" ......about upgrading of certain components to make the car a better driver.

http://www.ferrarichat.com/forum/vintage-thru-365-gtc4-sponsored-vintage-driving-machines/276088-my-more-better-gtc.html

Hope you solve the issue.

 

From the posts, it seems like this is a very common problem on the 330 GTC, but I don't think it is a common issue on the 330 GT. Maybe it is related to the transaxle/linkage?