Exhaust fumes question for convertible owners

[digithead]

So I got 73 convertible in winter. Now its 70 in NY state so I got a couple rides in. My car has all new headers and dual exhaust all the way to rear tips. Car is running quite nice I'd venture mixture (4BBL) is dialed in pretty close. Starts wells and idles well. But when I drive it theres noticeable exhaust fumes. With or without the roof down. So I thought with roof down, which will be most of my driving on just nice days, I couldnt smell any with the wind. But even at 60 you cant help but to smell it. What do you other convertible owners experience? Is it something I have to live with because its a convertible? I guess they could have messed up exhaust installation, I would need to get it to shop with a lift to go over that. BTW, I do have the fuel evap blue recovery tank thing under hood all hooked up proper, if that has any bearing on it.

 

[luxstang]

Hmmm, I don't have that issue with mine. Neither with the top up nor with the top down.

 

[barnett468]

check ut the entire exhaust system for a leak . even a very tiny pin hle can cause a smell.

look for any open holes in the firewall . plug any holes.

if your exhaust does not go all the way to the bumper it can smell.

if you are using gas with alcohol [ethanol], it can smell like crap.

 

[rocket366]

Check for oil, trans, power steering, and rear axle fluid leaks as

they all smell when leaking ask me how I know.

Paul

 

[Manu Mach1]

Check as well the trunk rubber, I had this problem of exaust smell in the car, but dissapeared after changed this rubber.

 

[piper62j]

The carburetor is running too rich.. Lean the mixture to either the highest idle rpm or highest vacuum reading. If the engine configuration is stock, set the carburetor to the factory specs for best emissions control. Also, having the trunk seal inspected for any leaks will help quite a bit.. Cars are designed to have the exhaust exit the rear bumper so the air flow over the vehicle will pull the fumes away.. Last resort would be to install aftermarket universal catalytic converters, but it's not recommended on older models.

IMHO

 

[Bill73Ragtop]

Never had an issue with exhaust smell with top up or down.

Considering that 90% of the factory exhaust system on 71-73 mustangs had down-turned exhaust tips just barely below the rear valance panel indicates the location of the exhaust tips is not as crucial as a properly sealed system from the engine exhaust manifold to the very end. One thing that might help locate leaks is the sign of exhaust carbon at the slip joints. You can perform initial checks in driveway with car properly jacked up and supported on jack stands.

Charcoal canister system fuel odor issues are most prevalent when parked inside, not while driving.

 

[digithead]

thanks all I have some stuff to check. I think I have a combination of multiple things you all pointed out.

 

[73pony]

Easiest way to check for exhaust leaks under the car. Takes two people. Do not do this after the car has been running a long time, you wan the exhaust to be cool. One person stand behind the car wearing a good pair of mechanics gloves, the other is under the car on a creeper starting at the front and working your way back, there is more room if you put it up on jack stands. Start the car and have the person in the back take their glove covered hands and cover the exhaust tips causing back pressure for short periods of time. If you have leaks they will be easy to spot when you put the back pressure on. If you don't have an H pipe or X pipe you can do this one side at a time but if you do have either one you will need to block off both tailpipes at the same time to create the pressure. When you spot a leak mark it and keep moving on. Then you have all the leaks located and can go about fixing.

 

[digithead]

The carburetor is running too rich.. Lean the mixture to either the highest idle rpm or highest vacuum reading. If the engine configuration is stock, set the carburetor to the factory specs for best emissions control. Also, having the trunk seal inspected for any leaks will help quite a bit.. Cars are designed to have the exhaust exit the rear bumper so the air flow over the vehicle will pull the fumes away.. Last resort would be to install aftermarket universal catalytic converters, but it's not recommended on older models.

IMHO

Thanks, but don't the mixtures you are referring to only deal with mixture at idle? Which would not be the case going down the road at 60mph right?

 

[barnett468]

Catalytic converters will not redirect exhaust gasses, they will only change their chemical properties somewhat and they sometimes change the smell to that of rotten eggs.

 

[piper62j]

Idle mixture is set for optimum combustion at a specified rpm. Many would believe that the idle mixture no longer functions once the throttle plate opens beyond the port, however, that is not the case.. Fuel still enters the throttle body at the idle mixture port at a minimal amount.. It is never perfectly cut off as the throttle is advanced. See the picture..

During the power curve while advancing the throttle, sufficient air intake velocity creates enough vacuum to overide the idle ports and renders them useless.. Fuel is then drawn from the power ports only..

This is why at low speeds, there may be a smell of exhaust indicated by a rich mixture.. The owner in this case has not provided enough details to make an accurate diagnosis, so my first thought was to re-set the idle mixture.. He could have oversized jets for all we know..

 

[cptita]

I just had my carb rebuilt. Ever since I put it back on I've been having the same problem. Last night I took it for a spin and was choking on fumes the whole time. Strong fumes at a stop light or at 50mph. I haven't touched the exhaust, and I thought I had the carb dialed pretty well.

 

[piper62j]

Seems the mixture is way too rich and the fuel is not burning completely..

Float level is very important. Just because the carb was rebuilt, it's very possible the float may be sinking in the bowl or the fuel level was not set correctly...Could have a bent tang on the float lip, or a sticking needle and seat..

Another issue is the jets may not have been seated tight enough on the bowl bottom or worse yet, may have been swapped out for the incorrect size at the time of the rebuild..

There are many factors involved in rebuilding a carburetor (if indeed that is the problem)..

 

[digithead]

my car (original post) has a brand new Edelbrock 650 Carb, FWIW.

 

[Don C]

The 2 Edelbrock carburetors I've tried were rich out of the box.

 

[piper62j]

As you know,, there are a lot of factors affecting a rich mixture.. I've had new aftermarket carbs (Holley for example),, Where I've had to swap jets to get the right combination of power and response.. Just because the carb displacement volume is (say 650cfm), it means the volume of air the venturis will supply.. It does not necessarily equate to a lean or rich mixture.

Let's say you have a mild 1/4 race camshaft installed.. A 650cfm will handle it perfectly due to the volume of fuel and air needed but may require slightly more fuel with larger jets... And remember, the idle is slightly higher than it would be for a stock cam,, Hence, a leaner mixture.. (High idle = high volume of static air intake)

Don't toss a new carb before investing a few short dollars in a jet kit.. In most cases the company who sold the carb can also provide a variety of jets for it, including advice on what works best for your application.

The 2 Edelbrock carburetors I've tried were rich out of the box.

 

[digithead]

So you feel that even going at 60MPH down a straight highway that the idle mixture would be a factor or issue?

 

[piper62j]

So you feel that even going at 60MPH down a straight highway that the idle mixture would be a factor or issue?

Not knowing what you have for an exhaust system, or, how it's exiting the rear of the vehicle, how the carburetor is set up, what the body configuration is on your car, you may be experiencing back draft from the rear of the car.

Think about it.. Ford would not have produced convertibles (or any car for that matter) that would suck the exhaust fumes from the tail pipes, into the passenger compartment.. No one would buy the cars.. Even at 60mph, as you drive thru the air, the flow over and under the car will pull fumes away so you don't get carbon monoxide poisoning.

I've owned one Mustang convert and one Galaxie 500 convert and never got exhaust fumes into the passenger compartment.. this tells me your vehicle has something modified going on..

Unless you're driving with open exhaust manifolds under the hood, with no pipes exiting the rear bumper, there should be no fumes in the passenger compartment.

The exhaust system should be tight and sealed right out to the rear bumper. The guys here will also chime in if they had more information on your car..