bad exhaust smell

[panteramatt]

The exhaust on our 74 dumps right behind the rear tires. My wife smells like exhaust after driving it. Ive tried to figure out how to run it to the rear but doesnt look like theres any room to do so. Anyone have any tips or pics they can share? Also could the carb be too fat? Runs perfect but im wondering if i should lean it out some. It a holley 600.

 

[Broncobowsher]

Behind the rear tires is generally the best place. Sometimes all it takes is an extra inch or two of pipe to get it past the body instead of under it.

Exhaust smell is unburned hydrocarbons. Running a little rich just makes for high CO readings. CO has no smell, just puts you to sleep. So if you have stinky exhaust it is one of three things. Very rich, to the point you are passing raw fuel through. Lean, a lean engine can run good but not sustain the flame front across the piston and leaves raw fuel to go out the tail pipe. Engine is using oil and pumping that into the exhaust will also make it stink. And poor ignition that doesn't light the fuel (poor spark or bad timing) can also cause stinky exhaust.

So while you smell the exhaust, it may not be too rich. It might actually get cleaner if you add more fuel to the engine.

 

[patterdale]

Exhaust should dump out behind rear tire on pass.side. And it should point out to the side. If it points to the rear it is going into an area of low pressure that just drags along behind these little beasts. Also it is good to make sure all holes are sealed in the rear. We have a stock 1970 and have no problems.

 

[73azbronco]

How old is the exhaust? You might have a pipe, flange or header or manifold leak, which then gets into the truck.

 

[panteramatt]

Not sure how old the exhaust is but its in good shape. The rear dumps toward the ground.

 

[WheelHorse]

It will never smell as clean as a new car, the difference was back then, everyone smelled like that.

Fuel inject it and throw some cats at it, no more smell.

 

[panteramatt]

I dont completely believe that. My 69 mach1 doesnt smell at all.

 

[jckkys]

Fuel injection can get stinky too and catalytic converters smell like sulfur when there's a problem. A rich condition is the most likely cause. Other things can also explain it as Broncobowsher said. First check to see if the choke is fully open after warm up. While the air cleaner is off see if the element needs replacement. Check the plugs for soot. Once you know about spark timing, plug reading and carburetion, keeping an engine running well is easier than with EFI.
Exhaust exiting down towards the curb works best.

 

[WheelHorse]

I dont completely believe that. My 69 mach1 doesnt smell at all.

You're dead nuts serious? It's all original with no cats and if you stand behind it, you don't smell like exhaust when you go in the house? If you put your hand up to the pipe you can pull it away, smell it and it smells like nothing?

Who ever tuned this '69 needs to tune your Bronco then.

I've tuned early 70's trucks/cars on the IM240 dyno to where they burned cleaner than mid 80's cars with cats, but you still smelled like exhaust because it wasn't catted.

IF what your saying isn't this; your '69 'Stang has a tighter seal in the cabin than the EB, therefore your clothes don't smell exiting it or after going for a ride, then that's a weatherstripping issue.

Use a flashlight and one person is outside the rig with the light and the other is inside looking for gaps where the light is coming through.

This is about where you want the exhaust to exit to minimize it rolling back into the cabin.

 

[panteramatt]

No my mustangs entire exhaust is brand new and the car is tuned by me. Now the broncos exhaust is at a bad spot but man there isnt much room at all to run it to the rear.

 

[jckkys]

The factory exhaust in my '77 and other late EBs had the exit where WheelHorse's photo illustrates. The hanger on mine is still on the outside of the frame behind the rear shock mount. The tail pipe ran between the spring and fuel tank then turns out in front of the bumper. It did a good job keeping exhaust away, even with the lift gate open. It never got damaged by off road driving.