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Super Moderator
5,640 Posts
Discussion Starter #1 (Edited)
Here is a post that I recently put in the classicopels site, and I thought it might be of interest to this list:

Exhaust or Gas Smell in the Interior?

Have you checked the gas line where it connects to the tank, inside
the rubber cover? Sometimes mud collects in there, and the steel
gas line corrodes. Mine had a couple of pinholes, so small that the
gas wouldn't actually drip but seemed to vapourize, causing a gas
smell inside the car. Or does your tank have a hole in it? A
slight drip of gas into the tail will cause a smell like exhaust.

Or could it be improperly sealed tail-lights? When the GT moves
forward, it creates a low pressure area around the Kamm-tail. If
you are missing the tail light gaskets, or of they are not sealing,
you might draw exhaust fumes into the car. There are also bigger
drain hoses inside the rear compartment from the sides of the rear
window that drain down beside the gas tank. They normally have
rubber ends on them that are "pinched" to prevent road dirt and such
from entering. Are the hoses properly conected to the drain tubes?
If you crack a side window when the car is moving, does the smell
subside? How about if you crack a rear quarter window (on post 1970
GT's)? If you pressurize the cabin by turning the fan on to "high",
does the smell go away?

Or, do you have the PCV hoses correctly installed to the valve cover
and manifold, both the small hose and the big hose ? Blowby gas can
smell like exhaust or gas.

Or, do you have the charcoal cannister (in front of the radiator)
hooked up so that it is vented into the carb throat? Many folks who
install a Weber simply dissconnect the cannister, but then the gas
fumes from the tank have nowhere to go but into the air space under
the hood, and then the fumes work their way into the car.


Super Moderator
5,640 Posts
Discussion Starter #2 (Edited)
What to do With the Cannister Connection With a Weber?

--- In [email protected], Jimsky <[email protected]> wrote:

Just what do people do with this line who have Webers? I think
mine is just hanging out under the hood somewhere by the PO. I'd
like to do something better but never figured out what to do with
this open line. Suggestions?

'73 GT "Katie"


The stock Solex has a fitting around the back, next to the valve
cover, connected to a port in the carb throat just ABOVE the
venturi, which is a fairly low pressure area when the engine is at
cruising RPM. This provides a slight vacuum to allow the charcoal
canister to vent into the combustion process, burning the
accumulated vapours.

Since the Weber has no such port, the next best solution is to
connect to the filter case (if you have the typical chrome box
filter on your Weber) DOWNSTREAM, or inside, the filter, so the
pressure drop caused by the air filter provides the required vacuum
to allow the canister to vent into the carb throat. Many of these
filters have a fitting connection in their base, so I installed a
tee, with one side feeding the big hose to the valve cover (which
DOES flow towards the valve cover, but that is a different topic),
and the other side connected to the canister vent. But if you have
adapted the stock GT filter to a Weber, just connect the canister
vent to the breather fitting just before the carb. Don't worry
about the canister vapours going into the valve cover; at an idle,
they are in turn drawn out by the small hose that is connected to
the PCV orifice at the base of the intake manifold and into the
engine where they are burned. Above an idle, the air flow is
towards the carb throat.

Weber carbs also are missing the float bowl vent connection to the
canister that the Solex has, since it is vented directly to the carb
throat. This was to allow the fumes from the bowl to be accumulated
in the cannister when the engine is at an idle. You just have to
block the extra connection on the canister. Which leaves one
connection from the tank to accumulate tank vapours, and a second
connection to the carb as described above.


Keith Wilford
'71 GT
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