Calling the Weber gurus out there. I have triple 40 DCOEs on a 2.5L TR6 engine
that is stuffed into my Spit bodied GT-6. Problem: the carbs give off a
noticeable fuel smell after driving the car (when the car is parked in the
garage).
Originally I had these same carbs on the stock 2.0L GT-6 engine and I do not
remember the fuel smell. Back then I kept the car in a detached garage and did
not have a spouse to point out the fuel smell. Since replacing the 2.0 with a
warmed over 2.5L (9.3:1 CR, S2 cam grind, minor head porting, Crane XR700
ignition; currently have about 20,000 miles on the rebuilt engine)I know that
the temps in the engine compartment are a bit higher. I added headers a couple
of years ago and that certainly did not help with the engine compartment heat
issue. I have recently placed a thermocouple between the heat shield and the
underside of the carbs and on the underside surface of the rear most air filter
element. Air / surface temps are typically: ambient+ 50 to 65 deg. F when
stopped in stop and go traffic, ambient+ 65 to 75 deg. F when stopped in stop
and go traffic with the pusher electric fan on and peaking at ambient+ 50 to 65
deg. F after shutting the engine off and letting the engine compartment heat
soak. Very infrequently, the bottom of the air filters show telltale marks
from a slight amount of fuel dampness after the car has been driven. This smell
issue has been an ongoing concern for the past five years. I have done the items
noted below in incremental stages in trying to solve the hot soak fuel smell
issue. THe severity of the smell has been reduced so that the smell is no
longer seeping into the house but still noticeable.
I have done the following to minimize the heat soaking: I have 0.5 in thick
phenolic spacers between the intake and the carbs to minimize heat conduction
from the intake. I have fabricated an AL heat shield that fits under the
intake and carbs. This heat shield starts about 0.75 in forward of the front
carb and extends past the rear carb to within about 0.25 in of the firewall and
extends out to the far edge of the air cleaners. This heat shield is also
insulated on the underside. I have reduced the float height by 3mm below spec.
to reduce the volume of fuel in the carb bowls. There is a press regulator (set
at 1 psi) for the incoming fuel & I have check that the pressure regulator is
functioning correctly. I use a high flow 160 F thermostat. I added an oil
cooler this past summer - addition of the oil cooler had negligible effect on
the water temp but increased my hot idle oil press by about 10 psi. THe engine
shroud on the R/S has been removed to allow heat from the headers to escape into
the R/S wheel well. Two years ago the carbs were dismantled and rebuilt.
Suggestions welcomed.
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