"Percolating" is when the fuel in the float bowl boils causing
pressure wave changes that can make the float needle to cycle. This
may cause the bowl to overfill allowing excess fuel to be drawn into
the venturi. A condition that usually only occurs in desert type
heat or poor racing designs. An aluminum spacer and/or carb
baseplate heat shield should solve the problem. Excessive fuel
pressure will cause bowl overfill. An inline regulator at the carb
set at 6psi is required. Overheated fuel lines first cause fuel
pressure increase, then "vapor lock", where fuel is vaporized before
it gets to the float bowl. Wrapping and/or rerouting fuel lines is
the cure. Obviously, both conditions go away once the system cools
down. Very low manifold vacuum at idle (for whatever reason) can
cause power valves to prematurely open adding excess fuel delivery.
Dirt in the needle seat, power valve or main air bleed(s) can cause
the same effect. A good fuel filter is a must. A remote possibility
would be that the float has a pinhole leak keeping the needle from
seating. If the car refuses to start, the spark plugs are probably
soaked and will require removal/cleaning. This much raw fuel will
bleed down around the rings, diluting the oil and necessitating a
change. Keeping fuel very cool is for wide open throttle performance
with the caveat of reduced part throttle driveability and economy.
Happy hunting,
GM
-----Original Message-----
>
>Does anyone have experience with this "percolating" situation and
know
>if that fix is correct or is there some adjustment that needs to be
made
>to the Holley?
>
>TIA...
>
>William (Bill) H. Whitney, Bricklin VIN #624
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