Re: 'Blipping' the Throttle

[Glenn Merrell <gmerrel@domain.elided>]

Hello Steven and All,
    Okay, I can't resist this one...

Oil Pressure & engine Oil retention:
    With the engine running, oil pressure is up, oil circulating
throughout the engine. Several quarts are always up in the engine when
running. When the engine is shut down, the oil galleries are full for as
long a period of time as it takes the oil to drain back into the sump.
Depending on the design of the galleries, some will retain oil, some
will drain out, bearings included.  This is why when starting the
engine, it is best not to plant your foot firmly to the floorboard with
the accelerator pedal under it as the bearings are most likely only
holding a thin film of oil from the last shut down, the oil will spin
out before a fresh supply arrives and you will toast your bearings.
When an engine sits for a long period of time, it is best to disconnect
the spark and fuel, crank the engine on the starter until the oil
pressure registers, then connect the spark and fuel to start.

Fuel Priming:
    If your carbs are adjusted properly and the fuel pump is
functioning, the bowls should be 90% full all the time.  Blipping the
throttle and turning off the ignition will put a very rich fuel mixture
into your cylinders, washing the cylinder walls with fuel and removing
any oil that may be there.  On your next start, no oil will be on the
cylinder walls, hence no lubrication for the rings, and increased wear
until oil gets back up onto the cylinder walls from under.  When a
carburated Stag engine is shut down, is is already in a somewhat choked
position with the damper settling onto the venturi as the revs fall off,
forcing a bit of fuel into the intake.  Blipping the throttle on a hot
day just might have something to do with increasing your vapor lock
potential.

The Stag has an electric fuel pump that will pump up the fuel pressure
as soon as the key is tweaked on, filling the bowls.  Fuel should be
immediately ready at the carbs when you pull the choke and tick over.

My opinion is that I would not recommend blipping the throttle at
ignition shutoff, I do not do it on my engines, but I am sure there will
be a wide range of opinions coming your way.

Regards,
Glenn  Merrell

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