A
Anonymous
Guest
If you are so fortunate (?) as to own the 1946 Holley,
you may be experiencing it's most common problems:
- Rich mixture that can't be controlled.
- Erratic idle after it warms up.
- Extra-long choke 'on' time, even if electric.
After my 7 years and 12 rebuilds with one, here's my bag of
tested tricks:
1. If the carb has 40k+ miles on it, go get a 12-24 Helicoil
set with drill. You'll need up to 7 inserts with the kit.
Get 7 screws, 12-24 "cheesehead" type, 2" long and
fully threaded. These can be easily trimmed to length:
mostly they will be 1.625"-1.75" installed length.
2. Get a GOOD rebuild kit: you know where NOT to go.
Rule of thumb: if it costs less than $15, it's not good.
The gasket material is very important in this carb, more
important than for most carbs.
3. This carb has some 'features' you should know about:
a. There is a "hot idle compensator" under a small .5"x1"
cover on the side of the body. There is a spring-looking
device inside with a small gasket behind part of it: The
flat side of the "spring" goes toward the carb. A small
gasket, be it cork or rubber, goes behind the "spring",
over a hole. This makes the device seal and work
properly. They are often mis-assembled. There is another
gasket under the cover over this device: this is often
missing if a PO rebuilt it incorrectly. This device is
the source of hot-idle problems when it leaks air.
b. In the center of the carb (top removed) is the power
valve. These are spring-loaded open, feeding gas, until
high engine manifold vacuum pulls them shut. Around the
top of this plunger-looking device is a small vacuum
passage that goes down to the manifold side of the
throttle plate. This is how vacuum gets to the valve
and is the trouble spot on most 1946 carbs, leaking the
vacuum along the way. This causes rich mixture through
the whole RPM range, because the valve won't close.
c. Upon reassembly, snug the center screw first, then work
from the rear to the front, snugging in a pattern back
and forth across the carb. Repeat the process for the
final tightening. This seals the vacuum passage best
and reduces the chance for gas leaks.
d. The choke coil gets its heat from a coil of tubing in
the exhaust manifold. Chances are, this tubing is gone
now, corroded away (more about this later). There is a
small passage in the top right corner of the choke
housing that goes down to the manifold vacuum port at
the throttle plate. This port pulls the heated air
through the carb to 'start' the electric choke (more
about this later). This port is probably plugged and
needs to be cleaned with the help of a small wire.
4. DON'T use any sort of gasket sealer when rebuilding it.
It will not withstand the vacuum stresses and will end
up missing, causing leaks again.
METHOD:
First, check for stripped screws - the big ones that hold
the top & bottom onto the body. Many are stripped, which is
where your 12-24 Helicoil kit comes into play. Second,
clean/soak/re-clean that throttle body very thoroughly:
take your time here. Follow and clean EVERY passage, using
small wires as needed. You'll see how it all works if you
study it for a few minutes.
The float setting is described in the sheet that comes
with the rebuild kit. Do this carefully, as being off just
1/32" will make a large difference in engine running
quality. This is one of 2 fuel calibration adjustments in
this carb (the other is the main jet).
After reassembly, set the air screw at 2.5 turns out from
bottom for startup. This will get you close.
Let the carb sit overnight, then tighten the screws again,
top and bottom sides. You'll find them to be somewhat loose.
After that first tank of gas has gone through the carb,
tighten those screws once more. This will extend the life.
Electric Chokes:
These must be heated to 50 degrees before the electric part
'kicks in' to heat and open the choke plate. Below 50
degrees, the heat comes from the exhaust manifold. The
whole circuit starts at the "air horn" of the carb where
there's a tube for 1/4" rubber hose. This hose goes down to
a metal tube that enters the exhaust manifold. There was,
when new, a coil of tubing inside the exhaust manifold that
exited into another metal tube that went back up to the
choke housing on the carb. The vacuum passage then pulled
this warm air past the electric heater to warm it past 50
degrees. Then the 7 volt AC power from the alternator can
pass into the electric heater and open it up. Exhaust has
probably eaten away your coil inside the manifold, so wrap
about 3 or 4 turns of soft 1/4" copper tubing around the
outside of the manifold, connecting one end to the choke
housing and the other to the tube on the carb's 'air horn'.
Drop me a PM if you have more questions, and I'll try to help.
you may be experiencing it's most common problems:
- Rich mixture that can't be controlled.
- Erratic idle after it warms up.
- Extra-long choke 'on' time, even if electric.
After my 7 years and 12 rebuilds with one, here's my bag of
tested tricks:
1. If the carb has 40k+ miles on it, go get a 12-24 Helicoil
set with drill. You'll need up to 7 inserts with the kit.
Get 7 screws, 12-24 "cheesehead" type, 2" long and
fully threaded. These can be easily trimmed to length:
mostly they will be 1.625"-1.75" installed length.
2. Get a GOOD rebuild kit: you know where NOT to go.
Rule of thumb: if it costs less than $15, it's not good.
The gasket material is very important in this carb, more
important than for most carbs.
3. This carb has some 'features' you should know about:
a. There is a "hot idle compensator" under a small .5"x1"
cover on the side of the body. There is a spring-looking
device inside with a small gasket behind part of it: The
flat side of the "spring" goes toward the carb. A small
gasket, be it cork or rubber, goes behind the "spring",
over a hole. This makes the device seal and work
properly. They are often mis-assembled. There is another
gasket under the cover over this device: this is often
missing if a PO rebuilt it incorrectly. This device is
the source of hot-idle problems when it leaks air.
b. In the center of the carb (top removed) is the power
valve. These are spring-loaded open, feeding gas, until
high engine manifold vacuum pulls them shut. Around the
top of this plunger-looking device is a small vacuum
passage that goes down to the manifold side of the
throttle plate. This is how vacuum gets to the valve
and is the trouble spot on most 1946 carbs, leaking the
vacuum along the way. This causes rich mixture through
the whole RPM range, because the valve won't close.
c. Upon reassembly, snug the center screw first, then work
from the rear to the front, snugging in a pattern back
and forth across the carb. Repeat the process for the
final tightening. This seals the vacuum passage best
and reduces the chance for gas leaks.
d. The choke coil gets its heat from a coil of tubing in
the exhaust manifold. Chances are, this tubing is gone
now, corroded away (more about this later). There is a
small passage in the top right corner of the choke
housing that goes down to the manifold vacuum port at
the throttle plate. This port pulls the heated air
through the carb to 'start' the electric choke (more
about this later). This port is probably plugged and
needs to be cleaned with the help of a small wire.
4. DON'T use any sort of gasket sealer when rebuilding it.
It will not withstand the vacuum stresses and will end
up missing, causing leaks again.
METHOD:
First, check for stripped screws - the big ones that hold
the top & bottom onto the body. Many are stripped, which is
where your 12-24 Helicoil kit comes into play. Second,
clean/soak/re-clean that throttle body very thoroughly:
take your time here. Follow and clean EVERY passage, using
small wires as needed. You'll see how it all works if you
study it for a few minutes.
The float setting is described in the sheet that comes
with the rebuild kit. Do this carefully, as being off just
1/32" will make a large difference in engine running
quality. This is one of 2 fuel calibration adjustments in
this carb (the other is the main jet).
After reassembly, set the air screw at 2.5 turns out from
bottom for startup. This will get you close.
Let the carb sit overnight, then tighten the screws again,
top and bottom sides. You'll find them to be somewhat loose.
After that first tank of gas has gone through the carb,
tighten those screws once more. This will extend the life.
Electric Chokes:
These must be heated to 50 degrees before the electric part
'kicks in' to heat and open the choke plate. Below 50
degrees, the heat comes from the exhaust manifold. The
whole circuit starts at the "air horn" of the carb where
there's a tube for 1/4" rubber hose. This hose goes down to
a metal tube that enters the exhaust manifold. There was,
when new, a coil of tubing inside the exhaust manifold that
exited into another metal tube that went back up to the
choke housing on the carb. The vacuum passage then pulled
this warm air past the electric heater to warm it past 50
degrees. Then the 7 volt AC power from the alternator can
pass into the electric heater and open it up. Exhaust has
probably eaten away your coil inside the manifold, so wrap
about 3 or 4 turns of soft 1/4" copper tubing around the
outside of the manifold, connecting one end to the choke
housing and the other to the tube on the carb's 'air horn'.
Drop me a PM if you have more questions, and I'll try to help.
