Holley Rebuild
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Other Holley info after
the rebuild section
Holley
3310-2 / 780 CFM Rebuild
OEM 780 CFM List 4555
GM Carb Stud - total length is 1 7/8"
Believe it or not, I needed to run 5/16-18 NC
die on the ones I bought since they were too tight to screw into the intake.
The 5/16-24 NF was cut correct.
The 3310 below is my spare carb. At the time my 780 cfm did not require a rebuild, so I
just used my spare to take apart and snap shots.
The principle is the same
except there is no rear metering block on a 3310-2 750 cfm Holley.
I will add 780 pics when I need to tear down my 780
for problem resolutions.
780
3310
remove 4 fuel bowl mounting screws. If your going to just swap jets or change
gaskets while the
carb is still on the car, then remove one of the lower
bolts 1st and drain the fuel into a funnel/container.
Front Bowl/Metering Block
pry front metering block &
remove gasket and remember orientation for new one
780 front metering front block/bowl/baffle
Remove power valve
views using a 1" socket (780)
Now test the power valve for leaks.
Place a spark plug boot tight against the front and suck the air out and
using your tongue see if it stays closed. If it holds, then it's still good.
Clean gasket surfaces and clean all holes/passages
with carb cleaner and blow passages out with compressed air, then install power
valve.
Place in a vise with wood on each side
of the vise jaws so you don't damage it and
using a 1" socket install/torque.
Note gasket type.
When installing, tighten
to the following specs. For
power valve with multiple drilled fuel opening, torque to 40-50 inch pounds.
For power valve with 2 rectangular fuel openings, torque to 100 inch pounds.
3310 front metering block -
note gasket orientation pins
jet side
metering valve side
Rear Bowl/Metering Block (no metering block on a 3310-2)
Remove 780 rear bowl, clean parts, and remove power valve, then reinstall
power valve
Remove front idle mixture screws, 2 per front metering block, and change cork
gaskets. You can use a 7/32" drill bit to push it all the way in.
Install screw all the way in clockwise until it lightly
touches the end (don't over do it or the point will get damaged.
Turn both screws out 1.5 turns counter clockwise for initial
startup.
Jets
There are 2 per metering block front/rear (none on the rear of a stock 3310-2)
Using a thick straight screwdriver, remove both jets, there are no gaskets here.
Front 780 jets are 70 and rear are 76.
Needle and Seat
Using a wide screwdriver, unscrew and remove the lock screw.
Then turn the nut counter CW to remove the needle/seat (.110)
Note paper
gasket on both sides of the nut.
Needle/seat removed. Replace them unless they are fairly new. Before you install
them, take compressed air and blow them clean while
holding the needle off the seat. One spec of dirt will cause
flooding.
Before installing the needle/seat, lube the needle/seat O ring with a dab of oil or the
O ring will be too tight on assembly and may tear
turn bowl upside down and turn the needle/seat clockwise until the bowl is
level, you'll check this later with the car running
Check to see if the float is getting any fuel inside. Remove
it and shake it.
Using
a flat screwdriver remove the float.
Remove the from and rear (780) fuel level site screws and note a metal gasket.
Some kits today are using a
plastic washer. I myself use the metal ones, because
I don't trust the plastic since it
doesn't compress.
Front accelerator pump
Using a square head screwdriver, remove the pump cover and
note diaphragm orientation and spring.
If the gasket is old, it'll be hard and won't be able to flex
so replace it.
Secondary Vacuum
Side view of secondary vacuum linkage/manual choke if equipped as on the 3310
3310 - Remove side choke mount and note paper gaskets and
replace from kit
Note the cork gasket, if this isn't installed then the secondaries will not open
& you will have a vacuum leak
Remove secondary vacuum diaphragm housing. Note
spring orientation, it snaps into the post.
Check the chart below for correct
spring color (plain color are used from speed shop carbs)
Also
note chrome ball will be here on 71+ Holley's
Fuel Filter
Remove fuel inlet fitting, note metal gasket. If your using the stock fuel
filter then it'll be the hard brass ones.
Don't forget the spring if your using this
location. If you don't want to wear the fuel line attachment bolts
even when using a
fuel line flare wrench then install an inline fuel filter.
Body -
using a wire (guitar string) clean out these holes
3310 Rear
Remove rear fuel bowl
The 3310-2 has no metering block but a plate to keep costs down, remove plate
using a square screwdriver and lift and remove gasket.
For the 780 remove the bowl/metering block the same as you
did for the front.
With the bowls off and metering blocks or rear plate, remove all philips screws from the throttle body
and note gasket orientation
780 rear bowl/float/metering block
This screw is your secondary stop screw and must be set off the car, see Step 2
below after the rebuild section.
Remove nozzle pump screw and 2 paper gasket
Then remove the needle
Pump discharge needle
orientation (paper gasket on each side of the pump nozzle)
Clean all parts with carb cleaner and assemble in reverse order and setup
While WOT is held open, using a flat screwdriver, push the lever down and take a
reading, it should be .015, if you don't do this you will have a stumble when
you press the accelerator
If while idling you give it some gas and it has a stumble and
the .015 doesn't fix it then you need to test the power valves. My rear one was
shot when this happened in July 2011.
turn in lightly until they stop, turn out 1.5 turns. When car is idling, set
until you get the highest RPM or
highest vacuum reading with a vacuum gauge,
then do the other side then repeat the drivers side.
Remove while idling and the gas should be at the bottom of the threads. If you
nudge the fender with your leg, it should just trickle out.
If gas is coming out too fast, reinstall site screw
and lower float
With car running, using a box wrench, hold nut so it doesn't turn, then loosen
lock screw just enough so you can turn
the NUT 1/4 turn clockwise (this nut
is connected to the needle/seat and lowers it or it can raise it to raise the
fuel level in the bowl).
Rev the throttle once and wait 5 sec.
Open fuel bowl site screw and check the level. If it's still too high, repeat
procedure. If the fuel level is too low,
then the nut needs to be turned
counterclockwise to raise the needle/seat thus raising the float.
Fuel Line Bracket
Rear
fuel line support bracket
Fuel Filter
I use a 3/8 inline filter hidden under the
alternator bracket.
GM GF61P part # 854619 
3310--->
780--->
<--- 780-->
780--->
780--->
