 Welcome Back
Congratulations
for making the trip. I'm glad you weren't discouraged by the
introduction and are ready to go with the project. If you are
reading this trying to decide whether or not to try tackling
this project, don't fret. It's not as bad as it appears in print.
Lets begin
Preparation:
Lets
get everything out and ready for our project. There is always
something else you will need, but if you have most of it sitting
around early, it will save you time and frustration. Talking
about frustration, I have always made it a habit to work on some
sort of tarp. If you don't have a good concrete surface to park
on, the next best thing is a tarp. Blue poly tarps are only a
few dollars, and will save you at least five hours if you drop
as many bolts, nuts etc. as I do. Also, you might want to spray
some PB Blaster or other penetrating oil on the manifold nuts
the day before you begin to help the process along. Those nuts
are tough enough without fighting rust and corrosion also.
 Document:
I'm
sure I mentioned a digital camera. If you don't have a digital,
buy one of those inexpensive box cameras and take pictures BEFORE
each stage so you can trace those wires and hoses. Especially
you guys out there with the 78-79 cars with the vacuum hoses
running all over the place. Sure we won't need them anymore,
but if you ever have to put it back on to sell the car or pass
emissions, you will be glad you did. Somehow, I pulled a wire
as I removed the manifold, and the car wouldn't start when I
had it done. This picture showed me where the wire was and it
was a simple job to re-connect it and varoom!
Lets Begin:
First,
lets drain the radiator and block of antifreeze. You will need
a bucket. Just open the drain and let it pour as you do the first
couple of steps. Now is a good time to mention that this stuff
is extremely toxic to toddlers and dogs. Don't leave the stuff
where they can get to it or you might have serious kidney failure.
You need to drain the block in cars with the external thermostat
as the block won't drain. Usually there is a plug or spigot on
the exhaust side in the middle just above the pan.
You start with
a 10mm socket or wrench and remove the air cleaner, snorkel and
the bolts covering the element. Then you remove the four bolts
that hold the housing to the carb. Be careful not to drop the
nuts down the carb throat. It doesn't make much difference now,
but it's good practice for later! take off the cleaner and set
it aside. Next you will take off the linkage and fuel line. You
will loose some fuel here so it's a good time to look around
for anyone smoking or open flames. Grab a 13mm wrench, the smaller
the better and remove the carb nuts, and lift off the carb. The
stock carb can be tricky to get the choke linkage off. You may
have to remove a housing on the carb. Be sure to put it back
on. The guy that buys it from you later on eBay will appreciate
it. Did you take a picture yet?
 Next come all those vacuum hoses and
it's time to get those famous manifold nuts off. You will need
13mm deep swivel socket and a medium extension to get the front
three nuts. depending on your arm length, you might be able to
get some of the rear nut with this combo but you will certainly
be encountering the starter and vacuum booster while you try
to move the nut. I 've had better luck with a small 13mm manifold
wrench. Now I see why they are bent like they are. They must
have had Fiats in mind when they designed them. Usually they
are really tight and it's tough to break them loose. Be careful
and use box end wrenches and be aware of where your hand will
go if you fall off the nut. You could get a nasty gash. There
are a lot of sharp things in a very tight place.
If all goes
well a couple of sharp blows with a wood block should break the
seal and the manifold should begin to slide down the long manifold
studs. You may run out of room on some cars removing the manifold.
It just clears the brake booster on most of them. If you have
a problem, you can raise the motor a bit with a floor jack against
the pan and you should be able to just slide it off. The studs
are angled down about 20 degrees and you will not be able to
wiggle the manifold much. It just comes straight off. As you
can see from the picture (you did take a picture didn't you?)
that there is a lot of stuff under that old manifold that could
use some attention. Get busy and clean up the mess and check
everything. This is a great time to replace all of those gas
lines and clamps. No telling how old they are.
A hand drill
and a wire brush is a good idea here to get all of the old gasket
material and adhesive off the head. This is also a good time
to remove and clean the crankcase breather screen and replace
the hoses.
Removing
the throttle Pedal
If
you have an early model car, you will need to remove the throttle
pedal or grind off the old throttle linkage in place, as it will
interfere with the new manifold. Leave the hand throttle lever
(the one on top, as it is your new throttle cable lever. I bought
a replacement from MIRA so I could keep the original one if I
ever needed it again. Two bolts and you should be able to remove
it. It helps to have an assistant on this part of the project.
 After you are satisfied that everything
is clean and refreshed, you are ready to install the new manifold.
In the above picture, the throttle has been modified and replaced,
the new gasket is hanging on the studs, and I've coated the studs
with a liberal coat of anti-seize compound to try to make this
job easier the next time. I did get in there and clean things
up before I put on the new manifold.
Lets install
the carbs on the manifold before you put them on the car. The
engine side bolts are hard to get to and if you can put the manifold
on with the carbs on it, you are ahead of the game. If not you
will need a 13mm swivel 9pt 1/4" socket and extension to
get the backside nuts on and tight. There is no other way! I
drove all the way to Sears to buy one. Simply slide on the gasket
and slip the manifold up the studs until you get to the head.
On some 2L motors, you will have a conflict with a flange on
the head that will require a little grinding to remove some metal
from the manifold. A mirror is helpful to check out if the underside
of the manifold is making good contact with the head and if there
are any obstructions keeping you from getting it on tight. It
will also help you to feel where those nuts are going to go.
On the emission
equipped cars, there is an exhaust gas passage in the head that
needs to be blocked. You will know if you have one when you remove
the old manifold and find a particularly dirty hole in your manifold
and a matching hole in the head. The stock manifold will cover
this hole. You will need to trial fit your aftermarket manifold
to see if there is a conflict. I've heard that you can tap and
plug this hole or just plug it with JB Weld. I would use the
plug method as it seems a bit more secure. If you are using the
stock Fiat manifold, use the early model gasket as this will
cover the hole. Also some owners plug the water passages in the
stock manifold. You may do so if you want. There is little or
no advantage to this, but some folks do.
 Enough.
Lets get that manifold on. Next come the lockwashers and nuts. This process
is, as they say, "the reverse of the removal procedure"
like yeah right! It's a lot harder getting the manifold on than
pulling it off. Eventually you will get all the nuts on. Be sure
to tighten them down in the proper sequence and a little at a
time. Start on the inside and work on opposite ends progressively
tightening. You don't need a torque wrench here. As tight as
you can get them is probably ok. The back one is going to be
the bad one of course, but you will get it tight after a few
tries. Hang in there. Kick back a bit if you are having problems.
This isn't you daily driver right?
 It's
now time to clean up some more an check out what needs to be
hooked up and what needs to be discarded. Discard everything
except the hose for the oil separator, the hose for the vacuum
booster, and if you have a electronic ignition, the distributor
hose. Be sure that there is a check valve in the brake booster
line. The port is on the front side of the manifold. Connect
it and you are done. The vapor bypass (you disassembled the cast
cover and cleaned it out right?) hose should be led up to the
back of the manifold and left for your air cleaner. The vacuum
line for the distributor must be connected to none of the vacuum
ports on the carbs. The VW 70 series of IDFs have a special vacuum
port that is ideal for the distributor. The 13/15 carbs don't
have an appropriate place to get the vacuum. You can disconnect
the vacuum line from the distributor and just crank in about
five additional degrees of advance to compensate for the lack
of vacuum. While this will not be a perfect solution, it will
get you by until you can locate a single point distributor which
is more ideal for this setup.
Hook up your
fuel lines. You can use a fuel return or not. I've found that
the return line may drain the carbs making the car hard to start
after a period of time, but your installation may not do that.
Be absolutely sure to install a fuel filter inline with the pump.
These carbs are extremely sensitive to dirt in the idle circuits.
Use good quality fuel line and clamps and make your connections
neat and straight. A lot of people will be checking out your
installation. Kris is smiling here, but there his still a lot
of work to be done. The lines need to be run and the linkage
installed before we can drive off into the sunset.
OK it's time
to check your work and make sure that any vacuum ports are plugged
and all the fuel lines are correct and tight. You can't check
this too many times.
It's time to
refill the radiator and get ready to start the car. Have faith.
It will run. If not, remember you have all those pictures. Right?
On most spiders, you have to jack the front of the car up about
three feet to get the radiator high enough to purge the air from
the system. Once the car is full of antifreeze, you can do some
initial settings of the carbs so the car will run when you try.
Before you
try to start the car, GENTLY close all of the small screws at
the base (mounting flange) of the carbs. You will notice that
they are in pairs. one left and right for each of the four barrels.
Open the right one (the one with the spring) about 3/4 turn.
Take the idle screw between the carbs and back it out until it
just contacts the throttle lever. Then turn it in about a turn
and a half. This should get you started. If you have an electric
fuel pump, now is the time to closely check for leaks in the
lines and around the carbs. A sticking float here can cause a
disaster if you are indoors. I like to have a little WD-40 on
hand to start the engine. Just spray it into the carbs while
it is cranking. The engine should start and run rough. Keep it
up until the floats fill with fuel. It's easier on the car than
starting fluid, and is less dangerous if you get a backfire.Spray
some WD into the carbs as you have someone crank the motor. After
a while, it should catch and fire up. Quickly set the idle adjustment
so the engine will idle and then go to the next section of installing
the throttle linkage and tuning the IDFs.
Check for gas
or water leaks. If you have any, you know what to do. Even if
you don't want to. Take pictures!!! Let the engine run for at
least two fan cycles adding water as necessary to top off the
radiator. Put on the cap and lower the car back down to the ground.
You can now adjust those screws with the springs for a smoother
idle. Use your ear for now. Go for the fastest setting and move
the idle back down and go on to the next screw. If you have one
cylinder that doesn't respond, find out why.
You are done.
Pat yourself on the back and kick back and admire your handiwork.
There!!! isn't that nice? Now put all of that stuff away, you've
got to go to work in the morning.
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Fiat Dual Carb installation
