~ Removal/Installation Procedure and Discussion. ~
(For dual-port engines)
See also our discussion of the Heat Riser Flange connections to the muffler, and cracking of the intake manifold that can result from too much stress.
Intake Manifold Removal Procedure -
the engine in the car, you must partially remove the fan housing
before you can completely remove the intake manifold, or before
you can remove the alternator. However, it you are only removing
the manifold end pieces, you do not need to remove or partially
remove the fan housing. Steps in this procedure shown in
red do not need to be performed if you are only removing
the end pieces.
Remove the drive belt as follows -
front half of the alternator pulley has two cut-out slots in
it. Inserting a thin screw driver in either slot locks the pulley
so you can loosen/tighten the 19mm retaining nut. Remove the
retaining nut on the alternator shaft with the 19mm wrench,
then slip off the washer, any spare shims, and the outer pulley
half. Take note of how many shims are between the pulley halves
so you can easily re-tension the pulley on reassembly.
the belt off the crankshaft pulley and remove it.
the inner pulley half, being careful to remove the Woodruff
key and stow it and the shims and nut in a baggie in a safe
the air cleaner.
the accelerator cable from the throttle lever and remove the fuel
line from the fuel pump to the carburetor.
- Disconnect the incoming fuel line to the fuel pump and plug it.
the fuel pump, as it will be in the way later when you need to
secure the manifold tongue to the engine case.
out the accelerator cable guide tube and pull the accelerator
cable forward, out of the fan housing.
the cable from the negative terminal of the battery.
and then detach the electrical connectors from the alternator.
the wire to the backup lights at the in-line fuse.
the strap that holds the alternator to the support.
the ignition cable from the coil and the fresh air tubes on either
side of the fan housing. Disconnect the spark plug wires from
the attachments in the fan housing (three places).
the engine lid and the engine lid hinge brackets. You must remove the brackets
to get enough clearance to lift the fan shroud.
the left side of the car, reach down in front (front) of the fan
housing with a 10mm box-end wrench (ring spanner) and remove the
bolt for the oil cooler cover and the bolt that holds the fan
housing to the oil cooler flange. This is awkward and you'll be
working largely by feel.
If these two connectors are cheese-head screws, replace them with
10-mm hex-head bolts. This will save you lots of trouble reinstalling
them and removing them next time (10-mm open-end wrench (ring
spanner) instead of an offset screwdriver.
the oil cooler cover and the air duct.
the thermostat and unscrew the thermostat from its rod.
and remove the connecting link between the cooling flaps in front
of the fan housing (don't lose the spring).
the two bolts on either side of the fan housing. The one on the
left also supports the metal fuel line, and you may need to disconnect
this line from the fuel pump to move it out of the way.
the fan housing enough so you can remove the four mounting bolts
from the outer fan cover on the rear of the shroud. This will
allow the alternator/fan assembly to be removed.
The fan housing can be removed completely at this point if desired.
If the fan housing is simply raised, it helps to support it on
either side with wooden blocks. (It's really easier to just pull
the fan housing out of the car.)
the clamps on the two boots that connect the intake manifold pieces
together (two on each boot).
the shrouds from around the preheater tubes (if they are there).
the nuts and bolts that attach the preheater tubes to the exhaust
header. (You don't need to do this if you are not removing the center section of the intake manifold.)
the nuts (two on each side) that attach the intake manifold end
pieces to the cylinder heads.
loosen the hose clamps on the polyethylene boots that connect
the intake manifold end pieces to the intake manifold center section,
and lift off the end pieces.
the fan shroud enough to slip the manifold under it (if you have
not previously removed the fan shroud).
the nut that secures the center section of the intake manifold
to the engine block, and lift the intake manifold
center section off of the engine.
Manifold Installation Procedure -
and inspect the manifold, paying particular attention to the flanges
and preheater tubes. Remove any carbon buildup from the passages.
the flanges on the intake manifold ends to make sure there is
no foreign material on them and that they are not warped. This
can be a significant source of air inleakage. Sand the flanges
on a flat surface if necessary.
- Make sure there is a stud protruding from the engine case to
which the manifold tongue can attach. It is very important that
the intake manifold be snugged up tightly against the engine case
at this point.
- With the fan housing raised or removed, slip the center section
of the intake manifold under it and into place.
Since the manifold center piece has to slip under the alternator
stand, it is easiest to assemble the manifold piece-by-piece.
- Smear a thin layer of Permatex Ultimate Grey sealant (or similar)
on both sides of a metal dual-port intake gasket, and place the
gasket over the studs in the cylinder head on the right-hand side.
- Smear a thin coating of wheel bearing grease inside the lips
of the polyurethane boots.
The grease is not meant to be a sealant, but a bit of grease makes
the boots stay supple and allows them to be fully tightened up
by the hose clamps.
- Slip a new polyurethane boot and two clamps (note the size difference)
onto the right-hand side of the manifold center piece.
- Place the right-hand end casting down on the cylinder head studs
(no nuts or washers yet). At the same time, slip the right-hand
end piece into the polyurethane boot on the center piece, but
don't tighten the hose clamps yet.
This may be a tight fit. You may need to carefully tap the end
pieces in place with a hammer and drift.
- Fit the left-hand end piece the same way.
- Tightened all four of the end-piece/cylinder head nuts evenly
and securely (tight but not TOO tight - the studs in the cylinder
head aren't very big).
- Install the pre-heat tubes into the intake manifold center piece,
and attach the flange on the other end to the exhaust header with
bolts, washers and nuts. Tighten securely.
In the aftermarket intake manifolds that are available today,
the pre-heat tubes come as separate pieces. It may be necessary
to bend the tube a bit to make them fit, both into the holes
in the center section of the intake manifold and where they
attach to the exhaust header. If you find it necessary to bend
them, do so carefully so the tubes doesn't become kinked.
- Tighten the four hose clamps on the two polyurethane boots that
connect the intake manifold pieces together.
- Make sure the top of the manifold is level (assuming the surface
you are working on is level), then bolt the manifold tongue on
the bottom of the center section of the manifold to the stud that
protrudes horizontally from the engine case, using a large washer
and 13mm nut. Make sure the manifold tongue is resting tightly
against the engine case.
If you may find (as I did) that the stud in the engine case to
which the manifold tongue is too attach appears to be too short
to get a nut on it. This is probably because you do not have the
manifold tongue snugged up tightly against the engine case. And
this may be because the pre-heat tubes are installed incorrectly
in the center section of the intake manifold.
- Lower the fan housing partially into place, keeping it raised
enough to replace the alternator/fan assembly and the four mounting
bolts that hold it in place (if you removed the alternator/fan
- Lower the fan housing the rest of the way and attach the two
bolts on either side.
If these two connectors are cheese-head screws, replace them with
10mm hex-head bolts. This will save you lots of trouble reinstalling
them and removing them next time (10mm open-end wrench instead
of an offset screwdriver).
You may need a flat-head screwdriver to pry open the cylinder
tin slightly to accommodate the shroud. (The shroud tin goes INSIDE
of the cylinder tin, all the way around.)
- Install and connect the connecting link between the cooling
flaps in front of the fan housing. Be sure to properly install
- Screw the thermostat back onto the connecting rod and adjust
and tighten the thermostat in place. See our
Thermostat Installation procedure.
- Replace the oil cooler hot air exhaust and the oil cooler cover
with 10mm hex-head bolts.
- Replace the engine lid hinge brackets and the engine lid.
- Reconnect the fresh air tubes on either side of the fan housing
and the ignition cable into the coil.
- Reattach the spark plug wires to the spark plugs (if you removed
them) and the wires into the attachments in the fan housing (three
- Replace the strap that holds the alternator to the alternator
- Reconnect the wire to the backup lights, reinstalling the in-line
fuse in the process.
- Reattach the electrical connectors to the alternator.
- Reattach the cable to the negative terminal on the battery.
- Replace the accelerator cable guide tube that runs through the
fan housing and run the accelerator cable back through it into
the engine compartment.
- Replace the carburetor and reinstall the idle cutoff valve.
- Replace the distributor (if removed) and the distributor cap.
- Replace the wire to the automatic choke.
- Replace the fuel line to the fuel pump and from the fuel pump
to the carburetor and snug down the hose clamps on either end.
- Re-attach the accelerator cable to the throttle lever by way
of the barrel clamp at the base of the throttle lever.
- Replace the air cleaner.
- Replace and adjust the drive belt. See our Drive
Belt Replacement/Adjustment procedure.
Sit down and enjoy a cold one. You deserve it! Then take your baby out for a spin and notice that she doesn't stumble on acceleration any more!
Some Questions and
came up regarding the reasoning behind the three-piece manifold.
It seems like this just gives the VeeDubber one more thing to watch
for, the guy wrote, to make sure air isn't getting sucked into the
manifold around those rubber expansion joints.
Rob responded - The ‘71 model got the 34PICT/3 carburetor and three-piece
manifold. My theory is this -- (regarding the one-piece/three-piece
switch)-- the cylinders actually 'walk' front/ back, and up/down
a few thousandths when the engine is running (the heads are clearanced
to allow for this). Also the iron cylinders and aluminum heads expand
at different rates with. This makes the engine change shape fractionally
with heat. The one-piece manifold, with it's soft copper gasket
at the heads, is probably at the limits of it's capacity to stretch
with this engine movement on the 1500cc engine (it runs colder than
the engine remember, so doesn't expand as much), and with the greater
heat of the 1600cc engine, they needed to alter the design.
I also wonder if the VW engineers weren't anticipating an extended
stroke for another increase to say 1700cc. An extended stroke would
have required a wider engine, and the three piece manifold could
cope with this okay.
A question regarding the differences in head design - On p. 1-17
of the Bentley manual there is an exploded view of the cylinder
head. Two heads are shown: the 1970 head, and the 1971 and later
head. The major difference appears to be that the 1971 head is dual
port, whereas previously the head was single port. Is this correct?
And as I look at the 1971 head it shows two studs that the intake
manifold attaches to. It is at this point that there is a compressible
copper gasket, right? If the nuts are not sufficiently tight this
would be a very likely place for air inleakage. I don't find a torque
specification for these nuts in the Technical Data section; do you
know what torque they should be tightened to?
responded - In 1970 the U.S. got the first 1600cc engine, but that
was with the single port heads, same as my 1500cc engine. I think
the valve sizes may be a bit larger on the twin port heads too.
I'm fairly sure the gaskets on the dual port are paper or fiber.
Motorworks catalogue has a photo of a twin carburetor setup with
the gaskets on the right hand side (black -- 'double ring' shape).
I don't remember the torque setting -- but it wasn't very much (small
The '71 manifold was also designed for the 34 PICT carburetor.
The 34PICT came with the first 1600cc dual-port engine in the ‘71
model year. ’71-‘73 had the dual vacuum distributor with the 34,
then '74+ got the single-vacuum dual-advance (SVDA) distributor
and still kept the 34 PICT carburetor. There IS the possibility
that the ‘71/’72 manifolds (with generator) were a little different
to the ‘73 (with alternator -- larger diameter), but I haven't heard
of any difference (which doesn't mean much as I have less knowledge
after ‘70 than before).
A question - I've been having a frustrating time myself getting
the old manifold out and putting the "new" one back in. Can you
give any advice?
Dave responded - On my '73 SB I have to strip pretty much everything
off of the engine (carburetor, alternator, etc.) to get the intake
manifold out. And to do that, of course, it's just easiest to remove
the fan housing.
Rob responded - I found that by removing the left dual port "corner"
manifold piece and lifting the fan assembly with generator attached
I could finangle the new manifold centre section in. Since my Bug
doesn't yet have cooling flaps back in (hard to find here -- almost
all VW's have had them removed and junked!) I could lift the fan
without worrying about the thermostat linkage.
Rob reports experience with an engine running on only two cylinders
- The two right cylinders are running, so you know you're getting
petrol into the system. And you know that the two plugs on the left
are firing, which means that somehow between the carburetor and
the cylinders the fuel mixture on that side is outside the 1.4%
- 7.6% flammable range for petrol. There's no way it could be high,
so excess air in the system on that side is the only logical conclusion.
I even tried pulling back the rubber boot on the left side of the
manifold to see if I could spray WD40 in there for a test, but the
right cylinders wouldn't fire with the left boot off. It was this
which finally made me think it MUST be the left dual port manifold
piece, since that was the furthest away from the right cylinders
which were obviously getting a "close enough" mixture to run.
Finally I just sat and looked, then tried moving the left rubber
boot to try the WD40 trick at the left cylinders, which settled
the thought about where the leak had to be, even though I couldn't
see it and WD40 near the head/manifold joint didn't make any effect
(couldn't get the straw right down there, and the leak must have
been over too wide an area).
(Later) It turned out to be the removed dual port manifold piece
which had not snugged down properly. When it's in the car, the bolts
for that piece are almost impossible to reach -- socket with 1-foot
extension bar for the front nut and an open-end spanner for the
rear bolt, turning it 1/12th turn at a time and flipping the spanner
over each 1/12th (the heads are angled 1/6th turn). So it had not
bedded down and I couldn't see that from above it. After loosening
and a good wiggle I got an extra 2-3 turns on the nuts and it's
fine now. Idles smooth, lots of power.
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