Skunk2 P72 Intake Manifold Install
Author _ Katman
This article covers the installation process
of a Skunk2 GSR intake manifold (I/M) for the
P72 B18C GSR
head. This applies
to both JDM & US versions of the P72 head.
Upgrading to the Skunk2 manifold will unlock
potential top-end power by deleting the use
of the secondaries/dual-butterfly
system found on all JDM & US P72 B18C 'snail
shell' intake manifolds - by converting the
breathing habits to that of a Type-R single
butterfly I/M system. Although, there are ways
of enhancing the breathing habits with your
existing P72 I/M , the Skunk2 I/M is a great
alternative and is a definite bang-for-your-buck
upgrade. Not only does the Skunk2 manifold free
up top-end breathing, but it's a bolt-on power
maker of approximately 7-8 horses!
Read on for installation procedures...
If you want a clean looking intake manifold
setup, especially when it comes to the throttle
cable & bracket, get the following parts:
- Integra-R throttle cable bracket / Honda
part # 16411-P73-000
- Integra-R throttle cable / Honda
part # 17910-ST7-R01
- Throttlebody pulley from a non-GSR throttlebody
- A GS-R intake manifold gasket (if you can't
reuse your old one, for some reason)
- A GS-R throttlebody gasket (if you can't
reuse your old one, for some reason)
- Small Japanese hands
SUGGESTED TOOLS TO USE
- 12mm & 10mm socket (short + deep), rachet,
- 12mm & 10mm open/closed end (box) wrenches
- Phillips head screw driver
- Small pic or tiny flat head screwdriver
for injector clip removal
- Long bent-tip needle nose pliers for those
damn hose clamps
- Shop rags to collect any spills
- Small Japanese hands (a joke! geez, relax!)
To resolve this behavior, use the Regsvr32 tool
to unregister the Mobsync.dll file from the
- Begin, by raising the front end of your
car up and placing it on jack stands
- Disconnect the battery negative &
positive cables for safety purposes
- Drain the coolant into some kind of container
that you can cover, so dirt will not fall
in (if you plan to reuse) and/or animals
will not drink from it!
- MAKE SURE
NO PETS ARE AROUND!!!
If dogs or cats drink coolant they have
a pretty good chance of DYING from it, if
not caught in time - NO JOKE! Coolant crystalizes
in animals kidneys and will give them a
- Loosen up your gas cap to relieve gas
pressure from the fuel tank
- Start disconnecting all vacuum & radiator
hoses/lines from the intake manifold using
the long needlenose pliers (real handy!)
- Disconnect sensor plugs, injector plugs
(use a pick), etc., from the intake manifold
- Take the 12mm socket + ratchet and loosen
up the fuel filter pressure-release bolt,
some fuel will leak out, so have a rag handy
- Using a 10mm socket, remove the black
plastic wire harness cover from the fuel
- Remove the vaccum hoses from the FPR (fuel
- Again, using the 10mm socket, carefully
remove the nuts that hold the fuel rail
down to the I/M. CAREFUL!
those small 10mm screws can easily fall
out of your hands and can get easily lost
behind the engine - I hate when this happens!
- Carefully wiggle the fuel rail off. The
injectors will probably come off along w/the
rail. Try not to damage or rip the rubber
o-rings that are on the injectors. Also,
try to not lose the round black grommets
that hold the injectors in place
- Place the fuel rail w/injectors still
attached to it, somewhere out of the way,
even though the rail is still attached to
the fuel filter hose. Just get it outta
the way, near the battery somewhere, you
don't need to fully remove it.
- [ Support Bracket Removal ]
If your OEM P72 intake manifold has never
been removed (you're in for a real treat),
there's an annoying bracket on the backside
which needs to be removed. It attaches from
the underside of the P72 I/M to the backside
of the engine block, as a support bracket
for the heavy-ass OEM P72 I/M. You don't
need to use it on the Skunk2 I/M if you
don't want to.
- Get underneath your car so you can see
the underside of the GSR manifold and the
lame support bracket
- Use a ratchet with a nice long extention
to reach the two 12mm bolts
and remove the support bracket. See
- While you're under there, disconnect any
sensors/hoses/etc. that are still connected
to the P72 I/M, such as the IAB sensor (black-round
canister mounted on the underside of the
GSR manifold). Loosen up and remove all
of the 12mm flange nuts that are holding
the P72 manifold to the head from the underside
- Then remove the rest of the 12mm flange
nuts from the topside of the P72 I/M
- [ Prepping the Skunk2 I/M ]
Once you're done removing all 12mm
flange nuts, double check that all sensors,
vaccum lines, and any coolant lines are
not connected to the P72 manifold
- If everything looks go-2-go, carefully
remove the P72 manifold. See image
- Once removed, using a 12mm socket, remove
the TB from the P72 manifold and carefully
peel the TB gasket off using a razor blade
to helps a lot. You wanna try and preserve
the TB gasket and reuse it.
- Next, you will prep the Skunk2 I/M, by
swapping over the P72's fuel rail, TB mounting
posts, and required sensors
- You can start off by removing the P72
fuel rail mounting posts using two of the
10mm fuel rail nuts. See image 5.
- Next are the TB mounting posts. Remove
and apply these posts using the same technique
as used on the fuel rail posts
- Next are the sensors. Swap over the IAT
and IACV sensors. See image 6 &
- Then apply the ITR throttle cable bracket.
See image 8.
- Lastly, swap over the rubber fuel injector
grommets onto the Skunk2 manifold. See
- [ Throttle Pulley Swap ]
Now that you're temporarily done
fussing w/ either manifold, it's time for
throttlebody (TB) adventures!
- Now, I'm assuming you've acquired a non
P72-GSR throttlebody pulley. If you haven't
done so, get one! See image 10.
any 88-01 civic/integra NON P72 TB throttle
pulley will work on a P72 TB
- Use a 10mm socket to remove the P72 TB
pulley. Then apply the NON P72 TB pulley.
Note: You *might* have
to fiddle around with remounting the retensioning
spring a bit, but its not hard to figure
- Next, remove the big funky P72 throttle
cable support bracket thats directly on
the P72 TB. See image 11.
- The P72 TB is ready -- that wasn't too
bad now, was it ? (naaw!).
If you'd like to, you can mount the prepped
P72 TB onto the Skunk2 I/M now. Reuse your
P72 TB gasket IF you haven't
fully damaged it!
- Now, go install the Type-R throttle cable
in your vehicle. It's pretty straight forward,
so I'm not including the how-to procedure
- [ Prepping the PCV Valve ]
Once you're done installing the ITR throttle
cable in your vehicle, go back to your engine
bay and take a look at the area where that
bloody I/M support bracket lives.
You should see the factory oil catch can
with 2 lines plugged into the topside. This
is where the PCV valve lives. See
- Once you've pulled out the PCV valve,
get a lenghtly vaccum or coolant tube and
attach it to the PCV valve. Then plug the
PCV valve back into its respective location
(for a test fit). See image 13
- Now, take the pre-prepped Skunk2 I/M
and place it on the head as if you're about
to bolt it on. Slip the PCV tube up and
in between the manifold's runners till it
reaches the vaccum spout in the middle of
the plenum. See image 14.
- [ Finishing Touches ]
If the PCV tubing looks like it will fit
without binding problems or anything of
that nature, its ready.
- Check to see if all coolant lines can
be put back to their orginal location. If
you're like me; I like to bypass the coolant
lines which run to the TB's fast idle throttle
valve (FITV), located on the bottom side
of most TB's. Although, bypassing
the FITV is not a good idea if you live
in a cold weather climate zone!
- Once you're done overlooking your coolant
routings, tighten down all of the 12mm flange
nuts to a good snug or to factory torque
spec (that is, if you can reach a torque
wrench down into those tiiite spots)
- Apply the P72 TB to the Skunk2 manifold
if you haven't done so yet
- Fit the PCV valve and coolant lines back
to their respective locations
- Remember the fuel rail & injectors?
Well, it's time to re-install those. Use
the 10mm nuts to secure the fuel rail to
the fuel rail posts, then connect the fuel
pressure regulator vaccuum tubing.
NOTE: The brown ceramic
spacers that sandwich in-between the fuel
rail + manifold are NOT USED.
To check this, make sure that there are
no loose gaps between the fuel injectors
and fuel rail. If there is a gap and the
injectors sit rather loose, remove
those ceramic spacers! or else
you'll have leaky fuel injectors! And because
those ceramic spacers are not used, the
fuel rail will sit lower on the mounting
posts, and you just might have to elongate
the mounting holes on the fuel rail to comply
with the mounting posts. You'll see what
- Connect the throttle cable's hammer-end
into the throttle pulley; then mount the
cable to the throttle-cable bracket. Make
sure you're getting full throttle too. Have
someone sit in the car while stepping on
the gas pedal and look into the TB and see
if the brass butterfly inside the TB is
opening all the way. Adjust the throttle-cable
if the butterfly isn't opening all the way
- Re-connect all of the sensors (MAP, TPS,
IAT, IACV, etc)
- DON'T FORGET:
To tighten down the 12mm fuel pressure
release nute on top of the fuel filter!
- Re-tighten your gas cap.
- Re-fill your radiator fluid, either with
new coolant or reuse your previous coolant.
- Double-check that everything is OK, connected,
lookin' good, etc.
- If all is good, get in your car and turn
your ignition on 2 clicks and wait
+ listen for the fuel pump -
but don't turn the car on yet!
This will build up fuel pressure. Leave
the car on and go check your engine bay
and see if there's any fuel leaks or spray
coming from the fuel injectors, fuel rail,
or fuel filter. There shouldn't be any leaks
if everything was put back correctly. If
no leaks - so-far-so-good! Now, go ahead
and fully turn the engine on (3rd click).
It might take a couple turns for it to kick
over, so don't trip, it'll start.
- Once running, check for coolant leaks
etc, if all looks good you're install is
If you have any funky, high or irradic idle
problems, double-check any vacuum lines
or any unplugged sensors. Maybe toy around
with your idle-adjustment screw on the TB.
Lower the car back down to the ground, go
for a test drive, and clean up ya' damn
By now, you should know that a Skunk2 I/M
uses a single-butterfly design, and an OEM
P72 I/M uses a dual-butterfly design. Well,
a stock P72 ecu doesn't know
that you changed over to a single butterfly
style intake manifold, and seeing that the
Skunk2 manifold is essentially a Type-R manifold,
you'll need to adjust your ecu for this change.
Mainly, the VTEC crossover point needs to
Here's a few options:
- Option 1)
You can run your stock GSR ecu as-is for the
time being, but peformance wise, it will not
feel right with the stock VTEC crossover point
kicking on at approx. 5000rpms...so..
- Option 2)
Purchasing a VTEC controller is suggested,
so you can raise the VTEC point up to about
- Option 3)
Have your ecu reprogramed (chipped). If you
have an OBD1 P72 ecu have it reprogrammed
(by me!) w/ a customized VTEC, redline, &
fuel maps. If you own an OBD2 vehicle, I suggest
converting to OBD1 or running a Type-R ecu.
Although, if you go with this route, I suggest
that you upgrade your camshafts to at
least civic or integra type-R cams (you
don't have to - its suggest tho). Actually,
you should upgrade your camshafts anyways,
to benefit even more gains from the Skunk2
The information in this article applies
- US (B18C1) or JDM (B18C) P72 B-series