Road Race Home
Throttle Body Swap
Using a 1G CAS Option
Installing the 95-96 sensor in the original position:
The cam angle sensor mounting points that need to be duplicated
Plotting out the correct location for the mounting holes that need to be
drilled and tapped
Clearancing the head for the screw heads that are on the back of the
intake cam gear.
Clearancing finished. You can also see the welded up areas that will be
ground flat, then drilled and tapped.
Ground flat to the correct height
Holes marked by plotting distances from other bolt hole on the head
and using the 2G head for comparison.
Using a center punch to help start the drill in the correct spot.
Drilling holes, be careful with the depth, you can drill into the
interior of the head. If you do, epoxy on the bolt will fix it right
up... don't ask.
Tapping the holes with a 6mm x 1.0 bottoming tap.
Filling in the water fitting on the front of the block. It
can be blocked off with a bolt but the banjo bolt often breaks off when
trying to remove it so we will end up welding it closed.
Shifter counter weight removed.
1G water pipe installed.
Swapping a first generation cylinder head onto a second generation
For anyone considering the conversion these are the parts you need,
preferably from a late (May) '92 thru '94 motor:
- Cylinder head, with a fresh valve job, might as well do some
porting while you have the chance but it isn't necessary. Best to
use a May/92 and up head but a 90-91 head will work too, even a
90-94 non turbo head. The May/92 and up head has better cooling
passages running between the head and block.
- Stock head gasket or HK$ head gasket and ARP head studs if you are
trying to be the king.
- Intake manifold and gasket, can be from any year 1G turbo, they
are all the same
- Throttle body and gaskets (2) (MUST be May/90 and newer, 4 hose
fittings on the top, 3 straight and one angled)
- Coil pack and bracket (MUST be May/90-newer)
- The big water pipe on the front of the motor (MUST be May/90-
- The complete water neck assembly on the side of the motor (MUST be
- The "u" shape water line that goes under the turbo (any
- A new bracket needs to be made to hold the igniter assy. in about
the same position as it sits on the 2G.
- If you are going to be keeping the EGR system, a chunk of aluminum
needs to be fabricated to bolt the MAP sensor to and that piece gets
welded on top of the "EFI MULTI" on the 1G manifold.
Its only purpose is to check EGR operation.
- If you toss the EGR, just make a EGR block off plate.
- Slight clearancing to the cam cap area behind the intake cam gear
for the screw heads on the back side of the cam gear.
- The big ugly weight gets cut off the shifter to clear the lower
- Fill or plug the water fitting on the front of the engine block.
- Re-use the 2G throttle position sensor. It bolts right up to the
- The vacuum hoses at the throttle body all need to be lengthened so
that they come in from the passenger side.
- Time to do a new timing belt
There are two ways to deal with mounting the cam angle sensor when
swapping to a 1G head.
The 97-up style cam angle sensor will bolt to the 1G head without any
modification. The wire connector is different so you will need to make a
connector for it or get one from a wrecking yard to plug in the wires.
The main difference in the sensor is that it gives an opposite pulse
from what the 95-96 sensor does. There are two ways to deal with it.
(This also applies to swapping a 95-96 ECU with a 97-up ECU)
1) At the ignition coil, connect plug wires from cylinders 1 and 4 into
the coil for 2 and 3. Connect
the plug wires from cylinders 2 and 3 into the coil for 1 and 4.
or 2) At the smaller coil wire electrical connector, swap the trigger
wires for the two coils. Cut the blue/red wire and the blue/black wire.
Swap them and reconnect them.
If buying the 97 cam angle sensor parts new from the dealer you will
need the following:
The Sensor and the bolt that holds it on.
1) MD327107 Sensor, Camshaft Position
1) MF140003 Bolt, 6mmx 12mm
The cast aluminum housing assembly that holds the sensor.
1) MD344722 Support, Camshaft Position Sensor
1) MD329502 Cover, Camshaft Position Sensor
1) MD329503 Gasket, Camshaft Position Sensor
3) MF140204 Bolt, Cover 6mm x 14mm
2) MF140025 Bolt, Support 8mm x 20mm
The piece that bolts to the end of the camshaft and the bolt itself.
1) MD327621 Cylinder, Camshaft Position Sensor
1) MF241261 Bolt, Camshaft
Expect to pay between $100 and $150 for the parts depending on the
We find it cheaper to modify the 1G head to fit the 95-96 sensor when
doing a swap here in the shop. A guy in the middle of nowhere with out
the equipment to weld aluminum and fit the 95-96 sensor under the intake
cam gear will have an easier time by using the 97-up sensor.
To install the sensor fitting onto the end of the intake cam, you will
need to drill and tap the end of the intake cam to be able to bolt on
the 97 fitting at the end. All DSM cams have the drive slot there for
the fitting, the drive slot is the same as the slot for the 1G cam/crank
angle sensor. In the end of the cam there is a dish shape that makes
starting the drill in the center easy. We stand the cam up vertically
and use a drill press to drill straight down into the end of the cam.
The casting drills easily and it could even be done with a hand held
drill if you are experienced. Tap the hole with a 8mm x 1.25 bottoming
tap. Even if you _slightly_ skewed the hole at an angle, it will not
affect the sensor fitting. It is centered and held in place by the shape
of the end of the cam, just do it.
The wire colors are the same with the two sensors. You want the black
wire on the top, blue wire to the middle prong and red to the bottom.
If you are going to re use the 95-96 sensor, the most fun part is
building up (by welding) enough material under the intake cam sprocket.
These spots get machined flat and true so they can be tapped for a place
to bolt the 2G cam angle sensor on. It's got to be perfectly
This is only necessary on the '95-'96 cars. The '97's have the cam
angle sensor back on the passenger side of the head.
The throttle body now sits 1" further forward and may cause some
misalignment with your I/C piping.
If you use 1G cams on a '97-99, the end of the intake cam must be
tapped with threads for the new style cam angle sensor. (8mm x 1.25)
Why do all this? The 2G car has a little honda sized throttle body,
intake manifold, and intake ports. That is one of the big reasons the
2G's have better bottom end power but are a little slower at the drag
strip. Example: 1G intake port at the gasket is 60mm x 37mm, 2G measures
56mm x 28mm.... ouch! Throttle bodies are 1G - 60mm vs. 2G - 54mm
While a 1G head and intake manifold flow more than a 2G head and intake
manifold, too many people are in a big hurry to do the swap when
they have not maximized their current set up. Even a Cali car can run
well into the 11's on a stock 2G head and intake manifold. A well ported
2G head and Extrude Honed manifold will take you even further. If your
2G head dies a horrible death from a suicidal T-belt, go ahead and do
the swap while you are fixing things up.
Some guys want to just install a 1G manifold on a 2G head. The port
size between the two is quite different, you cant just bolt it on. The
2G head _can_ be ported to flow as much or more than an unported 1G head. But if you can get a decent deal on a 1G head why
bother ? I have seen some butchered up 2G heads with the 1G Look that
were a waste of time to bolt on. Just because you make it huge at the
gasket mounting flange does not mean it will flow any better. The real
HP gains are made deeper in the runner and the bowl area where it is
harder to get to.
The 1G cams have .010" higher lift. and are an upgrade by
Swapping just the throttle body gives
great response and increased top end power too, even with the stock
1G 60mm throttle body on the left, 2G 52mm throttle body on the right