Chevrolet Impala SS, Handbook

Page: 84 / 159

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SSHandbook
Modifications: Electrical
Procedure:
1. Remove the black bezel surrounding the instrument cluster by removing the two bolts at the top of it and
pulling it back away from the dash. There are three clips at the bottom in the back and two guide posts. Be
careful with the rubber ring that goes around the steering column as it is held on by some flimsy plastic
rivets and cannot be reattached easily.
2. The tachometer will go in the right hand side of the black plastic in the bezel to avoid interference with
the turn signal and tilt levers and to allow the sacrifice of one of the two clips on the right if need be (the
left has but one). If you're careful, you can keep both of them. It will need to rest on or near the point
where the smooth grey plastic ends and the molded grey plastic for the rest of the dash begins. Using the
tabs and holes as a reference, find where the center ofthe tachometer should be ifit would rest about 1/8"
above the lip and mark the spot on the back ofthe bezel.
3. Using a 2" hole saw and starting from the back of the bezel, cut out the hole for the tachometer. If you
screw it up, don't worry: the bezel is only $15 and you can always try again.
4. Trial fit the tachometer. If it doesn't fit, work around the exterior of the hole with an Exacto knife until it
does. Don't cut too much: it should fit tightly.
5. Cut an identical 2" hole out ofthe grey plastic behind the bezel. You can re-insert the bezel and use it as a
guide. The tachometer will angle downward slightly, so take this into account.
6. Again, trial fit the tachometer. You may need to cut into the two slots for the clips. Make sure the
tachometer fits in below the clear instrument cover and does not bind. It'll be tight but it will fit. Keep
trimming the grey plastic until it does. Repeat ad nauseum. You might need to cut into one of the
rectangular holes for the clips to make it fit.
7. Once it fits in well, make sure the wires are routed so that they'll dangle into the are below the instrument
panel and replace the bezel.
8. Remove the access panel below the steering wheel by removing the two screws on the bottom of it. Then
remove the steel plate behind it by removing the four bolts and pulling it to the right. The wires for the
tachometer should be dangling down there, or at least accessible from there. Installing a four-way
connector here would be a good idea in case you ever need to remove the tachometer.
9. Tap in a "dimming" or "lights on" signal. The ashtray has both dimming lead and a ground wire going to
its light. The wires are also free enough to work with. The grey wire is the dimming wire, and the black
wire is the ground.
10. To get power to the tachometer, you might want to tap into one of the orange wires at the bottom of the
fuse box. Check the Helm's manuals for details: you want one that is only hot during run.
11. To get the actual tachometer lead hooked up, you need to route it through the firewall using a factory,
unused grommet. Look behind the LH wheel well. There is an oval, rubber piece there. Now remove the
LH kick panel and look near the point where the hood latch cable exits. If you pull back the insulation,
you'll see the same grommet. Use a sharp point to poke a hole in the plug in the firewall, and then squeeze
the 18 gauge wire through it. You might have to fish it through using a coat hanger or something.
12. The tachometer can take its signal from the black and white wire (negative) terminal at the coil pack on
the front of the LH cylinder head. Alternatively, another member has plugged the lead into fourth, unused
female terminal on the coil. The both go to the same spot.
13. Another good place to get a tachometer signal would be from the PCM connector pin A13. All B/F-car
PCMs output the tachometer signal on this pin. You will need a terminal p/n 12084913 (for 20 ga. wire) to
install in the PCM A connector (the factory uses a white wire for this application).
14. The wires should be inserted inside of factory wire loom. You can cut a short length and route to one of
the factory conduits from the firewall grommet, or route a new conduit all the way to the coil pack.”