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Click here for additional LT-1 specific wiring info

Wiring Modifications By Circuit...

Starter Wiring...The wiring for the Chevy starter is almost identical to that of the RX-7. The only real difference is the type of connector for the "S" terminal on the solenoid. (the "S" terminal stud is the small stud closest to the block). The Mazda harness has a female "spade" type connector, the Chevy uses a small 3/16" "ring" style terminal. The problem is that this wire was part of the engine harness, which was removed with the rotary engine. You can access this black w/ yellow stripe wire at connector X-12 (listed in the harness ID section).
...Manual trans T-5 and T-56 applications...Route a wire from X-12's black w/ yellow stripe wire that extends to the Chevy solenoid's "S" terminal.
...T-350/T-400/2004R/700R4/4L60E automatic trans applications...Route a wire from connector X-12's black w/ yellow stripe wire that extends thru your neutral safety switch, then to the Chevy solenoid's "S" terminal. Be sure that the neutral safety switch interrupts this wire in all shifter positions except neutral and park. If it does not, adjust the switch until it does.

Alternator Wiring...Mazda routed the alternator wires differently depending on model...
'70-'80 models...If you are using the stock '79-'80 RX-7 alternator, connector X-01 contains 2 wires that need to be extended to connect w/ the RX-7 alternator...
.........black w/ yellow stripe... needs to be connected to the RX-7 alternator's "N" terminal.
.........white... needs to be connected to the RX-7 alternator's "E" terminal.
'81-'85 models...The alternator wiring for the '81-'85 models was routed within the engine harness, which was removed with the rotary engine. You can access these wires at the front harness's connector X-01 (listed above in the harness ID section), where they should be extended to your Mazda alternator's new location. You can recover the needed "T" shaped alternator connector from the rotary engine's discarded engine harness.
.........black w/ white stripe... this wire connects to the RX-7 alternator thru the small "T" shaped plug. This wire plugs into the top part of the T.
.........white w/ black stripe... this wire connects to the RX-7 alternator thru the small "T" shaped plug. This wire plugs into the bottom "leg" of the T.
For those wishing to run a Delco alternator, here are some info on wiring some of the more popular models into your RX-7's harness...
'75-'84 Delco 10-SI...in addition to the large insulated "batt +" stud terminal on the back, these alternators also have a smaller 2 wire connector socket labeled "1" and "2". The stock GM harness plug for these terminals used the following wire colors, and should be connected as follows...
.........terminal "1" (brown or orange wire)...connect this wire to your RX-7's black w/ white stripe alternator wire thru a 10ohm 6watt resistor. If you have problems with your car running on after the key is turned off, substitute a diode for the resistor (arrow pointing in the direction of the alternator).
.........terminal "2" (red or black w/ red stripe wire)...connect this wire to the large insulated "batt +" stud on the back of the alternator.
'85-'89 Delco...in addition to the large insulated "batt +" stud terminal on the back, these alternators also have a smaller 3 wire connector socket labeled "L", "F", and "S". The stock GM harness plug for these terminals used the following wire colors, and should be connected as follows...
.........terminal "L" (brown wire)...connect this wire to your RX-7's black w/ white stripe alternator wire thru a 10ohm 6watt resistor. If you have problems with your car running on after the key is turned off, substitute a diode for the resistor (arrow pointing in the direction of the alternator).
.........terminal "F" (brown or tan w/ white stripe wire)...connect this wire to the large insulated "batt +" stud on the back of the alternator.
.........terminal "S" (red wire)...connect this wire to the large insulated "batt +" stud on the back of the alternator.
'90-'98 Delco...in addition to the large insulated "batt +" stud terminal on the back, these alternators also have a smaller 2 wire connector socket. The stock GM harness plug for these terminals used the following wire colors, and should be connected as follows...
.........brown wire...connect this wire directly to your RX-7's black w/ white stripe alternator wire.
.........red wire...connect this wire to the large insulated "batt +" stud on the back of the alternator.

Ignition Wiring...Power for your Chevy engine's ignition system should come from connector X-01.
...black w/ white stripe... There are 2 of these wires that went to the rotary engine's ignition Coils, that were located on the inner fender panel ahead of the driver's side strut tower. Power comes from a 40amp fusible link, and is turned "on" when the ignition switch is in either the "start" or "run" positions.

Locating & Re-wiring The RX-7's Fuel Pump / Fuel Pump Relay...Mazda changed the fuel pump control circuit in '84. Modifications are listed below...
...'79-'83 models No modifications required here for carbureted V-8 applications. Mazda wired the fuel pump to be directly controlled by the ignition switch, and used no relay at all. Power comes thru a 10A fuse between the ignition switch and fuel pump. The color of the wire between the fuse and pump varied a bit. '79-'80 used a black w/ white stripe wire. '81-'83 used a black w/ lt green stripe.
...'84-'85 12A carbureted models... The fuel pump was controlled by the "fuel pump cut relay", which was controlled by the rotary engine's ECU. The "fuel pump cut relay" is no longer needed and can be removed. When it is removed, the following modifications are required at connector B-06, which formerly plugged into the removed relay.
.........black w/ white stripe... This wire comes from a 20A fuse that gets it's power from the ignition switch in the "start" & "run" positions. Connect this wire with the blue w/ white stripe wire in this B-07 connector.
.........blue w/ white stripe... This wire goes to the "+" side of the fuel pump. Connect this wire with the black w/ white stripe wire in this B-07 connector.
...'84-'85 GSL-SE 13B fuel injected models Mazda calls the main fuel pump relay the "Circuit Opening Relay", a square relay with a 6 terminal connector B-29 (2 rows of 3), which is located under the steering column. The ignition switch sends power to one of 2 coils in the circuit opening relay. The "run" coil gets it's power from the ignition switch in the "run" position. The ground leg of this coil (brown wire in connector B-29) goes out to the airflow meter, where it is grounded when the airflow meter senses actual flow. If the ignition is on, simply grounding this wire will close the relay contacts and power up the fuel pump. When you install a V-8, you remove the rotary engine's airflow meter, which dis-ables the fuel pump with the ignition switch in the "run" position. The airflow meter performed an important safety function, which was to shut off the fuel pump if the ignition switch was on but the engine was stopped. This situation could occur during an accident in which the engine stops but the driver is unable or does not think to shut off the ignition, so the fuel pump keeps pumping fuel, possibly creating a dangerous situation. Simply grounding this brown wire would dis-able this safety feature. A solution is to use either an oil pressure switch or an "inertia switch" such as that used by most all fuel injected Ford passenger cars. These switches are available inexpensively in most any wrecking yard, and are typically located on the passenger side behind the rear wheels. They are typically located behind a removable panel, and have a "reset" button.

Temp Sender Location & Installation...The RX-7's rotary engine's temperature sending unit for the dash gauge is a very small single terminal device located below the rotary engine's oil filter. It can be removed from the rotary and installed in your V-8' cylinder head (between the #1 and #3 exhaust ports) using a special reducing bushing. The original connector for the sending unit, connector C-02, can be salvaged from the discarded engine harness and re-used here for a factory quality connection. After installation, the sending unit should be connected to one of the following...
...'79-'83 models... yellow w/ white stripe wire in connector X-01.
...'84-'85 12A models... yellow w/ white stripe wire in connector X-08.
...'84-'85 13B models... yellow w/ white stripe wire in connector X-10.

Oil Pressure Sending Unit Wiring... The early '79-'80 RX-7 did not use a pressure gauge, only a low oil level light. Beginning in '81, the rotary engine's oil pressure sending unit for the dash gauge is located large round single terminal devive located below the rotary engine's oil filter. It can be removed from the rotary and installed in the rear of your V-8's engine block (located just to the driver's side of the distributor in the top/rear of the block) using a 1/8" pipe thread 45 degree elebow fitting (male threads for the block, female threads for the sender). A single wrap of the threads with teflon tape should ensure leak free operation. After installation, the sending unit should be connected to one of the following...
...'79-'80 models... Yellow w/ red stripe... this wire used to go to the oil level sensor on the rotary engine. When this wire is grounded, the oil level warning lite on the dash will come on. You can connect this wire to a Chevy oil pressure warning lite switch, and your RX-7's oil level warning lite will come on with low oil pressure.
...'81-'83 models... connect the oil pressure sending unit to the brown w/ yellow stripe wire in connector X-01.
...'84-'85 12A models... connect the oil pressure sending unit to the brown w/ yellow stripe wire in connector X-08.
...'84-'85 13B models... connect the oil pressure sending unit to the brown w/ yellow stripe wire in connector X-10.

Tachometer Signal Wiring...The RX-7's tachometer originally got it's signal from the ignition system's trailing coil/igniter, originaly located on the inner fender panel ahead of the driver's side strut tower. The tach was connected to the coil/igniter "-" terminal.
...'79-'85 all models... yellow w/ green stripe...This wire needs to be connected to the V-8's tach signal source, typically either the "-" side of the ignition coil or the "tach" terminal of the electronic ignition box.

Back-up Lite Switch...To operate the RX-7's back-up lites, Mazda used a transmission mounted SPST switch to complete the circuit. When the RX-7's engine harness is removed with the rotary engine, part of this circuit is removed as well. To restore this circuit, a harness extension will need to be added at connector X-12 ('79-'80), X-10 ('81-'83), or X-09 ('84-'85) a rectangular 6 pole connector (2 rows of 3) located under the hood on the driver's side of the brake master cylinder. 2 of the wires in this connector are for the back-up lite switch. These wires wires are...
...green w/ yellow stripe... comes from 15a fuse in underdash fusebox.
...red w/ white stripe... goes to back-up lites.
Connecting these two wires together w/ a jumper wire will turn on the RX-7's back-up lites when the ignition switch is in the "ignition" and "start" positions. Routing and connecting these two wires to your new transmission's back-up lite switch will enable the RX-7 back-up lites when "reverse" position of the shifter is selected.

Low Coolant Level Warning Buzzer and Lite...the original sensor for this circuit was located in the RX-7's top radiator tank. If you do not want to go to the trouble to keep this part of the warning system intact, you can either dis-able the buzzer (located on the outside/bottom of the dash pod), or, simply locate the brown wire that formerly went to the coolant level sensor and connect it to ground. If you need help locating this wire, it is part of the front harness, a single wire leg that comes out of the front harness just in back of the passenger side headlite.

Low Oil Level Sensor Wiring Modifications...If you have an LT-1, you may already have a low oil level sensor installed in your oil pan. Problem is, the RX-7 sensor and the LT-1 sensor work exactly opposite of each other. With the RX-7 sensor, low oil level closes a reed switch, grounding one leg of the warning lite bulb, causing it to illuminate. With the Chevy sensor, low oil level causes the ground leg to be opened. If you want to retaining this function you will need to use a relay to make the sensor compatible with the warning lite circuit.

Click here for additional Tuned Port specific wiring info
Click here for additional LT-1 specific wiring info


MAZDA RX-7 Tachometer Re-calibration

Re-calibrating the stock RX-7 tach for V-6 or V-8 use is a fairly straight forward process that involves dis-assembly of the dash, and removal of the tach assembly. The 1st step is to remove the whole dash pod from the car. There are 2 harness connectors to dis-connect from the rear, as well as the speedometer cable (a retention tang must be compressed to dis-connect the cable). After the pod is out, the dash face can be removed, usually attached with 4 phillip's head screws. Then the tach itself can be removed from the front of the main dash circuit board by removing the screws or nuts on the back side that connect it to the circuit board (depending on the model). Try not to leave any fingerprints on the satin black inner part of the dash face, as they are quite hard to remove.

After the tach is removed from the dash, it must be wired up to a signal source, usually done by using 4 long jumper wires w/ alligator clips.

RX-7 tach layout
There are 2 different layouts used for the 1st gen tach, one that is connected to the dash circuit board with wires, the other with studs and nuts to make the connections.

If your tach has wires, the connections are as follows :

trigger" wire is the black w/ yellow stripe.
"ground" wire is the white w/ black stripe.
"12v +" is the black wire (usually connected to keyed ignition)

If your tach has studs, they will be arranged (looking at the back of the tach) with 4 in a row on top, and 2 below that are widely spaced. The 4 along the top are used for out of dash calibration. I refer to them as 1,2, 3, 4, from left to right. 1 being on the extreme upper left, 4 being the extreme upper right. They are as follows :

#1 is the signal, or "trigger" as I call it, usually attached to a coil negative (-).
#2 is the ground.
#3 is the 12v +, usually hooked to a keyed ign. source.
#4 is output for the over-rev buzzer. (not used during re-cal)

The re-cal process
PREFERRED SIGNAL SOURCE... an inexpensive 12v battery charger can be used as a deadly accurate signal source for the re-cal of your tach. This signal source is so steady and accurate that there is no need to compare the reading with another V-8 calibrated tach. Battery chargers typically use a rectifier bridge to convert the AC power source into DC. This turns the 60 hertz sine wave input into a 120 hertz ripple wave DC output. The ripple wave output is read as 3600rpm by the stock rotary calibrated RX-7 tach. For a V-6 application, an RX-7 tach should be adjusted to read this signal as 2400rpm. For a V-8 application, adjust your RX-7 tach to read this ripple signal as 1800rpm. Please note that you must use a 12v battery for a power source, and the battery charger as a signal source only. The ground wires for both the battery and the battery charger should be connected to the ground terminal of the tach.
NOTE: Be sure that the RX-7 tach is about the same orientation as when installed, because the re-calibration may be off if done with the face in a horizontal plane.

Use the test leads to hook-up your RX-7 tach to the signal source and power source as described above.

With your signal source plugged in and your un-modified tach wired as above, it should be putting out a reading of about 3600rpms. To correct your RX-7 tach's reading, the cal-pot must be adjusted. It is a round white adjustable potentiometer located on the end of the circuit board near R3. The adjustment is secured from the factory with a locking compound, so your initial turn of the adjuster will be difficult until the locking compound's seal is broken. Be patient, and don't break anything.

...Early 1st gen tach...

...Late 1st gen tach...

When you get the adjustment free'd up you will be able to observe the effects of adjustment on the RX-7 tach's needle. Try to adjust until the tach reads correctly for your application (2400rpm for V-6, 1800rpm for V-8). If you don't have enough adjustment to get the correct reading, the value of the cal-pot must be altered.

The method we use is to add a 1000 ohm resistor in parallel with the resistor BEFORE the cal-pot (usually marked R3). I usually add this resistor to the backside of the board to make things easier. The 1000 ohm resistor will get the calibration close enough that minor adjustment of the cal-pot is all that is needed.

...Early 1st gen tach...

...Late 1st gen tach...

After adding the resistor, repeat the process. Now, the cal-pot should have plenty of range.

Troubleshooting FAQ...
"My test rig does not operate the tach..."
...Most likely, your battery charger is too good. The more expensive chargers have filters that remove too much of the voltage ripple while converting to DC. The needed cheap battery charger uses only a rectifier bridge to hack the AC into DC, resulting in a distinct ripple instead of a true straight-line DC voltage. You need to use the cheapest of the cheap chargers.

"My tach needle does not rest at zero..."
...The tach needle is a light "press-fit" on it's shaft. Simply forcing the needle against it's internal shaft stops will spin the needle on it's shaft. To re-index the needle, just lightly twist it against the shaft stop in the opposite direction.

"The 1000 ohm resistor does not give my cal-pot enough range for re-calibration..."
...In rare instances, we run into a tach that will not calibrate with the standard 1k resistor. In those cases, we substitute a 4700 ohm resistor in place of the 1000 ohm unit we typically add. This usually does the trick.

If you have any problems with the above process, feel free to contact us, or you can send your tach to us for the modification (we occasionally have re-cal'd tachs in stock and ready to ship on an exchange basis). We charge $55.00, which includes return shipping (inside the US.) Just mail your tach and a check for $55. to:

Granny's Speed Shop
POB 814
Concrete, WA 98237


Next page....

1....Introduction....

2....Considerations & Requirements....

3....Getting Started....

4....Engine / Transmission Installation....

5....Exhaust / Throttle Cable / Accessory Drive / Pulleys....

6....Cooling / Fuel Systems....

7....RX-7 Wiring Harness Connector ID and Circuit Locations....

8....Electrical System Modifications By Circuit....

9....Start-up / Troubleshooting....

10....Upgrades....