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For those doing Ford 302 or 5.0 swaps - Gauge info.


helrazr70
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I am going to post new threads on all the individual obstacles as I go and eventually I will create a complete "how to" thread on the 5.0/302 swap. I think too many folks are intimidated by V8 swaps. It isn't as hard as it looks and if the info is out there, more people may be willing to try it rather than junk their cars as I have seen happen on more than one occasion.

 

Here goes!

 

The speedometer:

 

The speedometer cable from an '86 Mustang GT with a T5 or auto trans can be used. The speedo end is compatible with the Mitsu speedo head and the trans end fits the transmission speed sensor. To make the speedo read the correct mph all you have to do is buy the correct plastic recalibration gear (black or white one depending on sensor teeth and manual vs. auto trans) for the speed sensor.

 

(3.55 recal gear needed since our cars come with 3.54:1 diff gears)

 

http://www.steeda.com/products/speedometer...ation_gears.php

 

I also discovered that you can disassemble a 79-86 Mustang instrument cluster and with some custom fabbing the gauges will all fit in the SQ housing and are VERY similar in size. You would have to wire them individually and create a back board to mount them.

 

The tachometer:

 

Try to find an instrument cluster from a 79-86 Mustang, Fairmont, Zephyr, or Capri.

 

You will notice that there is a small hole on the ear of the tach housing that has 4, 6, and 8 embossed around it. The 4, 6, and 8 represent the number of cylinders the tach is calibrated for. Inside that hole is a slotted head screw that turns to point at your number of cylinders. Set it to "8". You can use a tach from any 4, 6, or 8cyl car. The tach circuit board is all you need from the cluster.

 

I have noticed that some V8 clusters do not have the selector and are set to be used on V8 only. You can tell a V8 cluster by the fact is has a 7k rpm tach instead of 6k rpm. (and may be missing the cylinder selector)

 

Now, take the cluster apart and remove the tach. Flip the tach over and you will see a circuit board held on with one screw and it has 2 wires (red and black). Remove that screw and cut the 2 wires near the tach leaving the most wire attached to the board. Your SQ tach also has a board with 2 wires--red and black. You can stuff the now board inside the SQ cluster or you can extend the wiring and leave it out of the cluster, but make sure you connect the red wire to the red wire and the black wire to the black wire. You will now have to connect the wires to the new board--the same way the old board was attached to the printed circuit. Follow the circuit and determine witch wires correspond to the tach and connect them. Basically red is power, black is ground, and yellow is signal.

 

According the the '88 SQ wiring diagram Page 8-143, on the cluster harness thats attached to the back of the housing:

 

Tach ground= Black *this wire grounds all gauges in cluster*

Tach power=Blue/Red *this wire supplies power to all gauges in cluster*

Tach signal=White/Black *comes off negative (-)post on coil*

 

It's pretty self explanatory when you have the parts in front of you. I will work on getting pics up.

 

There is another way to do this that involves resistors and/or potentiometers to change the signal and calibrate the tach. I am not sure which resistor needs to be reduced. I am an idea, but 100% sure at this point.

 

The gas gauge:

 

No action needed. The swap does not involve touching that part of the wiring harness. It will work as it always has if you do not disturb any of it's wiring.

 

If you must know, the fuel gauge signal wire is the Yellow/Black wire in the harness on the back of the cluster.

 

The water temperature gauge:

 

Run a separate wire from the Ford temp sender on the intake to the factory harness connector or wire. I believe they use the same resistance values. ...or if you want to be sure, Summit racing offers adapter fittings to install metric sensors into fractional threaded holes.

 

According the the '88 SQ wiring diagram Page 8-143, on the cluster harness thats attached to the back of the housing:

 

Temp gauge signal= Yellow/Green *There are 2 Y/G wires in connector--this one is on the bottom row 3rd pin from right*

 

The oil pressure gauge:

 

Run a wire from the oil pressure sender to the factory harness connector for the factory oil pressure sender. Once again, I think they have the same resistance values and fucntion the same. ...or again, Summit Racing sells oil pressure sender adapters for fractional to meteric threaded sensors.

 

According the the '88 SQ wiring diagram Page 8-143, on the cluster harness thats attached to the back of the housing:

 

Oil pressure signal= Yellow wire

 

The voltage gauge (amperage meter/ammeter):

 

If you connect the alternator to the factory wiring harness just as the factory alternator was connected, the voltage gauge will read correctly, because let's face it--Ford voltage is the same as Mitsubishi voltage! :)

 

The voltage gauge takes it's reading from inside the cluster between the Yellow/Green and Black wires for power and ground.

 

 

I will try to post some pics soon. I will also try to add a few wire colors for reference.

Edited by helrazr70
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  • 8 months later...

<b>The tachometer:</b>

 

Try to find an instrument cluster from a 79-86 Mustang, Fairmont, Zephyr, or Capri.

 

You will notice that there is a small hole on the ear of the tach housing that has 4, 6, and 8 embossed around it. The 4, 6, and 8 represent the number of cylinders the tach is calibrated for. Inside that hole is a slotted head screw that turns to point at your number of cylinders. Set it to "8". You can use a tach from any 4, 6, or 8cyl car. The tach circuit board is all you need from the cluster.

 

I have noticed that some V8 clusters do not have the selector and are set to be used on V8 only. You can tell a V8 cluster by the fact is has a 7k rpm tach instead of 6k rpm. (and may be missing the cylinder selector)

 

Now, take the cluster apart and remove the tach. Flip the tach over and you will see a circuit board held on with one screw and it has 2 wires (red and black). Remove that screw and cut the 2 wires near the tach leaving the most wire attached to the board. Your SQ tach also has a board with 2 wires--red and black. You can stuff the now board inside the SQ cluster or you can extend the wiring and leave it out of the cluster, but make sure you connect the red wire to the red wire and the black wire to the black wire. You will now have to connect the wires to the new board--the same way the old board was attached to the printed circuit. Follow the circuit and determine witch wires correspond to the tach and connect them. Basically red is power, black is ground, and yellow is signal.

 

According the the '88 SQ wiring diagram Page 8-143, on the cluster harness thats attached to the back of the housing:

 

Tach ground= Black *this wire grounds all gauges in cluster*

Tach power=Blue/Red *this wire supplies power to all gauges in cluster*

Tach signal=White/Black *comes off negative (-)post on coil*

 

It's pretty self explanatory when you have the parts in front of you. I will work on getting pics up.

 

There is another way to do this that involves resistors and/or potentiometers to change the signal and calibrate the tach. I am not sure which resistor needs to be reduced. I am an idea, but 100% sure at this point.

 

Do you know if you still need the High voltage spike to run the tach after changing the board. I wanted to eliminate the 8920 tach adapter.

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I don't think you will need the adapter since the Mustang tach runs off the - side of the coil with no adapters. Keep you adapter just in case and use it only if needed. I doubt you will need it.

 

I no longer have all my notes and reference materials since I sold my car...

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  • 4 years later...
I bought a conversion box that will allow the stock tach to work with any engine combination. It has switches you set for converting v8 engine to 4 cyl tach. It goes up to v12 engines but who will ever do that!!! lol anyway it is a universal converter that just bolts up to the firewall. I have it on my 88 with a 351w engine.
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  • 2 months later...
  • 4 months later...
nice writeup and thanks! im a little confused about the battery/volt wire. which wire do I splice into on the cluster harness to run to my alt/batt? you stated its the yellow/green and black but isn't that the water temp wire? I only have one yellow/ green wire on my 88. thanks.
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  • 4 months later...
The Dakota digital will work with our stock tachs for 6,8,10, or 12 cyl engines. Just go by instructions to flip the dip switches for engine/tach combination required. Edited by 88351wtsi
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  • 2 weeks later...
I am using a stock ford ignition box and coil. The Dakota digital box is fed by 4 wires: ground, - coil, + coil and a red wire that if I remember correctly comes from 12v + from ignition box. Don't take my word for it the box came with instructions but that was about 10 years ago.
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I looked up them.there are a couple models of interface. The one you listed was for diesel alternator to tach interface. I'm going to call Dakota and find the one they suggest. Thanks for chiming in. I almost scrapped the idea.and was heading toward building a new cluster
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