North American Turbocoupe Organization



140mph conversion kit (not the white face one)
BradM Offline
Member
#1
Has anyone installed the black face 140mph speedometer conversion kit? This is not the white overlay sticker. The black face kit requires you to remove the old face and solder in some new components to recalibrate the speedometer.

whitegauges.net

1985-1988 Ford Thunderbird 140 MPH Motorsports Replacement Face Speedometer Conversion
http://www.whitegauges.net/products/1985...rsion.html

Instructions
http://www.whitegauges.net/product_image...d_2579.gif
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1982 Mustang; 1987 Thunderbird Turbo Coupe; 2017 Police Interceptor
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Chas K 88 Offline
Member
#2
I have not. Years ago I was looking into a 140 speedometer and there was a write-up here about doing it yourself. I can't swear to it but I think it was Jeff Korn who wrote it. Seems like there was some equipment needed to calibrate it (frequency generator, maybe) that I didn't have on hand, I said it was years ago.  Long story short, Jeff & I got to talking and I ended up sending mine to him and he did it for me for not a whole lot of cash. Now, I'm not volunteering him to do yours but you may want to contact him about it, the man is a wealth of information.
Chas K
Current setup - 88 T-bird, 5 speed, vacuum assist master cylinder, T3/T4 50 trim turbo from Bo-port, oil feed & return lines, 3” turbo down elbow, 3" to 2.5" dual exhaust and PiMPx from Stinger 255LPH fuel pump, CD, trip-minder, RR , K&N, 140 MPH speedo conversion (thanks Jeff K).
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Jeff K Offline
Administrator
#3
As Chas K said, Years ago I used to do 140 conversions plus calibrate the converted speedos so they were accurate to within 2 mph over the entire speed range. I think I charged $80 for the service plus shipping costs both ways. The hardest part was the calibration, which took 75% of the total time. I got out of the business 10+ years ago after doing around 30 conversions as "life got in the way".

It is a very simple process to do the electrical conversion if you have reasonable soldering skills. Even without the calibration I would do, most turned out to be pretty accurate without much adjustment. Calibration just required a sine wave frequency generator. the transfer function is 2.22 Hz per MPH. In other words, 220 Hz input to speedo = indicated 100 MPH.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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BradM Offline
Member
#4
Thanks Chas and Jeff. By calibration, do you mean swapping in different resistors or adjusting a pot?
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1982 Mustang; 1987 Thunderbird Turbo Coupe; 2017 Police Interceptor
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Jeff K Offline
Administrator
#5
When I did the calibrations I started out being sure the needle was right at the zero speed peg. I never changed / adjusted the resistor and/or capacitor values. I would always check the resistor and cap values with my Fluke DMM to be sure they were very close to the specified value.

I discovered that the calibration changed depending on the angle the speedometer was sitting at, so I would set the speedo so it was at the same angle as when installed in the car.

I then used my signal generator (sine wave, a couple volts peak to peak) to check calibration every 10 MPH from 10 t0 140 MPH. I verified the signal generator output frequency with my Fluke DMM.

The fun (NOT) part was getting the calibration correct across the entire speed range. Sometimes calibration was fine, other times not. If it wasnt accurate across the entire speed range the following PITA method was used: There are 2 copper / brass tangs opposite each other on the speedo needle shaft with little sliding weights on the tangs. Adjusting the sliding weights and rechecking calibration eventually getting the +/- 2 MPH accuracy across the entire speed range.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
11 Crown Vic Interceptor
14 Toyota Camry (wifes car)
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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BradM Offline
Member
#6
Oh lord. This sounds like tuning a watch. Good insight. Thanks.
1965 Mercury Comet Caliente; 1968 Mercury Monterey; 1969 F100 Ranger; 1982 Mustang; 1987 Thunderbird Turbo Coupe; 2017 Police Interceptor
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spittinfire Offline
Member
#7
I've thought about putting one of these in my car but I've read about some people having issues with accuracy after the install which made me hesitant. If I can pick up a signal generator cheap enough I might give it a try. I've got a spare speedo or two I could play with to figure things out.
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teal95 Offline
Senior Member
#8
I would guess there is a way to use the sound card in your computer to make the signal.

steve
'83 & '84 GT turbo EEC-Tuner
'85.5 & '86 SVO twEECer
2x '87 & '88 TC QuarterHorse
'93 LX 5.0 notch Moates chips
3x '95 & '96 GT
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anasazi4st Offline
Senior Member
#9
(04-05-2022, 09:11 PM)teal95 Wrote: I would guess there is a way to use the sound card in your computer to make the signal.

steve

I'm in the process of this modification for my TC. I found several sets of instructions which have been very helpful--the more on this I can find the better. (Jeff's instructions above are amongst the best I've found.)

Some are no longer available--you get ERROR 404. I know Chip (biggrgivens--Big R Motorsports) had posted photos on TurboFord.com and Photobucket on this as he was involved in it for a while--and I had saved those links--but now, again, ERROR 404. (If anyone has a way to contact him please ask if he could re-post his information and photos again somewhere.)

Meanwhile we have this, from the CoolCats.com website (Mercury Cougars): https://web.archive.org/web/201708152044...peedo.html . Note that the original post is unavailable--this is from the Wayback Machine.

Also this, from the FAQ section right here on NATO: https://turbotbird.com/thread-speedo-cal...ght=140mph .

I've already modified one stock 85mph speedometer. I replaced the indicated capacitor and followed the instructions on the CoolCats site to prepare the faceplate for the new 140mph face, which I printed from the Downloads section on vinyl adhesive backed paper. I went through several copies before I was satisfied enough with the results of cutting out the small boxes for the odometer (and so on--you need great patience, a steady hand, and a VERY sharp razor knife). I got it within 2mph +/- accuracy throughout the speed range.

You'll need a 12 volt power source for the speedometer. I used this one from Amazon, which has adjustable voltage so I can use it for other projects. (You might have to sign in to your own account.) https://www.amazon.com/dp/B0B88V1YWC?ref...tails&th=1 

As for the signal generator--I purchased several on Amazon and was unhappy with each, for various reasons, the most common one being you could only input/utilize whole integers, which doesn't work (for example, the sine wave frequency for 70mph is 155.5555554). I've also looked for signal/tone generator software for both Mac and PC. Again, the biggest drawbacks are 1) cost--I'm not interested in paying $200 for software that I'm not going to use after this project is completed; 2) only 2 decimal places--I'm not sure how many places you'd need for absolute accuracy, but the more the better I would think; 3) inability to save the various speed settings--I'm not happy with the idea of typing in the numbers over and over again.

If you use a Mac or PC the best choice so far seems to be Audacity, which is open source, free, and allows you to save each setting so all you have to do is click on each to reload. It's meant primarily as sound recording software, but is capable of generating a SINE wave tone which is output through the computer's Headphone port. Audacity's major drawback is that it only allows 2 decimal places in the outputted result, which again may or not be important. (I used Audacity to calibrate the first speedometer, which seemed to work ok.) There are versions for just about any Mac or Windows version no matter how old.

I didn't find software for Windows that I was as happy with as Audacity (on the Mac). Most have trial versions that are lacking features and have some or all of the problems I mentioned above.

One last note, and I don't want to sound negative, but it's probably best to avoid the "white faceplate" place that sells the 140mph conversion kit. They do offer a nice professionally printed plastic faceplate and the electronic components you'll need to convert the speedometer--but it doesn't work and more modifications are required, like moving the tiny weights inside the thing. When I contacted them about the poor accuracy (before I knew that I had to do more work than just soldering in the parts), they seemed surprised that it DIDN'T work as advertised and said they would work on it in their shop to find a solution. After a few months eventually they gave up and refunded my money. $89 seems a lot to pay for a capacitor you can get 100 or so on Amazon for under $10. You can print the faceplate yourself, and while it's not as professional as what they offer I'm still not sure it's worth $89. (They also provide you with some resistors to solder inline with a couple of the existing ones, but they don't seem to make that much of a difference and are also available elsewhere much cheaper.)
Another proud dues-paying member.

1987 Turbo Coupe w/T5OD, 8.8 axle, grey smoke; most options. Got it in 1991 with 41K miles: 3 turbos, 2 heater cores, 3 T5OD full rebuilds, 6 clutches, 1 head gasket, 2 Teves II ABS units, etc. later....
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spittinfire Offline
Member
#10
How do you get the needle off? I'd love to blend an 86 and 88 tach but I can't get the needle off.
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