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; 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; 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; 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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