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  #1 (permalink)  
Old 03-29-2005, 11:48 AM
1985 CCX's Avatar
CSX2375R Comp289
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Default Speedo

Help?

Any ideas how I can make my speedometer more accurate. At 70 my speedo measures high by ~20mph. Smiths 180mph gauge with TopLoader.

Thanks
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Old 03-29-2005, 01:04 PM
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Your speedometer is actually a voltmeter. It simply reads the voltage generated from the small generator inside it that the cable is driving. There is a calibration screw on the back (it might be touched with a dob of paint). You have the right idea already, if you can get an accurate difference at highway speed, lets say your number was 90 and supposed to read 70. You can remove the speedo and put it on a drive like a variable speed drill and bring it up to 90. You can use a universal speedo cable or the one from the car to drive it. Now turn the adjustment calibration screw on the back to make it read 70 and you will be pretty close. The other more expensive option is to have it calibrated on a machine like a dyno or rolling road machine that effectively does the same thing only by spinning the wheels through the drivetrain to get the speed and giving the same screw a tweak.
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Old 03-29-2005, 01:13 PM
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Default You gotta be kidding!!!!?????

"It simply reads the voltage generated from the small generator inside it that the cable is driving."

A small generator inside the speedometer?????? Wha?????


My fuel gauge measures total fuel weight, and density relative to the barometric pressure for the day. It then factors in the coreolas effect as the fuel empties down the fuel line and calculates the remaining fuel in the tank which it posts to my old analog gauge.

Sorry, I had to do it!

Ed
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Last edited by CobraEd; 03-29-2005 at 01:21 PM..
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Old 03-29-2005, 01:27 PM
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Default Re: Speedo

Quote:
Originally posted by 1985 CCX


Help?

Any ideas how I can make my speedometer more accurate. At 70 my speedo measures high by ~20mph. Smiths 180mph gauge with TopLoader.

Thanks
CCX? Is that a Contemporary? If so, you'll have to change the speedometer driven gear at the transmission end of the cable.
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Old 03-29-2005, 01:50 PM
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Now there's an easy fix! Thanks Bob, and you know CCX is Contemporary. Nice looking car BTW.
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Old 03-29-2005, 03:05 PM
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Thanks

Yes CCX does indicate Contemporary Classic. Thanks for the compliment mickmate! Any ideas where to get a gear replacement and procedure for determining the correct gear if there is no adjustment screw?
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Old 03-29-2005, 05:14 PM
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David Kee is the toploader man on this site, his link is on the left of the page and he can advise on correct gear also I bet.
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Old 03-30-2005, 10:17 AM
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Mickmate,

Looked last night and there is a screw on the backside lower portion of the speedo. It actually sets out ~1/8th" and has a green washer between it and the speedo housing. Would you agree that this may be an adjustment point? How much of a turn would it take, have you done this? Want to make sure I do not destroy the unit.

Thanks
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Old 03-30-2005, 11:04 AM
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Yes I have done this and it worked quite well. Did you look into different gears? I'm guessing that would be a simple proportioning problem. 70/90 = .777. A 14 tooth gear X .777 = 10.88 so you'd use an 11 tooth gear if you could get one. Try turning the screw but make a note of where it started, both on screw position and needle reading. There are a few good articles from a google search on speedometer calibration and adjustments depending on the principle. Some of us aren't afraid of finding out how things work and tinkering with them a little, go for it (in a methodical way of course). Let us know how it works out.
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