Speedometer Restoration

[Timothy B.]

I wanted to post and thank the person that took the time to write the article on speedometer restoration in the latest Corvette Restorer Magazine.

All the articles are very good and interesting but the speedometer on my 67 needs work and this article helped me to visualize what the problems could be.

Great Restorer Magazine this month..

[Ken A.]

Re: Speedometer Restoration

I would take all the 'tips" & "secrets" with a grain of salt, as they say.

[Domenic T.]

Re: Speedometer Restoration

Tim,
Talked to a guy that does them that moved here in Palm springs from the east. He seemed to know his stuff. He chimed in and posted once about the speed warning. I forget how we ended up talking but he also had hard to get parts and does cluster restoration. I could not find a part for my 67 speedo and sent it to somewhere in Ohio I think. My speed warning gave me a problem and he gave me some good advice and said if it were out to let him check it.
Any way he sounded like a goos possibility. His name is Brian (760) 568-6450.

Dom

[Rick A.]

Re: Speedometer Restoration

Yepper, Brian used to be here in Maryland, and Tim knows him well. Another possibliity is Rick Stotler who is Brian's brother-in-law and is in Joppa, MD.

[Stuart F.]

Re: Speedometer Restoration

I replaced an odometer gear many many years ago and my unit continues to work well some 40+years and miles later. Although mine is a 63, and time blurs the memory, I read the article thoroughly and I can't say it looked all that familiar. I recall only that I opened the unit up, saw the bad gear, and replaced it without much trouble. I will say my speedometer reads about 5 MPH too low, but I convinced myself it was the change in tire size. Then, I never paid too much attention to it anyway. I just either keep up with traffic or get some distance between them and my gas tank.

Stu Fox

[Richard F.]

Re: Speedometer Restoration

Maybe you guys all know this already, but I'll put it out here anyway. There is a laser device that comes with stickons that you put on something that rotates, in my case an electric drill chuck. I clamped the speedo cable in the drill, pointed the laser at the stickon, and spun the drill up until the laser said "1000RPM" and happily noted the speedo was reading 60MPH. Haven't found another use for the laser, but it was sure great that one time.

[Mike E.]

Re: Speedometer Restoration

Maybe you guys all know this already, but I'll put it out here anyway. There is a laser device that comes with stickons that you put on something that rotates, in my case an electric drill chuck. I clamped the speedo cable in the drill, pointed the laser at the stickon, and spun the drill up until the laser said "1000RPM" and happily noted the speedo was reading 60MPH. Haven't found another use for the laser, but it was sure great that one time.

Oh but you could say it was calibrated with a laser. How cool is that?

Mike

[Stuart F.]

Re: Speedometer Restoration

Calibration, calibration! What's that all about? I live with a Vette that reads 5 mph too low and a Rabbit that reads 5 mph too high! I just keep up with traffic most the time and don't worry about it. Here in Orlando every body speeds and runs red lights. The challenge is spotting the intersections with those darn cameras. Got caught turning left behind a semi once - ouch!

Stu Fox

[Timothy B.]

Re: Speedometer Restoration

Calibration, calibration! What's that all about? I live with a Vette that reads 5 mph too low and a Rabbit that reads 5 mph too high! I just keep up with traffic most the time and don't worry about it. Here in Orlando every body speeds and runs red lights. The challenge is spotting the intersections with those darn cameras. Got caught turning left behind a semi once - ouch!

Stu Fox

Stu,

Just put the tires from the Rabbit on the Corvette and it will be fine. :-) OH, and no running red lights with the Corvette..

[Stuart F.]

Re: Speedometer Restoration

Thought of that. Wrong bolt pattern.

Stu Fox

[Mike E.]

Re: Speedometer Restoration

The challenge is spotting the intersections with those darn cameras. Got caught turning left behind a semi once - ouch!

Stu Fox

Ahh...but that's why they have these.

http://www.amazon.com/Escort-Passpor.../dp/B001F0RPGG

It has a GPS with a database that warns you about those. But I agree...It's never a good idea to run a red light....Period! Stu was saying he got stuck behind a truck and didn't know it was there...I could see how that could happen.

I don't really speed that much in the Corvette...The speed can just creep up on you sometimes.

Mike

[Stuart F.]

Re: Speedometer Restoration

Mike, Will that unit spot the red light cameras? That's my main concern here. You have to be alert for the posted warning signs (very small), and the camera boxes. They are usually used in places with short left turn lanes and very short green, yellow, red arrow lights. They are pure money makers run by contractors who probably get paid a percentage and having an iron clad contract that ties the cities hands. They have been found to be illegal in some states.

Since I got caught that once ($158.00) I now use a special license plate frame/cover that blurs the camera view of my rear plate, yet lets the human eye see it ok. Just a little smoke and mirrors trick I learned back in the old days. So far so good, but I do try hard to abide by the law too.

Stu Fox

[Mike E.]

Re: Speedometer Restoration

Stuart,
This video explains how the device works.

Mike

[Stuart F.]

Re: Speedometer Restoration

Mike;

Thanks. That looks like quite the device. I'll look into it. Guess I can pitch my old ones now - except for the mounts. Small suction cups don't work too well here in Florida unless the unit is real light. I have a Transponder for the tollways that has the cups (although the stick on patches are available) because I often move it from car to car. It is real light and I have left in one car for days. I'm sure, due to it's value, one wouldn't want to leave it in the car.

Thanks again.

Stu Fox

[Lynn H.]

Re: Speedometer Restoration

I have not been on the site in some time, but felt "COMPELLED" to comment on the speedo article in the latest Restorer. While I can appreciate the time and effort put into this article by a fellow member, it has been on my mind since I seen it. I would like to say that anyone heading down this road with this article for a reference is in serious trouble, and headed the the "speedo shop" for the high dollar repair.
There is so much erroneous information in this article as far as speedo repair and function, that if you happened to get anything close to accurate it would be by "mistake". I truly intend no disrespect for someones effort. Finding information on how to repair AND CALIBRATE a mechanical speedo and tach, proved to be a long quest for me to get it right, that took many many months. It "ain't rocket science", but it does require a certain process for the instrument to be calibrated and function properly.
I would be more than happy to explain to anyone seriously interested who does not know if they wanted. A couple of things off the bat for the restorer:
If the "field plate" is removed from the assembly, the unit MUST be recharged and calibrated, and this MUST be done as an assembly.
You CANNOT charge the magnet with the proper result as instructed in the article.

then: there are some things that come into play (you do not want to have to take the dash in and out more than once)

A GOOD fully charged magnet should have a minimum of 50% overcharge at 60mph. Meaning once charged as an assembly and assembled as either a speedo or tach, it has to say 90 mph when the master calibration device is at 60 mph (50% over). If you cannot get close to this the magnet is deemed "defective".
The magnet MUST be charged with DC current.

Then the "unit" assembled you must DISCHARGE THE MAGNET with AC current to bring it into a range where you can then use the "fine" adjustment.

As far as repairing the "odometer" issue which was the basis of the article, I would offer one bit of advice for diagnosis if you attempt this. The biggest problem is not that the " first worm" (on the magnet) goes bad. The bushing and or housing that the magnet shaft runs in wears out. This causes the "second worm" to lose engagement with the first gear. Just replacing the second worm is a recipe for disaster, as it will soon have the same "groove" in it, without a new "frame and magnet assembly".

With all due respect to the anonymous author, This article is going to cause serious problems for anyone attempting in this manner.

Lynn Houk 28522