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Discussion Starter · #1 ·
Tachometer question

This is for those of you who have converted to a v-6 or v-8 engine. How do you make the original tachometer for a GT work with the "new" engine?:confused:
 

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That is a question I posted on both this site and the other major Opel site. There was someone, somewhere that had, or was building a schematic or circuit board that would replace the original tach board with a one that would work with the V-6. I had his e-mail address but somehow it vanished in my e-mail list. If anyone has the answer to this question, a response would be appreciated.

Ron
 

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boomerang opeler
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use any tach for the number of cylinders you have with the same size pin for the pointer
open up the opel tach and remove pointer (arm/needle)
then strip out the mechanisim
do same for new tach and mount in opel can (alter conections to fit) if orig and new mounting points for face do not match then use epoxy to mount face when dry add pointer glass and reclamp bezel
remount in dash :D
 

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Baz, that would only work if the donor tach board has the same needle sweep as the opel, ie. 270 degrees. The tach needle sweep on the Firebird instrument panel I got to run the engine on the stand is less than 180 degrees, so it wouldn't work. I know there's someone that was working on a board mod. I just don't remember who.

Ron
 

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boomerang opeler
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ron im blessed with a country full of cars with 270 deg tachs so it works for me all the time:D
 

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I may have to check out local recyclers and see what I can find. Thanx Baz, as usual, my brain isn't in gear so early in the morning.

Ron
 

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why not find out what makes aftermarket adjustable and install something to be able to change the signal
im betting there is a resistor of some type
 

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you could go digital. then let's say you went from 4cyl to 8 cyl your pulse counting circuit would read twice as high. Offset that by sampling pulses and t/2 and you get the same RPM. Or revolutions per second times some multiplyer.
TMT: too much trouble, though. alas.
 

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Well, if push comes to shove, I've got a really old RadShack digital clock and tach, with a headlight on warning circuit I could plug in to see what's going on in the engine, but it's hooked up to my van right now. It has settings for 4 - 6- 8 cylinders, and is a small box about 4 X 2 X 3" ,with 4 1/2" red L E D digital readouts. I had thought of using it before, but I would like to keep the original dash configuration right now.

Ron
 

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6-cylinder Opels

Just a thought. Do any of the six-cylinder Opel Commodores or such of the 1970's use a similar VDO tach? Do any German sixes of that era? Maybe Baz can help with those answers!
 

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How about a cheap and easy fix? Take the guts out of this particular item. You will find two wires in and two to the meter itself. Clip them all and hook the board in between your coil and your tach. flip switch to 6 cylinder and be done with it. It also has pots to tune it in. I opened up mine just to see if it would work. I hope to never need a dwell meter again so opening it didn't hurt my feelings. It also has a switch for dwell and tach function. New on Ebay is 10 bucks but even that seems a bit high.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=43989&item=2457982174
 

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Noboby, that meter has about a 120 degree swing, I don't think it will work in a 270 degree tach. JMTCW.

Ron
 

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Discussion Starter · #14 ·
Going digital sounds like a easy idea but I would like to continue to be able to use the original tach. What has everyone who changed to a V-6 done with the original tach?
 

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The meter part of it goes in the trash. All you want is the board to be able to convert your 6 cylinder signal into something usable for the stock tach. Now that I think of it you would need to bypass any electronics in the stock tach. What this board is doing is changing the hertz of your rpm to millivolt so it can be displayed on an analog type of meter.Both sets of electronics do this now, but at a different ratio. The idea is to use the meter on the stock tach and the electronics that drive the other one. Any difference in millivolt max for say 7000 rpm can be adjusted by the pots on this particular board. After all the stock tach is just an analog millivolt guage, just swings a bit more and is mounted the way you want.
 

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boomerang opeler
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nobody
i dont think that meter would be able to work a tach ,i doubt it could take the power to move the works in a tach:(

ron that meter only sweeps about 45 deg time for more coffee:D

jim have had a look through a few sites but could not see any comm clocks but theres always holden/vauxhall/opel, VW,BMW,mercs,ford all have 6 cylinder modles with tachs and if they are european origin then chances are they are VDO

its all right for you's i've got to get mine to work for a V12
must get on with that soon jags in the garage to strip just cant be arsed right now still only an hour to change when i do get it out wireing is another mater though :confused:
and to all its only hard till you try or if you play with it!!!!
 

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boomerang opeler
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this is a ford european 1 i used in my gt (6 cyl)
 

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That may be the way I'll have to go. Find a 270 degree tach out of a V-6 in the auto cycler's yard and remove it, then try to get the board in the Opel's housing and hook up the pointer and face so everything works as advertised. More stuff to do. One step forward, two back. :rolleyes:

Ron
 

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Who Ya Gonna Call!

Try:

VDO Instruments
188 Brooke Road
P O Box 2897
Winchester
VA 22603
U.S.A.

Phone: 540-665-2428

They might know a bit about VDO tachometers:D
 
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