 V8 tach issues, V8 tach |
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| kyracedog |
 Jul 25 2007, 03:56 PM
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#1
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Newbie  Group: Members Posts: 19 Joined: 19-November 05 From: kentucky Member No.: 5,151  |
What has to be done to the stock 914/4 tach to allow using the HEI distributor signal to accurately show engine revs? I have heard adding a resistor, but not clear? Tried a cheap aftermarket tach, worked one day and died. 2nd one never worked. Is there something from the HEI that is unique?
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Replies(1 - 8)
| nick mironov |
Jul 25 2007, 09:15 PM
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#2
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nickm Group: Members Posts: 204 Joined: 12-June 05 From: San Francisco, CA Member No.: 4,264 |
See the following 2 options for converting a 74-75 tachometer. (Earlier tachometers are different - see pdf attachment). Nothing special required with an HEI distributor. I converted two tachometers - one using the resistor method and the other using the capacitor method. Both methods worked. The problem was that both tachometers were crap to begin with - they had no damping and would grossly over-react causing the needle to swing back/forth until it settled down.
I finally gave up and got a tachometer from bigmarkdesign. Very nice. $150. Attached image(s)  Attached File(s) 
Early_Tach_Conversion.PDF ( 141.65k )
Number of downloads: 126 |
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| BIGKAT_83 |
Jul 26 2007, 05:15 AM
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#3
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Senior Member Group: Members Posts: 1,798 Joined: 25-January 03 From: Way down south Bogart,GA Member No.: 194 Region Association: South East States 
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The damping of the 914 VDO tach is not a electrical adjustment. Its set on the back of the meter movement. A small pin is set in silicon grease and dries out over time and causes the swing. Its a pretty easy fix after you have done a couple of them.
Bob |
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| nick mironov |
Jul 26 2007, 01:52 PM
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#4
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nickm Group: Members Posts: 204 Joined: 12-June 05 From: San Francisco, CA Member No.: 4,264 |
What is the procedure for the fix?
Nick |
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| turbo914v8 |
Jul 26 2007, 09:47 PM
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#5
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Member Group: Members Posts: 373 Joined: 26-July 03 From: Canada Member No.: 952 |
I have RH converted tach you can have for 40 + shipping if your interested please PM me. It cost me 100 + at the time.
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| drive-ability |
Jul 27 2007, 12:02 AM
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#6
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Senior Member Group: Members Posts: 1,169 Joined: 18-March 05 From: Orange County, California Member No.: 3,782 |
QUOTE(turbo914v8 @ Jul 26 2007, 08:47 PM)  I have RH converted tach you can have for 40 + shipping if your interested please PM me. It cost me 100 + at the time. Paul PM sent (IMG:style_emoticons/default/biggrin.gif) |
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| BRAVE_HELIOS |
Jul 16 2010, 10:19 AM
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#7
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"Knowledge speaks, wisdom listens" Group: Members Posts: 295 Joined: 25-September 06 From: The Land Of ID! Member No.: 6,920 Region Association: Pacific Northwest |
QUOTE(nick mironov @ Jul 25 2007, 09:15 PM) See the following 2 options for converting a 74-75 tachometer. (Earlier tachometers are different - see pdf attachment). Nothing special required with an HEI distributor. I converted two tachometers - one using the resistor method and the other using the capacitor method. Both methods worked. The problem was that both tachometers were crap to begin with - they had no damping and would grossly over-react causing the needle to swing back/forth until it settled down. I finally gave up and got a tachometer from bigmarkdesign. Very nice. $150. Hope y'all can help! I have a tach dated 9/74… the one with the calibration pot. I want to convert it for v8 use. I am looking in the same area as in your photo. My tach already has 3 resistors mounted on the board! As far as I know this tach came out of a 4 cylinder car. What gives! It does have a 0.22 capacitor in place. Somewhere around this forum, I also saw someone who replaced the 0.22 uf cap with a 0.10 uf cap with the same results. Any thoughts? Thanks! Attached image(s) 
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| joefri187 |
Jul 16 2010, 04:54 PM
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#8
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Newbie Group: Members Posts: 29 Joined: 1-November 05 From: Concord, CA Member No.: 5,047 Region Association: Northern California |
This looks similar to the picture above, but see if this helps...... It worked perfect on mine....
Attached File(s) 
Tach_cal_small.doc ( 73.5k )
Number of downloads: 92 |
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| rick 918-S |
Jul 16 2010, 08:34 PM
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#9
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Hey nice rack! -Celette Group: Members Posts: 20,470 Joined: 30-December 02 From: Now in Superior WI Member No.: 43 Region Association: Northstar Region
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QUOTE(nick mironov @ Jul 25 2007, 10:15 PM) (IMG:style_emoticons/default/agree.gif) Send it to Mark. It's way too easy that way. |
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