Need the V8 tach modification "How to", Searched and came up with no details.. Options

[Dr. Roger]

Looking for details on the V8 tach modification.

A "how to" and a pic would be awesome. Maybe even borderline stupendous.

=)

On a side note:
I hooked up my ancient speedo tonight and an interesting thing happened. At 15 MPH it read 30. At 60 it went to 100. Then got stuck at 30 and never moved from there. I guess it's due for a tune-up/cleaning. So in the mean time I have a 911 gauge I'll install tomorrow morning and try it out. Hookup looks exactly the same.

Still need that tach mod though. (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/happy11.gif)


Peace,
Roger

[mightyohm]

one way to do it:
(scroll down)
http://www.914world.com/bbs2/index.php?sho...p;hl=tach++face

[brer]

I have a VDO tach for an 8 cyl. if you find the need for one.
cheap.

(IMG:style_emoticons/default/smile.gif)

[rick 918-S]

Here ya go! Contact Mark (Marks914) He'll do what ever you like.

http://www.914world.com/bbs2/index.php?sho...c=72389&hl=

[marks914]

Send it to me, I will not only make it into a V8 tach, but it gets fully refurbished and a redline of whatever style and placement you want
only $150

Mark

(IMG:http://inlinethumb53.webshots.com/41012/2001892860057582025S600x600Q85.jpg)

(IMG:http://inlinethumb02.webshots.com/28353/2851033840057582025S600x600Q85.jpg)

(IMG:http://inlinethumb44.webshots.com/42603/2179585910057582025S600x600Q85.jpg)

(IMG:http://inlinethumb46.webshots.com/23149/2570480490057582025S600x600Q85.jpg)

[Dr. Roger]

Thank you all,

I am really just looking for the tach modification. If that doesn't work out I will probably be going to eitherMarks product or a creation of my own. =)


(IMG:style_emoticons/default/chowtime.gif)

[cobra94563]

(IMG:style_emoticons/default/popcorn[1].gif)
(I could use that tach mod as well, if anyone has the info.)

Right now using a autometer that fits in fine, but wouldn't mine the stock unit.

Also, if there is an adjustment screw on the speedometer anyone knows of?

[Dr. Roger]

Bob B. (BIGKAT_83) is the author of this solution.

This is the newer style 914 tachometer with the single turn signal indicator light. You can calibrate this for a V8 engine by adding a 15k ohm resistor in parallel with the existing 15k ohm resistor. This then gives you enough adjustment with the pot to calibrate this for the V8. Before I put the tach back together, I wired the tachometer up with jumpers and adjusted pot with the engine running and compared to another (auto meter) tach.

The older style tachometer with the dual turn signal indicator lights has a different calibration board. There is not an adjustment pot for it. I’ve got an extra early tach in working order and the first chance I get I’m going to try to recalibrate it.


Thank you Bob!

(IMG:style_emoticons/default/aktion035.gif) (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/smilie_pokal.gif)

[BRAVE_HELIOS]

Bob B. (BIGKAT_83) is the author of this solution.

This is the newer style 914 tachometer with the single turn signal indicator light. You can calibrate this for a V8 engine by adding a 15k ohm resistor in parallel with the existing 15k ohm resistor. This then gives you enough adjustment with the pot to calibrate this for the V8. Before I put the tach back together, I wired the tachometer up with jumpers and adjusted pot with the engine running and compared to another (auto meter) tach.

The older style tachometer with the dual turn signal indicator lights has a different calibration board. There is not an adjustment pot for it. I’ve got an extra early tach in working order and the first chance I get I’m going to try to recalibrate it.


Thank you Bob!

(IMG:style_emoticons/default/aktion035.gif) (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/piratenanner.gif) (IMG:style_emoticons/default/smilie_pokal.gif)

Resurrecting an old thread… Okay, so 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 (see foto)! 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. Also, I can figure out how to replace one cap with another, but please explain/show how to run one resistor parallel with another!! Any thoughts?
Thanks! (IMG:style_emoticons/default/driving.gif)

[roadster fan]

the gauge you have pictured is not the later style that Dr. Roger refers to. The 1975 and 1976 tach has one indicator light for the turn signal and the needle is different. The pic below is the gauge he is using i believe. Your tach may be a transition year old style with adj. pot, but no really sure.

If you look closely the layout of the two circuit boards is different with different components.

[BRAVE_HELIOS]

the gauge you have pictured is not the later style that Dr. Roger refers to. The 1975 and 1976 tach has one indicator light for the turn signal and the needle is different. The pic below is the gauge he is using i believe. Your tach may be a transition year old style with adj. pot, but no really sure.

If you look closely the layout of the two circuit boards is different with different components.

Good catch! I should have explained further. My car is a '71, and has white faced gauges (which I like). I had a '74 tach laying around, so I decided to swap. What you see is the '74 innards mounted to the '71 face.

There may have been transition models; but I am unsure. What I know is that the '71 mechanism has no calibration pot, while the '74 does. I've been trying to fine out why the tach I have looks slighty different than the other late style innards. As always, more information is needed!