V6 tach but running a V8....

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Caprimaniac
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V6 tach but running a V8....

Post by Caprimaniac » Mon Jun 04, 2018 9:16 am

Hi. Posting here since it does not belong in any other tech- forum.

70’s car, coil- signal tachometer for v6 engine. Is there an easy way to have this i meter to show correct RPM with a v8- engine w/ tach installed?

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RS
How to turn GURU in an instant.....

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Baprace
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Re: V6 tach but running a V8....

Post by Baprace » Mon Jun 04, 2018 8:26 pm

Capri, some early tachometers had a selector setting inside the tach head on the circut board.

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Re: V6 tach but running a V8....

Post by user-23911 » Tue Jun 05, 2018 3:25 am

Factory tach....you want it to read 3/4 of the new reading. You're now getting 4 pulses per rev when you were getting 3 per rev before.
That means you want 3/4 of the current to now flow through the meter movement.

If for example the mechanism (meter movement) measures 1000 ohms, add a parallel resistor of 3000 ohms.
3/4 of the total current will now flow through the meter, 1/4 through the resistor.
The new combined resistance has now dropped which might upset the circuit.
1000 ohms in parallel with 3000 ohms makes 750 ohms. Adding a 250 ohm resistor in series should correct everything.

I went through this a few years ago. It even worked.

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Re: V6 tach but running a V8....

Post by Caprimaniac » Tue Jun 05, 2018 9:45 am

Wow, gents. What should.a simple man like me do without help from you ST- guys.

I will check for any adjusrability, but doubt so since the gauges for 4- cyls had a different part no and rhe car never came with a v8.

I’ll purchase this oe kit of GT- gauges/ dash then, and see if I manage to convert my»racer» into a morr propper GT- car. Will have fun getting the readings right...

Thank you.
RS
How to turn GURU in an instant.....

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