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V6 tach or V8 tach

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Old 11-26-2009, 08:44 AM
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Car: 1987 IROC-Z Z28 Convertible
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V6 tach or V8 tach

Is it true a tachometer can be specific for a V6 or V8? Is there a way to change the setting to make it work?
Old 11-26-2009, 08:52 AM
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Re: V6 tach or V8 tach

i know on my 84 z28 i was but on my 92 rs it is ! so yes and no !
just take you tach off and look for a switch that says v6 v8 on the back of the tach !
good luck !
Old 11-26-2009, 11:23 AM
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Re: V6 tach or V8 tach

i would think theres no difference, like a tachometer just measures rpm. 5000 rpm is 5000 rpm, shouldnt matter if its a v6 or a v8
Old 11-26-2009, 11:34 AM
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Re: V6 tach or V8 tach

No difference in the gage, only the marked redline will be 6000 RPM's for a V-6.
Old 11-26-2009, 12:16 PM
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Re: V6 tach or V8 tach

for aftermarket it depends. i had a sunpro tach (cheap$30) that i bought once and it had a switch in the back for 4, 6 or 8 cyl. for stock, i wouldn't think so. the v6 i think gets the signal from the icm and the v8 gets it from the distributor.
Old 11-26-2009, 02:25 PM
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Re: V6 tach or V8 tach

There is a difference. I can't explain why, but i tested mine and there was a couple hundred Rpm difference in between settings.

Besides, If you have a v8, get a v8 tach. Doesn't that just make sense?
Old 11-27-2009, 09:24 AM
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Tach This !


Originally Posted by Sandslot;
Is there a way to change the setting to make it work?
Yes.

A tach lets you know the RPM VIA counting pulses from the ignition system.

An 8 cylinder engine produces 4 pulses per revolution.

A 6 cylinder engine produces 3 pulses per revolution.

A 4 cylinder engine produces 2 pulses per revolution.

Your problem can be remedied in the circuit inside the dash that moves the pointer.

It’s contained on a small plug-in PCB or integrated in the main board.

On the PCB you’ll see a resistor chip.

Desolder pins 4 & 10.

Use a 500K potentiometer.

Solder it across traces 4 & 10.

Move the potentiometer to half way.

Start the engine and compare the tach reading with a test equipment quality tach.

Dial it in, unsolder one side of the potentiometer, measure it and buy the matching resistor.


Originally Posted by sablemaniac;
the V6 i think gets the signal from the icm and the v8 gets it from the distributor.
Be it V6 or V8, the tach gets its’ signal from the distributor COIL PRIMARY.


Happy Racing!



If People Drove Any Slower They’d Be Going Backwards

When you see fog lights on in good weather beware. Low performance driver ahead.

How bout those nervous nellies too scared to drive without headlights on in the daytime or if there is a little rain!

.
.

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