I've got a 91 Camaro RS, with a swap from the 3.1 liter to a 5.7 liter. I know the tach doesn't read right, and I know why. The tach is receiving two more signals per rotation than it should giving a false reading, due to the extra cylinders. What I want to know is, is there a connector on the back of the tach that allows you to switch it from the 6 cylinder to 8 cylinder?

I've been told by someone not too reliable that there is, but I wanted to check before cracking open the entire dash to find out. I would get an Autometer tach, but I'm on a budget, considering I recently got engaged.

Any help would be greatly appreciated

 

First off, congratulations on getting engaged. Now, for the tach. Aftermarket Tachs have a 4-6-8 switch, but the stock GMs do not. You would have to get a gauge cluster out of a 305 RS or a Z28. The autometer is nice, but a functioning cluster looks good too. Mike

 

I kind of figured as much. The guy I keep talking to is always hit and miss when it comes to being right. I know this, so I always confirm the stuff he tells me, or tell him he's wrong.

The other day he told me he was dropping an LT1 from a '96 Camaro Z28 into his '78 (I think) Pontiac. He later told me it wasn't an LT1, but a Z34 engine code. I told him he was smoking crack, and that no such engine even exists to my knowledge, only the Z34 car (Lumina or Beretta if I recall). Still, he swore up and down that's what it was. Oh well, pays to test your sources I guess...

At least, I assume he was wrong...

 

you can keep your stock gauge cluster....you just need to get a tach from a v8 car....pull out the old one and slide in the new one...problem solved

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84z28HO
355
open element/k&n
m5/hurst billet plus shifter
83 z28 fiberglass hood
10bolt w/3:42posi
gm aluminum driveshaft
performer intake
performer 600cfm carb
accel 8mm wires
adjustable thermostat switch
160 stat
gta rims
gts blackouts
s.s rear control arms
s.s panhard rod
s.s subframe connectors
98 camaro rear springs,shocks
98 z28 leather seats
95 camaro rear view mirror
"wonderbar"
4th gen z28 tips
14.3@95mph
http://www.geocities.com/toosloz/84camaroz28.html

 

You can reuse it but it may be beyond your capabilities to fix it. I wanted to use my orginal tach because (1) I know it works with my gauge cluster; and (2) it has a 6000 rpm red line which is what I want to see.

I took it out and gave it to a friend who is an electronics wizard. There is a resistor in the back of the tach that calibrates your tach. It is set in for your particular tach at the time of construction. Each one is different. He hooked up a variable waveform generator and kept changing resistors until it was dead on from 200 to 8000 rpm for a V8 engine. Better then any aftermarket tach if you ask me. Calibrated to the last Nth degree.


Anyway, that's how it's done if you want to keep your original tach.

I used my original V6 tach be

 

QwkTrip: Is your friend the Wiz, willing to share with us the modification he did
to your v6 tach to make it read right on a V8.
Ask him which resister (location,value)to change and to what new value (Ohms). Anyone with basic soldering skills can do the rest. Since he has done the re-calibation already to one tach. All the rest of the same design-type can use that same mod too. Will be close enough tolerance for our purposes. I'm sure there must be ton's of us who have done the V6 to V8 swap and would love to correct the factory tach on a budget.
It would make a beauty how-to tech article for this site and you could give him the credit. I checked your bio and I'd be willing to bet we have the same V6 tach.
I checked the wreckers and that dash was
only available on a V6 car, so there is no V8 tach I can swap in there.

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

[This message has been edited by F-BIRD'88 (edited November 03, 2001).]

 

Sorry, there's no way he can remember one resistor value done for a job over a year ago.

 

Do you remember which resistor he replaced?
There is a series of colored stripes on the case of the resistor. the color and position of each stripe tells the value. (resistor color code).

 

Sorry, I'm not going to pull my dash apart to check.

 

Thats a shame... Thanks for all the help....