Lonnie P

I am trying to find info on the V6 tach in a Firebird.

I have a V8 Formula, but the factory 6K tach will be useless with my engine.

I also have a V6 cluster with a 8K tach. Will this work without a converter box, using only the LS1 PCM tuning to correct it?

Also, I found out that the V6 & V8 use the same oil pressure sender, but the V6 has an 80 psi gauge & the V8 a 60psi one.
What oil pressure is everyone typically seeing with their LSx engines.
I have both gauges & have to make a decision.

Also does anyone have a spare 140mph speedometer they want to get rid of for a reasonable price?

Thanks for any info you can provide.

Z28ricer

iTrader: (2)

Yes you can reprogram the pcm for the correct tach output.

Lonnie P

Thanks,
I saw a bunch of info on swaps into V8 cars, but little mention of the V6 tach.

Any idea of the tach settings to start with?

25th327RS

iTrader: (2)

I am not familiar with firebird clusters, but the 90-92 Camaro clusters have a small board in the back of the cluster that runs the tach. That's where the difference is, not the guage its self, which allows you to swap v6 and v8 tachs in a cluster and read the same(just with the higher v6 redline). Wondering if the firebirds are the same way, might be an easier route if it is.

QwkTrip

iTrader: (22)

I have an '89 Firebird with V6 tach. I'll tell you what I did but it won't be possible for the majority of people. I happened to have a friend that owned a waveform generator and I loaned him my tachometer. He figured out which resistor is used to calibrate the tach and swapped it for different resistor. He jokes that I now have the most accurate factory tach on the planet.

Keep in mind I did this for a small block Chevy swap so I didn't have LS1 computer controls at the time. Fixing through programming of software was not an option.

Z28ricer

iTrader: (2)

The LS1 tach output is 4 cylinder to start with, you have to program it either way, so both of those options add an extra step, and still require programming.

QwkTrip

iTrader: (22)

Yep. The only value to what I did is improved accuracy, especially near shift points.

Lonnie P

Now I have more choices....
Today I bought (off a member here) a 140mph speedometer & 8K V8 tach w/ 6k redline so I can use them.

I used the 80psi oil gauge since I had it.

Guess I'll sell off the 2 V6 clusters I have.

Thanks again for the info.

25th327RS

iTrader: (2)

Which v8 would have had a 8k redline? I was always under the impression 305s redlined at 5, 350tpi cars had a 5500 redline and the 6 cylinder cars were the only ones to have a factory 6k redline tach...?

Lonnie P

You are correct... I mistyped the info.

Both are 8K tachs , but the V8 has a 5500 & the V6 has a 6K redline.

To answer your previous question, the Firebird tach has an integral citcuit board.
I was looking at it yesterday & there appears to be only 1 resistor different between the V6 & V8 board.
Not sure if the chip in the board is programmed differently though.