Project Cortez

iTrader: (3)

I'm putting in a LS1 into my 69 Camaro and want to keep the interior stock. There is a kit for the LS1 to work with the stock 1969 Speedo but does anyone if there is a kit or some way I can keep the stock tach??? Thanks

fast400

iTrader: (1)

Dakota digital makes a box which will convert the signal for your original tach.

Chris442

iTrader: (1)

You can reprogram the computer to make the tach work right off the wire from the computer. That's how the tach works in my '68 Camaro.

shanekennedy

iTrader: (1)

i don't own a dakota digital unit, but from what i've read, their unit causes the speedo to jump around a lot during quick acceleration. i was considering swapping the guts of my original speedo w/ the guts of a cheepo digital unit off ebay. should be able to program pcm to calibrate guts w/ numbers on faceplate.

thunderstruck507

iTrader: (18)

there is a company that makes a tailhousing with both VSS and mechanical gauge output, but it's like $500

the tach will work stock, just reset the computer

Project Cortez

iTrader: (3)

Thanks for all the great info. Glad to hear I can keep my stock speedo and tach.

ls1nova71

iTrader: (4)

What exactly do you reprogram in the PCM? And will it work on a 98 PCM? I haven't seen my factory tach move in 8 years, would be nice to have it work again.

thunderstruck507

iTrader: (18)

its a single wire in the harness, connect it to the factory tach wire, then switch from 8cl to 6cl mode (iirc)

mine work perfect

ls1_catera

anybody happen to know the pulse count for the F_body tachometers??? the ECM tach output should be a pulse count for the stepper motor tachometer in the instrument cluster. in older units, the tach pulse factor was stored in the EEPROM.

Chris442

iTrader: (1)

In HPTuners, under the engine - general tab there will be Tach output with "Resolution - High" and "Resolution - Low listed." Both of these should be 6 in the stock program, and IIRC they both need to be changed to 3.

The tach signal comes from the crank sensor, and LS1 tachs run in 4 cyl mode, typically. The earlier motors have 24 tooth reluctor wheels and 24/6=4, so you need to change it to 3 to get 24/3=8.

My LS7 has a 58 tooth wheel, so there's no simple solution since these numbers have to be integers, but making one number 8 and the other 7 made the tach right on the money for me.

Rodder

iTrader: (2)

For the speedo, get a CableX box. For the tach, just scale the PCM output with HPTuners. Both have been done many times by people on here!