67 goat

When looking for info, I searched and didn't find anything, so I figured I'd post my experience now that my issue is fixed.

We had to set the tach ouput setting to 3 to get the tach to read correctly. Now it's perfect!

Probably not alot of guys running factory hood tachometers with LS swaps, hence the lack of info.

Hope this helps someone else.

Thanks,
Jeff

oldgoat69

I also have a factory hood tach. I missed your full instruction on making the tach functional. What does it take?

67 goat

Just wire the tach output wire (from the PCM) to the tach input wire on the tach......where it originally came from the coil (or electonic ignition module). Leave the 12V and ground wire as-is.

Thanks,
Jeff

oldgoat69

I will give it a try, thanks for the hint.

lizeec

iTrader: (57)

Which PCM are you using? I also have the factory hood tach on my 66 GTO I am using the E40 PCM from a 2006 GTO and harness from the 2006 also my engine is a LS2 & T56 from the 2006 GTO, but to get it to work I had to use the SGI-8 box from Dakota Digital.

andrew69_04

iTrader: (148)

if i remember correctly, 3 is the correct setting for a v8 tach. V6 runs on 4 and i believe 4cyl cars run on 6 (which is what the ls1 uses from the factory)

rsimons

Did it require a pull up resistor? If not, do you remember what it did before you changed the ecu setting? I just hooked mine up as you described, but have not reflashed the ecu yet. Light comes on, but the needle doesn't move. I expected it to move but be off. I fear the tach could be bad.