Sorry if this in is the wrong place as I saw no clear cut forum for it.

I just finished a LS1 swap and now my tach is off. About 70 RPM at idle and it grows to about 350 RPM at 5k (The PCM pulses are set right to drive a LT1 tach). I was courious if anyone knew if there was a dashpot on the tach circut board for fine tunning the adjustment. If not, is there anything else I can do to fix it?

Re'

 

i know my gauge is off by 250 it always says 1000 but its at 850 on the scanner

 

There are tach output parameters that can be changed in the PCM. Perhaps tuning these values could make the tachometer more accurate?

 

All that changes is the pulses per revolution the PCM puts out. I only need to trim it by about 5%. My error is also not constant. It grows with more RPM. I'll have to find a gauge cluster in a salvage yard I can tear apart. I'll bet money there is a dashpot for finetunning it on the circut board.

Re'

 

I think all these cars have tachs that dont read right.