I have a 91' camaro RS wit a carb 305, also running off a msd 6T, I just installed a tach in the car but it wont read right, the car will be idle at 1000 rpms but the tach will read about 6000 rpms, I know its not the tach tho cuz this is the second one, the first one did the same thing so I trashed it, only to find out it was probably fine. its wired up the right way I just dont know why it would read off like that........ anyone got any ideas????

 

By the right way, you mean that the tach is connected to the tach terminal on the box?

 

what brand of tach is it and did u ckeck the wires on the back ? u may have wired it up for 4 or 6. that may be our problem.

 

its a mac tools racing that is only for 8 its not adjustable....... :/

 

the tach is wired to one of the wires going from the msd to the coil, the orange one to be exact. im not to sure i know what you mean about the tach terminal, this is the first time i have ever messed with wiring

 

That's not the right way, you can't put the tach on the coil primary with an MSD box. At low RPM it's firing 5 times per cylinder, so your tach will read 5 times higher than the engine is really running. The box has a a separate terminal just for driving the tach, check your installation manual.

 

i agree with apeiron he has a good piont

 

Thanks guys, working great now, I thought I had it right cuz I was using the tach installation manuall for a stock car with out the msd. I really appreciate your guys help.