Just picked up a 1978 Starfire Firenza today. It is a 4-speed with the Chevy 305 (factory, I know, I know, the plan is to unfactory it with an Olds powerplant). It runs real good, but in 4th gear at 40 mph the tach reads 4000. Seems a little high to me. At idle it reads 1100 and it certainly does not sound like it is at 1100. I plan on picking up a cheap tach to hook up and check but I have some questions.

1. Can I have two tachs hooked up at the same time?

2. Any advance thoughts on why the tach is reading high?

Here's the first pictures:

 

Wait, forget question 1. I know I can have two tachs hooked up. Would like any insight on question 2 though.

 

Yes you can hookup 2 tachs, your factory tach might need recalibration.

 

Well it's way cooler looking than the 442's of the same era. I guess if I hadn't liked monzas in high school I might not have the same opinion. Maybe it's a tach for a 6 cyl? Yes, you can run two tachs at the same time. If there is an ignition amplifier (msd, hyfire, etc...) you need to address those issues.

 

Came from the factory with this tach and electronic ignition (and rear sway bar, schwing!). I'll have to look into recalibrating it.

 

There's a thread over at Oldspower that suggests that the '80's Olds tachs had a tendency to have their plugs get loose or fall out. Either condition causes the tach to act like a 6 cyl or 4 cyl tach. That sounds like what mine is doing. I'll take a good look at it this weekend.

 

There's a switch or a jumper on 80s Olds tachs that will go from 8 to 6 and read high.

 

Schwing is right! Cool car man. Got factory stuff and it shouldn't be too hard to fix: