I bought an 86 firebird with a 350 engine but was originaly a V6 car. I need a way to calibrate my tach so it will read even close to what it should. I have read they can do it with the s-truck engine swap but I can't find facts. The car has a really nice guage package so I would like to keep it. Thanks.

 

You need a V8 tach.

 

My brother has recalibrated tachs to work with V8s that never had them- even a weirdo rotatry engine tach in an RX-7 that got a V8 transplant. It's basically at it's heart a change of a single resistor inside the tach. Knowing which one and how much to change it, though, is the real trick. I guess being an electrical engineer like he is helps.

 

If you look at some of the Toyota truck 4x4 sites they swap in 4.3's and 350's in em and what they do is wire a pot onto the motor of the tach. Then you adjust it to read correctly by hooking up a multimeter to the engine or using another tach. Do a search for it on google and you should find it. I've did it to my cluster but I havn't gotten a chance to try it(no engine in car ) If I remember right the pot was either a 10k or 5k ohm linear taper. I got it from radio shack.

 

all the rotary tach should be is a standard 4 cyl tach

thats it