I'm working with a 1989 Firebird Formula 350 TPI that has been engine swapped and switched to carbureted, and I wanted to keep all the stock gauges on the dashboard because I prefer the aesthetic of them. Would I be sacrificing precision of their readings if I kept them instead of swapping them all out for AutoMeter gauges? I've read on the water temperature being inaccurate sometimes, and ive got the MSD tach adapter on its way to the house, but I wanted to hear from you all if the stock gauges are really as imprecise as some users here seem to suggest.

 

Here is how stock gauges should be treated in any car.

The needle normally runs here on the gauge. Now it isn't running there. I might want to look into this.

 

If you haven't noticed; the Temp gauges on modern cars don't have numbers. They basically indicate Cold, Normal, and Hot. This way people aren't concerned with numbers, but rather if the needle is in the "Normal" range...

 

So I totally agree w the prior statements. When I did my initial engine swap years ago I put in a zz4 w a pro Flo efi. The pro Flo ecm pulled temp from the intake and the stock gauge pulled from the head. They were about 15-20 deg different and I know part of that is from the location. The stock oil pressure gauge was always pinned at startup. Once warmed up it actually was in a similar ball park as my auto meter. But it wasn't as responsive. If you blipped the throttle it showed on the auto meter but not on the stock unit. Also the tack was pretty accurate when compared to the ecm readings. I'm aware the stock gauges are far from ideal. Mine were OK, but I've seen some that were really bad.

I think stock gauges give you an idea that things are kind of ok or not. But thats assuming they're working well. I pulled my stock dash at replaced w autometers years ago.

 

My factory tach was and is almost spot on. Voltage is close. Temp gauge is the least accurate.

 

As the old maintenance adage goes ("If you want to know what's wrong, you should first know what's right").
Gauges are a huge improvement over tell tale lights, and if you watch the gages when things are working well, you can tell when things go wrong.
Don't get to fixated on the numbers. Generally when things are good, the gauges do run near the middle of their sweep.

 

My tach is off a hair according to my innova timing light with rpm function. When the gauge reads just under the 1000rpm line (maybe975rpm?) I am actually somewhere around 900rpm. This is obviously nit picking something never intended to be that crazy precise.

The coolant temp gauge in these cars get a lot of flack for inaccuracy and I'm sure some are but mine is pretty on the money all things considered. The gauge lines up pretty accurately to what an IR thermometer reads as well as the set point for my fan controller.

as others have said, the gauges are just for reference. you know you're good when you're "somewhere around" 180 degrees Fahrenheit". the cause for concern would be when you're "somewhere around" 240 degrees F"

 

If my voltage gauge is giving a reading I don't like (usually low), I just give the cluster a smack and it smartens up. '89 IROC.

 

I'm glad this thread came along. I was paying a little more attention to the gages than I normally do and noticed the voltage gage reading low coming home from a car show.


When I got home I did some voltage readings.
11.96 vdc. with engine running and parking light on.
12.0 vdc. Engine stopped and lights off.
I ordered and replaced the alternator with a ACDelco remanufactured unit. The remanufactured unit has the back mounting hole threads stripped, so the remanufactured alternator is now mounted with two bolts for now..
The remanufactured alternator is charging well and the voltage looks good.
Running well.


I also ordered a rebuild kit from Tuff Stuff and installed the parts in the old alternator thinking I would just reinstall the original alternator back in after it was rebuilt.
I cleaned up the slip rings.


I then installed the rebuild kit parts.


After the rebuild I installed the original alternator and it did not charge. I even jumped the 1 and 2 terminals to the battery thinking that I might need to excite the field windings for the first initialization run, but no joy.
I noticed a couple of items in the rebuild kit that I couldn't see on the parts layout diagram and so I didn't install them. Does anyone know what these two parts are called, and where they should be installed?




Plastic block or spacer.
When the weather cools down and I am not out touring I'll have another go at the rebuild. For now it's working well.
Yes I did install the stator windings and removed the wire that keeps the brushes in the brush holder, after the rotor was installed.
If anyone has any thoughts about what I may have done wrong, please let me know.

 

The "block" and the clip look like they're for making it a 1-wire alt. The "block" would then have a jumper inside it, and would plug onto the connector from the outside. The clip would go across one of the regulator mounting screw pads.

 

The issue did indeed turn out to be the clip as it needs to be installed on the brush holder to provide the ground path for the voltage regulator. Thanks Sofakingdom.

The clip needs to be installed here.







The black plastic block as stated is just a dust cover if the alternator is a one wire configuration.
The original alternator is now back in and working properly, and it has the same patina as the rest of the engine so I'm happy.

 

Yeah Sofa knows a thing or two...