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| How-To - Interior and Electrical

Modernizing C3 Corvette Gauges

After many years of walking car shows we have seen it all, ranging from incredible builds with amazing attention to detail to the ragged originals, and everything in between. Through the years we have noticed several key areas many enthusiasts ignore and it often reflects poorly on the whole car. One such area is the gauges. We've seen flawlessly painted cars with completely refurbished interiors still using worn and tired (not to mention non-functioning) gauges in the dash. Few things are more important inside a car than the gauges; after all, you will be looking at them every time you drive the car. Fresh gauge faces and accurate readings make a world of difference to the overall driving experience.

As faithful readers know, we are in the midst of bringing a '71 Corvette back to life. The car spent most of its life in sunny Arizona and the interior had plenty of sun damage to prove it. We recently freshened the seats with brand-new leather (from Corvette America) over at Hot Rod Interiors by Glenn. While the seats went a long way to freshening the interior, they looked so good the instrument panels appeared that much worse for wear.

Happily, the solution is as simple as visiting the Classic Instruments website and perusing their offerings. Since they also do custom work, the actual finished product is limited only by your imagination. Choosing custom colors, fonts and pointers is a great way to personalize your Corvette. This is also one of those projects that should be started early in the restoration process since you must allow time for a busy shop like Classic Instruments to complete the renewal of all your gauges. By planning ahead, the gauges will be on the shelf waiting to be installed with the rest of the dash components (Corvette Central) and wiring (American Autowire).

Our Corvette is a nonnumbers-matching car so it is being built as a hot rod. While we didn't want to stray far from the factory look, we were not bound to exactly replicating the factory original gauges. To that end, we decided to go the custom route with the final objective of testing people memories. We wanted people to look inside the car and think at first glance it was all stock, but then to scratch their head wondering, "Hmm, did the '71 Corvette have chrome bezels on the console gauges?" Well of course they didn't, but the look is so period perfect it should leave a lot of folks guessing.

One other major change is the transmission. The car was originally equipped with a TH400 automatic. We decided mixing gears is more fun, so to that end we added a TREMEC five-speed transmission that was custom built by American Powertrain so the shifter will be in the stock location. It all worked out beautifully.

Once we had a good idea of how we wanted the instrument panel to look we placed a call to Classic Instruments to discuss the project. The speedometer and tachometer would be refinished in the factory design but with modified ranges, the tachometer would go to an optimistic 8,000 rpm, while the speedometer would add some visual performance potential by pegging out at 200 mph. Will Editor Brennan be "burying the needle" on these instruments? Not hardly, but we must admit the big numbers add a performance vibe to the interior. Speaking of the speedometer, while we could have used a speed signal from the American Powertrain TREMEC five-speed transmission we opted for the instantly accurate GPS-based (SkyDrive) speedometer. It should be mentioned that the redline on the tach is marked at a realistic 6,500 rpm while the final top speed will be controlled by the final gear ratio, driving conditions, and good old common sense.

The gauge cluster in a '71 Corvette is made primarily of plastics. The combination of 47 years and the high temperatures of the Arizona desert will fade the faces, make the plastic brittle and fog the lenses. After some discussion, Editor Brennan (who also suffers from being brittle, has foggy lenses, and a faded face) decided to go with factory appearance, big gauges. He then decided to add a splash of chrome plating on the bezels of the small gauges. The chrome rings are vintage enough to almost convince people it was a factory option. By using black faces with red pointers, the traditional look continues.

The process on our end was really quite simple. We removed the original gauges and carefully boxed them up and shipped them off to Classic Instruments. Upon arrival, the gauges were carefully examined by the craftsman at Classic Instruments and after a phone conversation we agreed on the estimated price. We discussed the desired work one last time before design work began. Classic Instruments provided us with printed "proofs" of what the actual gauges would look like. We reviewed the design and signed off on the work. After that it was a simple waiting game and soon enough the big brown truck backed up to the door at Hot Rods by Dean with a box full of very fresh gauges.

Of course things weren't quite that simple on the other end. The team at Classic Instruments employ a lot of very high-tech equipment to produce great looking, incredibly accurate gauges. Fitting the modern gauge movements in the stock location is their specialty and when we received the new gauges they fit like a glove; looked better than new (because we really like our subtle design changes) and came complete with senders, instructions, a custom wiring diagram just for our installation, and they even returned our old unused pieces.

We thought it would be interesting to get an inside look at exactly what goes into restoring and/or modifying a set of Corvette gauges. With that thought in mind we followed along as our gauges were dismantled and replaced with new units. You may be surprised to see this very technical process and to see how few parts of the original gauges are actually reused.

Installation in our dashboard proved to be even easier than a factory installation since the Classic Instruments center console panel came prewired. It was a simple matter of wiring to the panel and plugging in the gauges. In no time we had a factory fresh appearing dashboard. In combination with our fresh upholstery the car truly looks brand new. Few things can compare to sliding behind the wheel of a vintage Corvette where everything has been brought back to this high a level. The fresh interior will make driving a pleasure and that new American Powertrain five-speed will keep the needles moving on our new Classic Instrument package. Vette

2. The first step is to remove the gauges from the car. In this case, we sent the entire center gauge cluster along with the two large gauges: the speedometer and tachometer.

3. We also sent the center console gauge panel so Classic Instruments could custom fit the gauges, replace warning lights with LED lights and pre-wire the whole panel.

4. After the gauges arrived at Classic Instruments they inventoried all the parts and began disassembly. Here you can see the speedometer and the gauge itself was in reasonably good condition. The speedometer is showing 41,895 miles. Sadly, the actual mileage just flipped 292,000 miles, which may be a record for C3 Corvettes.

5. After some discussion and a few changes we finally arrived at the perfect look for our gauges. A computer generated image is created and we had to approve that before final work began. This ensures everyone is "on the same page" (pun intended) for the final product.

6. Classic Instruments utilizes the latest technology to construct gauge clusters, like this Buck Rogers' XZ-38 Disintegrator Ray Gun. Well, okay, it is actually a 3-D scanner that plots the location of virtually everything on the panel, but we still think Buck Rogers would love it, too.

7. From the CAD information harvested by the 3D scanner, this backside sheet was cut out by a water jet cutter and attached to the original gauge cluster. It is held in place by the original bolts, and the gauge openings are precisely located.

8. Classic Instruments uses the very latest electrical and electronic gauge movements housed in plastic gauge cups. This provides unmatched accuracy and durability.

9. Headlamps, Door Ajar and seatbelts lights are all housed in the center console on the C3 Corvette. The housing is custom fit to hold LED lamps in place of the original bulbs. First the light housing is marked for cutting.

10. The plastic housing is then cut flush with the back of the gauge cluster. This enables the new rear panel to fit flush. The new LED bulbs will be held in place in the proper hole in the new panel.

11. After being painted in satin black, all the gauges and lights are installed in the panel. Then everything is prewired with color-coded and tagged wires. The plugs permit the console to be removed later by simply unplugging the wires.

12. And here are the new, stylish Classic Instruments gauges. The chrome bezel is so traditional that unless you are a Corvette guru it could easily be mistaken for original.

13. The two large gauges will involve blending the old and the new. The reproduction bezels and new Plexiglas lenses were sourced through Corvette Central while Classic Instruments handled the rest of the gauge work.

14. Forty-seven-year-old plastic is brittle, particularly after baking in the Arizona heat. This small tab broke off during disassembly. Classic Instrument will use a small bolt and special cup washer to replace the broken tab.

15. The original tachometer and speedometer cups are CMM 3D scanned for measurements and then the hole is cut using computer controlled water jet technology.

16. The new tachometer fits inside the original cup with room to spare. The dark red box on top is the parking brake indicator light, and yes, Classic Instruments upgrades that too, with long lasting LED backlighting.

17. The original speedometer cup receives a similar treatment. Here we see the faceplate being test fit prior to having the graphics painted on the plate. The gauge faces are cut using CAD design that operates a water jet cutter for incredibly clean cuts.

18. Here is the speedometer face fully printed. Editor Brennan chose the fonts for the numbers and also opted for a rather optimistic 200-mph gauge. The black face, white numerals and red pointer are similar to the original design.

19. Here we can see the original tachometer/speedometer bezel and the scratched and hazed Plexiglas lens. While Classic Instruments can refinish such items, it was easier to simply order reproduction pieces from Corvette Central.

20. Classic Instruments takes the time to coat the metal cup in a gray finish and the green plastic is as clean as new, it's a class act. Rather than trust the 47-year-old plastic threads, the top cup screw has been replaced with a small bolt.

21. Looking from the backside, the speedometer is completely prewired. Inside the plastic bag you will find pins and plugs so you can wire to the plug. All wires are clearly marked. We opted for Classic Instruments GPS-based (SkyDrive) speedometer.

22. The backside of the tachometer is also prewired. The row of dip switches are set for accuracy. Adjusting the switches is simple and is explained in the directions with the custom wiring diagram Classic Instruments supplies with the refurbished gauges.

23. All we can say is "WOW," they look so cool. Flawless craftsmanship combined with modern movements and accuracy, it just doesn't get any better. This is the tachometer, with built-in parking brake indicator light.

24. Fresh face graphics, crystal clear lens and perfect bezels all add up to one great looking speedometer.

25. We just had to zoom in close so you could see the attention to detail. We really like the clean and simple font for the numbers. The 200-mph marker adds a nice performance vibe to the cockpit.

26. While our engine will never approach the 8,000 point we do like the full sweep design as the pointer position is very intuitive and somewhat proportional to the movement of the speedometer.

Sources

American Powertrain

(931) 646-4836

Classic Instruments

(844) 342-8437

Corvette Central

(800) 345-4122

Photography by Classic Instruments, Taylor Kempkes

wilkinsonfookistand.blogspot.com

Source: https://www.motortrend.com/how-to/modernizing-c3-corvette-gauges/

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