Have you tried buying a '68-'70 instrument cluster with the 140-mph speedometer and 8,000-rpm tach recently? More than likely, your wallet hurts just thinking about it.
Today's treasured 140/8,000 clusters were rare to begin with. In 1968, barely 2 percent of Mustangs were equipped with the optional tachometer cluster, the majority of them with the standard 0-120-mph speedometer and 0-6,000-rpm tachometer. Only Shelbys got the coveted 140/8,000 versions that year. So you can thank demand and rarity for today's high prices.
Gentry Zentmeyer at Auto Instruments points out that you don't have to have an original 140-mph speedo or 8,000-rpm tach to install one in your '68-'70 Mustang. Auto Instruments can convert 120/6,000 to 140/8,000 units. At the same time, the company restores the gauges, a process that includes repairing, calibrating, stripping, and refinishing the gauge faces; repainting the pointers; and restoring the cluster housing with new plastic-chrome, paint, and exterior finish. If you don't have the tach cluster, Auto Instruments can convert your 120 speedo to 140 status.
Auto Instruments offers instrument repair and restoration for all vintage Mustang instrumentation, including conversion to quartz movement for clocks.
This is an original '68 Mustang...
This is an original '68 Mustang instrument cluster with the optional tachometer. Like most, it's fitted with a 0-120-mph speedometer and 0-6,000-rpm tach. We're following along as Auto Instruments converts it to a 140-mph/8,000-rpm version, as found in Shelbys. Auto Instruments can also make the conversion on '69-'70 gauges.
With the speedometer disassembled,...
With the speedometer disassembled, you can see the rust on the speedo drive (right), which fits inside the aluminum housing (left). Auto Instruments' Gentry Zentmeyer says the grease has deteriorated to the point that the metal driveshaft is rotating against the soft aluminum, causing excessive wear in most vintage speedometers. That's why you experience a bouncing or noisy speedometer needle.
Auto Instruments restores...
Auto Instruments restores the speedometer housing and fits a new drive and magnet. While drive assemblies are no longer available new, Auto Instruments still has a large supply. Interestingly, the magnets aren't magnetized when installed. Auto Instruments uses a speedometer calibration machine to add or subtract magnetism to calibrate the speedometer to the numbers on the face.
Part of the Auto Instruments...
Part of the Auto Instruments conversion is the restoration of the gauge face. Using the original face, the company bead-blasts the metal to remove the original paint, then repaints it black before rescreening the numbers, from 0-140 for the speedometer and 0-8,000 for the tach, with ink like what's from the factory. Decals aren't used.
Odometers are also restored....
Odometers are also restored. Here you can see the comparison of an original odometer with dingy, yellowed lettering and an odometer that has been relettered by Auto Instruments.
The recalibrated drive unit...
The recalibrated drive unit and relettered face are put back together as a 140-mph unit. Auto Instruments lubricates the assembly with modern grease, which is much improved and longer lasting than the grease used in the '60s.
Once the speedometer is reassembled,...
Once the speedometer is reassembled, Auto Instruments double-checks the calibration for 0-140-mph operation.
Unlike speedometers, tachometers...
Unlike speedometers, tachometers don't have a drive unit to wear out. After restoring and relettering the face to 0-8,000, the tachometer is electronically recalibrated. In many cases, the original circuit board has gone bad, so Auto Instruments replaces it with a new one. Gentry says that many original tachs are off by as much as 1,000 rpm, which can be a big deal if you think you're shifting at 6,000 rpm but it's actually 7,000 rpm.
During a complete cluster...
During a complete cluster restoration, Auto Instruments also restores the smaller fuel and temperature gauges. Gentry says most are still in good operating condition when they come in. Pointers are stripped of their original paint, then coated in white before applying fresh translucent orange to match the factory hue. He adds that the pointers must be stripped to bare metal before repainting. Painting over the old paint adds weight that will throw off the gauge calibration.
Quartz movement is typically...
Quartz movement is typically added to clocks. Auto Instruments can rebuild a clock per original specs. However, Gentry says that dependable operation will only last a year or so. With modern quartz operation, expect 10 to 15 years of operation.
The gauge housing is also...
The gauge housing is also restored by Auto Instruments before reassembly of the cluster.
Auto Instruments replaces...
Auto Instruments replaces original voltage limiters with a solid-state unit. The limiter converts the car's 12-volt power to 6-volt for the gauges. Original limiters can fail, sending a full and fatal 12 volts to the gauges.
Instrument bezels are also...
Instrument bezels are also refinished, in this case with woodgrain. Auto Instruments' plastic-chrome vacuum metalizing process is identical to Ford's process when the cars were new.