December 1, 2004

En-Gauging QuestionI have a '73 Mustang convertible with a 351 Cleveland. The car did not come with the full instrumentation (tach, oil, amp, and water temp gauges). I would like to install the full instrumentation and have already obtained the factory instruments, but not the factory wiring. I've seen several '71-'73 Mustangs featured in your magazine, and it was stated in the description that this change had been performed. Can you advise me on how to proceed or who I can contact to perform this installation? If you believe aftermarket gauges would be a better alternative, please advise the best choice.Glenn HepnerVia the Internet

Unfortunately, factory instruments for '71-'73 Mustangs require the use of the factory wiring harnesses. The oil-pressure and water-temperature gauges can be hard-wired in as long as a gauge voltage regulator is included on the power supply side and the correct sending units are installed on the engine. However, the ammeters are not so easy. Mustang ammeters do not carry full amperage through them like aftermarket or test equipment gauges. Instead, they take a sample through a shunt, which is part of the factory wiring harness and is not possible to duplicate easily. These shunt-style ammeters are not known for their sensitivity and are a source of complaints from many Ford owners. The ammeter requires the factory harness.

The tachometer can be installed easily as it simply plugs in between the ignition switch and resistor wire lead to the coil. Locate and cut the red/light green wire on the ignition switch and connect the two ends of the cut wire to the leads from the tachometer, with the red tach lead connected to the switch end and the black tach lead connected to the harness end.

Although factory gauges are desirable, the installation is different compared to a set of aftermarket gauges that are designed for an easy installation. A large variety of aftermarket gauges are available, so shop for the set you like and can afford.

Slick QuestionI own a Dark Ivy Metallic Green '69 Mustang convertible with an inline 200ci six-cylinder. It's backed by a three-speed manual transmission and a 3.20 rearend. The engine turns 2,800 rpm at 65 mph and 3,000 rpm at 70 mph. Awhile back, a friend suggested I use 5W-20 motor oil, but it looked a little thin to me. What grade of motor oil do you recommend for a 34-year-old engine: 5W-20, 10W-40, or 20W-50?David D. FloresVia E-mail

With all the engine oils on the market these days, it's easy to become concerned about the best to use in our older vehicles. Motor oils must evolve with changing engine developments. Because of requirements for cleaner burning and better fuel economy necessary for modern engines to meet ever increasing standards, many types of oils are now produced. Basically, oil quality has improved along with each new requirement; however, the amounts of some of the older anti-wear additives such as zinc and phosphorous have been scaled down. A few oil companies are beginning to market oils for older, high-mileage engines as these vehicles are not required to meet the standards of their newer counterparts.

I like the new Valvoline 10W-30 oil for engines over 75,000 miles because it has an additive package designed for older engines. The 10W-30 viscosity has been recommended since our Mustangs were new and still is an excellent all-around choice. Oil choice is certainly a matter of opinion, but two things will always remain true: Frequent oil-change intervals must be maintained regardless of oil choice, and synthetic lubricants last longer and protect better than organic-based products. I use Mobil 1 synthetic in my vintage race engine to protect those expensive race parts. I use an occasional quart of the Valvoline High Mileage in my oil-leaking '65 coupe (between oil changes, of course).