A Re-volting Development
In the June '07 issue of SRM we responded to a letter from Robert Dowdall asking how his car's original 6-volt gauges could be used with a 12-volt system. We suggested some possibilities, including two different 6- to 12-voltage reducers from Ron Francis depending on the needs of the electrical system.
After that column appeared we received some interesting comments. Here are some examples.
Battery Tap
You omitted the easiest solution to dropping voltage. Back in 1955 I installed a 265-cubic inch Chevy in my '41 Ford with the Chevy 12-volt starter and generator, and the first time I fired it up the stock '41 gauges fried.
For a fix I tapped a bolt into the 12-volt battery at the third cell, which gave me 6 volts. I ran a wire to an off-and-on under-dash pull switch. With the switch off I'd start the car in 12-volt mode. Once the motor was running, I'd flip the switch on and all the gauges worked fine on 6 volts.
I kept the car two years, then sold to a friend who hounded me. I kept the stock driveline, but it was weak so I would have to ease off the line, but once rolling it would wind and wind. I felt like it could twist to 7,000 rpm but I never knew for sure. It was tons of funWm. Van SciverSomers Point, NJ
While we've seen batteries drilled and tapped before, it's not something we would suggest, particularly with modern batteries. But we have to confess we found a way to do something similar a long time ago with a VW 12-volt battery that had a built-in 6-volt terminal. But we stick with the options we suggested in the earlier column.
Another Re-volting DevelopmentI read your shop manual answer about 6-volt gauges being operated in a 12-volt system in the June issue of SRM. I messed around with voltage reducers for years trying to find one that actually put out a consistent 6-volts, but here's a little trick that maybe you know already.
I have a '41 Ford with a small-block Ford and original gauges that I wanted to keep. I went to a junkyard and bought water temp, oil pressure, and voltage gauges with the matching senders, figuring there had to be a way to adapt them into the original cases. The gauges were from a late-'70s to early-'80s Ford pickup. I disassembled the '41 gauges, disassembled the new gauges, and the new Ford movements fit back into the original cases like they were made to be there. In fact, the two sets were so identical I had to mark them so I wouldn't mix them up.
As the new gauge cases were plastic, the needles stuck out a bit. So when they were installed in the '41 housing, the needles contacted the gauge cluster glass. Rather than trying to bend the needles, I glued No. 8 flat washers to the gauge cases at the mounting holes. That spaced them away from the glass correctly. I replaced them in my car, hooked up the late model senders, and they register exact. Now it appears I have original gauges, and it cost me $3. I used a Ron Francis VR-1 to operate the '41 fuel gauge and old style sender. After installing the speedometer it kept breaking cables a couple times a year. I found out the speedometer drive head was seizing. There is a small lubrication hole with a "wick" where the cable attaches. I added silicone oil as I turned the speedometer with an electric drill. I added all I could get in and haven't had a broken cable in couple years. Also, I've had no good luck with "cut-to-length" cables. The end that I crimped on always seemed to be a bit off and caused the speedometer needle to pulsate. I finally used 2-ton epoxy to bond the cut cable to the end; it stayed straight, no pulses in the needle. Another note: Did you know that all Ford gauges and speedometers are adjustable? Two holes in back of the gauges will adjust the swing of the needle, left and right. The speedometer is adjustable via a lever on the inside, near the needle. Clockwise increases the reading, counter-clockwise decreases it. My '41's speedometer matched the original 3.78:1 rear gears. Now I have a 9-inch with a 2.73:1 rear, and I adjusted it as above and it reads within 1-2 mph of my buddies hi-tech speedometer and with the "your speed radar signs." Sure beats trying to find a drive gear to make the speedometer read correctly. This may work with other makes as well.Don PatersonElmira, N.Y.