Doing so many things to this truck that I'm all over the place. The "Green Diamond" engine is a 233CI straight flathead 6-Cyl. It is rated a whopping 93 HP at 3,400 RPM, 181 ft. lbs. of torque at 1,000 RPM's, and has a compression ratio of 6.3:1.
So how are you supposed to know what the RPM's are of the engine when you don't have a tach? So I created a tach based on a photo of one that I got off the web. Although the engine has a redline of 3,400 RPM, I went with a redline of 3,000 RPM which I felt was far more comfortable on the old engine and a means to protect it. Photo #1
I started with a 3" diameter body VDO tachometer, 12-volts to match the 12-volt conversion I did, and pulled the tach apart. I then removed the plastic tach facing which I wanted to have changed to resemble the look of an original 1948 style tach. Photo #2
I searched the web and found a company in Florida, CAD Graphics Home - custom dials, gauge dials, pressure gauge dials, CAD Graphics Inc
, that offered custom designed gauge face overlays. I sent the plastic VDO face plate along with my design I drew up and the fine points I wanted incorporated into the design to be used in producing a custom dial overlay (old style font, triangle type RPM indicators, & the International logo). Emails were exchanged until the final design was approved by me. Near complete, the face has a white background, but the older gauges had a light tan background. So this was corrected and the final design accepted. Photo #3
is with white background.
The overlay was then applied by CAD Graphics right on top of the VDO faceplate and matched the RPM sweep exactly. It was then mailed back to me. The price? $50.00 plus shipping! Great value.
I reassembled the tach for a test fit. I made a wiring harness for the backlit lights and swapped the 2 filament bulbs for 2 tower LED bulbs - less amps used. The bulbs were so bright that the VDO tach, which was designed to allow the back lighting to show through the RPM numbers and scale lines did just that, and bled right through the custom dial face. To correct this, I simply used black model paint and a brush and covered the RPM numbers by painting over them. I left the RPM scale lines which are on the outer perimeter of the VDO tach face to bleed through which matched the RPM scale lines on my custom dial face. So this now back lit the perimeter of antique face so you could see the RPM scale lines at night when the lights were turned on. An added bonus I did not even consider.
The RPM needle/pointer from the VDO tach had a bulky contemporary design and I wanted to use a RPM needle/pointer that looked correct for the era. I used the pointer from another tach I had and had to modify the VDO needle. I then used JB Weld to overlay the older style needle on top of it. I gave it a coating of Chevy engine orange.
With the bezel still off, and the RPM needle still loose, I tested it on the KB5 engine. I hooked up the power to activate the tach and then disconnected. This is said to position the tach electronics where it should be with the RPM needle set at "0" RPM on the scale. I then pressed the needle onto its shaft, but just enough to keep it engaged, and so I could pull it back off if the needle was incorrect in its position.
I fired up the engine and the tach came to life. I measured the RPM's against my 1980 Craftsman engine analyzer with its RPM scale - it was a match, the tach RPM was the same as my Craftsman tach.
I then pushed the RPM needle down on its shaft for the final time and reassembled the glass/bezel. Photo #4
I used a section of reproduction cloth covered 18 Ga. green wire from Rhode Island Wire to match the rest of the wiring under the hood. Located a place on the dash where I wanted the tach, and used a 3 1/8" hole saw to make my hole. Cut, soldered ends, and used heat shrink wrap on all wires and plugged them into the back of the tach. I went with a separate toggle light switch connected to my fuse block & a 3 AMP fuse. Inserted the tach in its place and secured it all together. Looks and operates like factory, and no guessing how many RPM's the old engine is turning. Photo #5
, 6 & 7.