Some months ago, a note appeared in the Tiger Tracks about a conversion by a speedometer shop of the stock Tiger Tach to 7,000 RPM indication at a cost of $32.50. For Tiger owners willing to invest a little time and effort (sort of goes with owning one), there is a much less expensive way to get a nice, accurate, matching 7 grand tach.
Except for the faces, the 1725 Alpine (series V) and Tiger tachs are identical - there is no difference. Hard to believe? Its true. The Tach has an adjustable pot inside whose range of adjustment is sufficient to allow accurate calibration for 4, 6, or 8 cylinder operation.
Simply scrounge around for an Alpine tach (must come from a Series V or 1725, 66 or later and say negative earth on the face.) These can be bought for $10-15 in wrecking yards (George Fallehy ?) Its a good idea, after taking the meter out of the case (2 screws on back), to really douse the guts with an evaporative type electronics solvent (e.g. Spray - Kleen) to clean out the dust, goo and cobwebs. Then hook up the tach hanging under the dash - you may have to splice in a couple of feet of wire into the ignition circuit. (white pick-up wire) and use some extension wires with alligator clips for power and ground. Then using your trusty dwell-tach or engine analyzer, youre ready to calibrate it.
The little black and white pot on the back is used to adjust the indication. The whole outside rim turns - turn it s l o w l y. You may have to loosen the center hold down screw a tad. Crank up the engine. Holding the speed at 1500 RPM (by the control tach), set the pot - fairly close. Now advance the engine speed to the RPM you desire to be exact, and fine tune it. Actually, mine, set right on at 3,000 is within 50 RPM at 750 and within 100 at 5,000 (the aforementioned cleaning helps,) so I would recommend using ones head about calibration - holding the durn thing at 6,500 long enough to set the pot and tighten the hold down might not be all that wise. When you think you have it, carefully tighten the hold down a bit, then cycle it up and down the scale a few times to check it. If youre still satisfied, tweak the screw to hold it, and youre done. To make a perfect conversion, get some satin gloss black model railroad paint and a selection of rub-on or decal numbers from your nearest hobby store that deals in HO gauge trains. Paint out the 4 and stick on the 8. Slick!
Some other things that are nice to know about your tach. If it (stock or converted) wont work sometimes but will at others, check the big .025 mf capacitor near the transistors: its probably cracked or leaking. Get a replacement at Radio Shack and solder it in.
If it is sluggish in cold weather and does strange things sometimes when it gets real hot (Holtville ?) you can thank the inferior transistors used in Smiths instruments. Back to Radio Shack. Buy two general purpose Silicon transistors. If you want to be perfectly correct, tell the salesman you want 2 Motorola HEP 253 transistors or equivalent. Just clip out the old ones and solder in the new. If youre a little afraid, go and see your T.V. repairman - tell him what you want and it will take about 10 minutes (both transistors, capacitor, and a cup of coffee). Actually, replacing these troublesome parts when making the Alpine-Tiger switch is a real good idea (only about $3-4 worth of parts). If you dont, you may have to recalibrate the instrument if you ever do.
If you install a C-D ignition (a good deal) you have to do two things: 1) take out the second set of points in your dual point distributor (if you have one); 2) rewire the tach as shown. Note - just take out the nylon bracket and use only the metal loop - 4 turns works really well and fits nicely. Recheck your calibration!
T. Ballou
4/7/75
