Larry; the problem is your're only getting 6/8ths of the correct
reading. The stag tach is calibrated for 8 cyl..Your only feeding it 6/8
of the revs per min that it was set for.
Don't panic! If it's an electronic tach(not cable driven), here's what
to do. There should be a potentiometer inside the tach that should allow
for a wide range of adjustment. I converted a Smiths Alpine tach for use
in a Tiger using this method. You need to remove and open the tach, and
find the "pot". Drill a hole in the metal case so a screwddriver can be
used to turn the pot from under the dash, after it's reinstalled. Or, if
you can, find some way to prop the tach up with the case removed for
access.
Then, put a second tach on line that is known to be correctly set for 6
cyl., a good tune up type tach will do. Then calibrate the Stag tach to
the other tach. Turn the pot screw to match the 2nd tach as closely as
possible. Use several rpm ranges for comparison, say 1500, 3000, 4500.
Hope this helps!
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