Where to start?
I have a m21 4spd, 3.55:1 posi, 275 60R15 tires on
A 67 big block 4k car.
I calculated the required speedo
Gear to be 17 teeth - purple gear.
When I put it in and drove the car over 60,
My speedometer spun out of control. It spun to
120 mph and made a god aweful high...