If you plumbed the new manual proportioning valve the same as the stock one, it will limit the pressure to the front brakes while running the rears at full pressure. This worked because the rear calipers are tiny and are pretty much incapable of locking even the stock 205-70x 15 rear tires, causing a skid. I suggest that any proportioning valve is unnecessary on street Panteras, but if it is desired, it should limit pedal pressures to the rears rather than the fronts, just like most or all other cars. I put one in this way and found that it made little difference over the whole possible range.
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