S197 3V Converting 2007 Mustang GT to Manual brakes for road racing? Thoughts?

[GRUF78]

Pro built Spec Iron 2007 Mustang GT road race car. Drove the car for 2+ years in a multitude of track events with zero issues. Now constant brake problems -hard pedal. 2 master cylinders, 2 new boosters , lines, bleeds, rear calipers et al...even replaced the booster check valve with a steel one from Earls' with no fix. Car has 4 piston Brembos up front and OE sliders in rear.

Before I go medieval and go complete manual/prop valve on this car-What am I missing?

Thank you,

GRUFF

 

[blacksheep-1]

What are you using for calipers?

 

[GRUF78]

gt500 4 piston brembos up front. OE sliders rear.

 

[Reloader]

I'm not a brake expert by any means. But I do have experience with manual brakes on a track dedicated car.

When I converted my non ABS 944 turbo to LS1 power the brake booster had to be removed to make room for the motor. I had adapters fabricated so that I could run GT3 6 piston calipers in the front and retained the 4 piston calipers in the rear. I installed a wilwood proportioning valve on the dash which was dialed in and marked so it could be returned to the proper position after brakes were bled.

I ran Hoosier or Kuhmo scrubs.

The car was tracked in this configuration from 07 until I sold it in 14.

Once the proportioning valve was dialed in it took me very little time to get used to the brakes without the booster. I even went to a BMW master cylinder that was 1mm larger in diameter and there was no noticeable increase in force required.

YMMV