So i recently finished my brake upgrade, i converted the rears to maxima brakes,and installed a brand new 280zx MC and 280z brake booster, i do have low vacuum at idle (10 inches) , its a 383 SBC. My brakes go all the way to the floor, and the stopping power really is not that great. Ive bled the brakes with the car running above idle so it exceeded the needed vacuum for power brakes and bles them with the car off. I never changed or removed the proportioning valve.
Any suggestions??