Hi, i have tried to search and keep getting conflicting answers. I am converting from drum brakes to disc brakes and i would like to know weather it will work with the standard 15/16 master cylinder? I know that VL Calais N/A came with 4 disc brakes and came from factory with a 15/16 master cylinder but is there a difference in the calais master cylinder to one that came on a disc/drum car? Vn/Vp came factory with 15/16 master cylinders and they had 4 wheel disc brakes so technically it should be fine. People say that the disc/drum master cylinders had a residual valve which holds 8-10 psi residual pressure to the rear drum brakes, but when trying to look up the part numbers to buy a brand new MC every shop states that its the same part number for vl-vp. so does the the residual valve actually exist in the vl n/a master cylinder? Does anyone have the parts catalog that states the part numbers for the master cylinders? ---------- Post added 05-10-16 at 15:07 ---------- I have answered my own question after spealing to multiple brake shops, for whoever wants to know. The Residual check valve stopped making an appearence after the kingswood/torana's. The VL 15/16 master cylinder does not have a residual check valce for the rear drum circuit therefore waont cause the rear disc brakes to drag. After checking all parts catalogues, all vl n/a , vl calais n/a which came with 4 wheel disc brakes and vn-vr v6 with 4 wheel disc prakes all had the exact same master cylinder. all the models mentioned had the same part number: P10330 So for anyone out there anting to convert to a disc brake rear end the standard 15/16 master should work fine, if you want extra performance then offcourse you would need the 1" master (P10331) along with the dual diaphram brake booster.