I recently installed rear disc brakes to go with front disc brakes I put on a couple years ago. I installed a proportioning valve for the front disc/rear drums. The car stops, but the pedal is extremely low for four wheel discs. I don't think I have air in the line. Could be a vacuum issue and the power booster isn't operating properly or it could be that I need a front disc/rear disc proportioning valve. Has anyone ever had this issue?
I had a 1970 with front disc, hold off valve and distribution block that I converted to four wheel discs by changing the master cylinder, removing the hold off valve and running it like that. When I do a panic stop it just every so slightly will skid the rear tires. I want to put an adjustable prop valve in it eventually but I haven't felt I needed it yet. It stops so much better than when it was a front disc/rear drum car and would lock the rear tires way to quickly. Did you change the master cylinder? My guess is your master cylinder doesn't have enough volume for the rear discs.
Greg - Thanks for the reply. I did change the master cylinder to accommodate for the additional volume. I have everything plumbed underneath the car to the where the original proportioning valve was located (don't like the look of the conversion kit, where it has the bracket underneath the master cylinder), so I think I'll purchase the disc/disc valve and replace the disc/drum valve. I'll post the results here.
