Robzzzz Posted October 21, 2011 Share Posted October 21, 2011 (edited) So I bought this rust bucket 240 that had a small block chevy and saginaw 4 speed and I took the rear disk brakes off of it [it had rear disk brakes]and I put them on a relatively straight and rust free 280 chassis , so my question is regarding plumbing changes from drum to disk , I figured I might remove the proportioning valve and conect the passenger front line together where it enters and exits the valve,then install a adjustable proportioning valve in the rear line in place of the original valve, and is there a residual pressure valve that should be removed ? I have done disk conversions before and always had to remove the residual pressure valve or the rear would lock up and not release , if there is one that I have to remove ........where is it ? Edited October 21, 2011 by bobzzzz Quote Link to comment Share on other sites More sharing options...
Jethro Posted October 21, 2011 Share Posted October 21, 2011 So I bought this rust bucket 240 that had a small block chevy and saginaw 4 speed and I took the rear disk brakes off of it [it had rear disk brakes]and I put them on a relatively straight and rust free 280 chassis , so my question is regarding plumbing changes from drum to disk , I figured I might remove the proportioning valve and conect the passenger front line together where it enters and exits the valve,then install a adjustable proportioning valve in the rear line in place of the original valve, and is there a residual pressure valve that should be removed ? I have done disk conversions before and always had to remove the residual pressure valve or the rear would lock up and not release , if there is one that I have to remove ........where is it ? Looking at the FSM (download from http://www.xenons30.com) there is what they are calling a "check valve assembly" in the rear outlet of the master cylinder. My guess is that this valve serves as the residual pressure valve since it's in the typical location for one. Maybe someone can verify this? Your plan for the proportioning valve looks like the right way to do it. Quote Link to comment Share on other sites More sharing options...
Robzzzz Posted October 21, 2011 Author Share Posted October 21, 2011 (edited) Thanks for the link , lots of good info there . I didnt find the diagram there but I did look at one I have and it shows check valves on both outlets so it left me scratching my head , I have done alot of reading on Z rear disk conversions but cant find any reference to the residual pressure valve all the info I find is on calipers and rotors but not much on hydraulics. Did people just skip dealing with the residual valve ? without any problems ? Edited October 21, 2011 by bobzzzz Quote Link to comment Share on other sites More sharing options...
Jethro Posted October 22, 2011 Share Posted October 22, 2011 Thanks for the link , lots of good info there . I didnt find the diagram there but I did look at one I have and it shows check valves on both outlets so it left me scratching my head , I have done alot of reading on Z rear disk conversions but cant find any reference to the residual pressure valve all the info I find is on calipers and rotors but not much on hydraulics. Did people just skip dealing with the residual valve ? without any problems ? My plan was to use the Wilwood 1" MC that was referenced on the sticky for this folder. The recommendation for this MC is to remove the residual pressure valve for disc brakes. Quote Link to comment Share on other sites More sharing options...
Robzzzz Posted October 22, 2011 Author Share Posted October 22, 2011 (edited) I finished the passenger front line yesterday and I am still trying to figure out how I am going to connect the adjustable proportioning valve since it has 1/8 npt on the valve and I have read that the lines are 10mm-1.25 but I also read they are 10mm-1.0 , I cant seem to find a addaptor fitting to put it together so if I cant find them I will have to either see if I can find pre made lines with different fittings on each end or I may have to cut and flare , my only other option I can think of is to re do the line all the way to the back and swich to "AN" fittings at the end of the hard lines .anybody have any sugestions ? and can someone confirm the line size of 10mm-1.25 or 10mm-1.0 , I'm heading to napa to see if they have lines with different ends metric at one standard at the other , or if they by chance have the fittings , they make them in almost every other size . Still have not found a answer about the residual valve , I have a couple MCs so I might try to see if I can swap the rear check valve for a front check valve from another MC , drums need more residual pressure than disks so I would think they would have different pressure ratings , anyone have info ? Edited October 22, 2011 by bobzzzz Quote Link to comment Share on other sites More sharing options...
beermanpete Posted October 23, 2011 Share Posted October 23, 2011 The brake line fittings are M10x1.0. The residual check valve is in the master cylinder. Take of the adapter fitting that the brake line attaches to. You should be able to remove the internal parts in there and put the adapter fitting back on to eleminate the residual pressure function. Quote Link to comment Share on other sites More sharing options...
Robzzzz Posted October 23, 2011 Author Share Posted October 23, 2011 (edited) Beermanpete thank you for the info , that is prety much what I was thinking to do to the valve , the thing that confused me was when I looked at the mc diagram it shows check valves on front and rear , I didnt think they used the check valves on disk unless the mc sits lower than the calipers [floor mount] anyway I was thinking swaping in the front valve from another mc with the rear valve of the mc I am using so the rear output would have a front disk valve , overkill ? did you remove the valve ? Edited October 23, 2011 by bobzzzz Quote Link to comment Share on other sites More sharing options...
Robzzzz Posted October 26, 2011 Author Share Posted October 26, 2011 Has anybody allready done a disk conversion with a modified stock M/C ? If I cant find someone who allready did it then I am just going to remove the M/C check valve on the rear output . Quote Link to comment Share on other sites More sharing options...
Robzzzz Posted October 29, 2011 Author Share Posted October 29, 2011 I think I may have got lucky , the rust bucket 240z I'm striping might have a zx master cylinder , anyone have any pics or way to ID , I know its a nabco and it is 15/16 so I want to confirm if its allready set up for rear disks , I think its the right one but just want to try to be sure before I swap it over. I will try to post a pick Quote Link to comment Share on other sites More sharing options...
ritrebor Posted October 30, 2011 Share Posted October 30, 2011 I think I may have got lucky , the rust bucket 240z I'm striping might have a zx master cylinder , anyone have any pics or way to ID , I know its a nabco and it is 15/16 so I want to confirm if its allready set up for rear disks , I think its the right one but just want to try to be sure before I swap it over. I will try to post a pick If it says 15/16 and it bolts up to the booster it's the right one. Mounting tabs should be vertical instead of horizontal. ritrebor Quote Link to comment Share on other sites More sharing options...
Robzzzz Posted October 30, 2011 Author Share Posted October 30, 2011 Cool .... I have the right one ! One less part to buy , now on to plumbing the adjustable proportioning valve . Quote Link to comment Share on other sites More sharing options...
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