I installed a 1" bore Master Cylinder I think is intended for a FJ80 but regardless any toyota 1" master will suffice.. All this does is make your pedal travel less annoying.
My stock MC has a bore of 13/16" and this is clearly marked on both Masters. The plumbing intakes is a bit dif on these two masters but nothing a lil bending and creativity wont overcome. They are direct bolt ups btw... no modding of booster.
Heres a shot of the new master cylinder and how i configured the manual load proportioning valve:
I just re-used brake line from the rear. You will end up with twp spare hardlines from the rear end. The short line between the T and pass side drum and the long line between the T and driver side drum...
I LEFT THE STOCK LSPV VALVE IN PLACE.. I found without the stock LSPV (just the manual LP valve) the rear brakes recieved TO MUCH PRESSURE and caused them to lock up far prematurely when you braked hard. This is a extremely dangerous attitude that I dont know how other people deal with. The FRONT tires should ALWAYS lock up before the rears.. or at any rate should lock up at about the same time as the rears AT LEAST... Rear tire lock = loss of directional control. Its not as serious at slow speeds but at highway speeds you will most likely end up rolling or in a ditch. Its SERIOUS.
I found in my research most folks that have done this swap only trailer and use the rigs offroad.. no highway use... so the safety issue is less of a concern for them... This is my daily driver. This upgrade is a safety and performance upgrade... I want it to be SAFE under ALL conditions so i reccomend NOT TO REMOVE THE STOCK LSPV... just configure it however you want to reduce as much pressure it can (lower rod down as far as possible) and then adjust brakes with the manual LP valve. ...
I didnt reduce mine down completely. I just left it bolted to stock location on my axle.. I only have a few inches of shackle lift so this works out fine for me. ADJUST ACCORDINGLY to your rig!
I used the short line from flex line to LSPV to inline the manual LP valve then used the short hard line from the axle T to drum ... make sense? probably not but regardless once u get these hard lines off you'll be able to figure something out that works =)
Heres what an OEM Load Sensing Proportioning Valve (LSPV) looks like:
*The line going from the LSPBV to the front T is NOT a return line. There is a second valve inside the LSPV called a BV (Bypass Valve). It is held shut by front brake line pressure. In the event the front brakes fail (lose pressure) this pressure valve opens due to no pressure holding it shut. This allows full pressure to the rear brakes 'bypassing' the load proportioning valve. This is a safety feature.
Most writeups mention removing the stock LSPV and pluggin this T at the pass side front wheel (as seen in elvotas writeup)... I found on MY truck the overall braking performance was bettered by NOT removing the LSPV and instead supplementing it with a MANUAL LP valve inline with the rear brakes (as see in the above picture).
Do whatever you want but I'd test your brake setup WITH THE LSPV in.. if you want then to remove it, remove it. Save yourself the headache of having to REINSTALL It like I did. =)
FYI here is the junction located behind the passanger front wheel of the braking lines.
The 90 is the Master Cylinder to LSPV line... The T... The line coming from the top is from the MC directly from the Front piston in the MC that goes to a T below the M (that separates Left from right front calipers)...
the left part of the T is the return line from the LSPV.. and the right side of the T goes to the passanger side FRONT caliper.
Most writeups replace that T or plug the pressure line to the LSPV (since its commonly removed).
I found in my installation (before reinstalling the LSPV) that it was next to impossible to find a coupler to MC to passanger side caliper lines... So I just stretched the MC to -T line to make it to the flex line that feeds the right passanger front caliper. there is PLENTY OF LINE to make this work on a truck with NO body lift. I have 2" of body lift so i got creative but its possible and SAFE to make it stretch. I would of had to get VERY Creative with that hard line if i had more than 2" of body lift.