Rear Disc Conversion and Proportioning Valve

[ZombieK5]

I purchased the Lugnut from the 4x4 rear disc kit but haven't installed yet. As I tear into the Blazer I am finding strange stuff. This looks like a traditional Brake Booster with attached Master Cylinder. Below it is one (maybe two - hard to tell) aluminum block(s) that seems to be a proportioning valve.

Down near the frame there seems to be a splitter valve. It is fed from the "proportioning valve" and splits two ways. One feed line to each front caliper. I've never seen this. I'd expect that the feed lines to each caliper would have a dedicated connection to the master cylinder or proportioning valve. Haven't seen this setup.

Modern ABS systems use the ABS valve to proportion breaking. I can't remember what. These old school vehicles had.

Ideas or identification??

Recommendations??

 

[sweetk30]

upper stuff has rear wheel abs . you can ditch that and the black box thats hanging with it .

front valve unit is the abs specific prop valve note the lines from the master to it then out to the other areas .

down by p/s pump is the TEE for the front lines . its fine this way as thats all a reg prop valve does on the front end .

i have done in the past ditch all stock stuff for prop valves . then install this only on rear line and few test drives and adjust to your liking and good to go . you need 1/8" pipe thread to 1/4" double 45* adapters . the ones in the kit are for 3/16" line . https://www.summitracing.com/parts/sum-g3905

if you want to redo the whole setup and have a cleaner look i have this one on a truck now and no problems . https://www.summitracing.com/parts/sum-g3906 . its got the 2 line front out and 1 rear out with adjuster built in . the switch is only for brake lights NOT the warning in the dash .

 

[ZombieK5]

upper stuff has rear wheel abs . you can ditch that and the black box thats hanging with it .

front valve unit is the abs specific prop valve note the lines from the master to it then out to the other areas .

down by p/s pump is the TEE for the front lines . its fine this way as thats all a reg prop valve does on the front end .

i have done in the past ditch all stock stuff for prop valves . then install this only on rear line and few test drives and adjust to your liking and good to go . you need 1/8" pipe thread to 1/4" double 45* adapters . the ones in the kit are for 3/16" line . https://www.summitracing.com/parts/sum-g3905

if you want to redo the whole setup and have a cleaner look i have this one on a truck now and no problems . https://www.summitracing.com/parts/sum-g3906 . its got the 2 line front out and 1 rear out with adjuster built in . the switch is only for brake lights NOT the warning in the dash .

I plan to ReDo the WHOLE thing.

I havent looked to see if you have a build page (driving in rush hour traffic) but do you have photos of your setup? No idea why there is an ABS style valve on my 77 K5. This is a true Frankenstein.

How did you run the lines to the back? Did you use hard steel lines?

 

[sweetk30]

In my sig line click the BUDGET BEATER for the full unit .

I ran hard line like stock . I swapped to left frame rail for rear line and hose . Wish i had not as its made it harder for tail pipe routing .

 

[Wes Harden]

Looks like your truck was rebodied, I bet if you compare frame vin to body vin they are different. I didnt see a sensor on the 14 bolt so that RWAL system isn't working anyway.

 

[ZombieK5]

I have been meaning to confirm the frame VIN.

The bracket you had in your photo for the valve, did you fabricate that or is it available thru Summit or another source?

The other valve (SUM-G3905)...did you install that also or was that a previous idea?

I'm planning on keeping the master cylinder unless I find one that has a nicer look or visual appeal

 

[sweetk30]

i have used both now . if not a full replumb i use the first one for rear line only .

 

[Gentleman Jimmy]

You could also use CPP pn# PV-24 BH. It’s a prop valve designed for an all disc brake application no adjustment necessary . Bolts right to the frame just like the factory one, and retains the dash warning light switch. Make sure you get the prop valve tool as well so you can bleed the rears properly. CPP has one of those too (PV-TOOL) but can also be found elsewhere, definitely worth the 5-10 bucks.

 

[nvrenuf]

Proportioning valves are overrated.

 

[skunked]

Since you plan on redoing the brake lines, another option is the wilwood splitter (splits the front brake lines) with a built in adjustable proportioning valve for the rear along with a light switch. I went with this option on my 84 K10.

Pardon Our Interruption

 

[Gentleman Jimmy]

Proportioning valves are overrated.

Lol.. might as well run a single reservoir master too then.
prop valve saved my a$$ when I blew a seal on my rear caliper. Valve closed the rear line off as it should when there’s a 10 psi differential and was able to get me home on the front brakes without any major issues.

 

[sweetk30]

Since you plan on redoing the brake lines, another option is the wilwood splitter (splits the front brake lines) with a built in adjustable proportioning valve for the rear along with a light switch. I went with this option on my 84 K10.

Pardon Our Interruption

Already linked that for him . Just summit version for less money .

 

[skunked]

Already linked that for him . Just summit version for less money .

My suggestion was based on my personal experience with that specific wilwood product.

 

[ZombieK5]

Soooooo many options. Well, the whole shabang is going. Keeping the Booster, looks almost new.

Trashing the lines, master cylinder, splitters and whatever else there is. Def need a proportioning valve though

 

[sweetk30]

goo the summit i linked or full price willwood linked .

 

[doubletrouble]

I’m running the Wilwood.