Manual Disc conversion without Prop valve

[91r/t]

Hey all, so I have a 68 Runner with manual drums all the way around. I am starting to feel my drums get warped and am thinking it is time to upgrade to front discs. I can get the spindles, bearings, hardware, calipers, and rotors for $500.00. Seems like it's the time to do the swap. I am seeing a few of my buddies run a disc front and drum rear without a proportioning valve. I really don't wanna tear into the brake lines to modify for a prop valve so whats the opinion on here about running the manual discs without the prop valve? I have a manual drum master, but I will pop the residual valve out of the rear reservoir so it doesn't hold pressure against it like the drum system does. Whats your guys take of this that have done it?

 

[FrnkNsteen]

From what I have heard and read, you definitely want to run a proportioning valve to get them to work correctly. Give Dr. Diff a call and see what he suggests.

http://www.doctordiff.com/

 

[eddie102870]

just installed disc brakes on all four corners and replaced the master cylinder with one from SSBC. came with a proportioning valve but i didnt install it. brakes work fine.

 

[91r/t]

just installed disc brakes on all four corners and replaced the master cylinder with one from SSBC. came with a proportioning valve but i didnt install it. brakes work fine.

That is with 4 wheel discs though. I am reading drums take less pressure to activate then discs, so that is the problem with them locking up the rears before the fronts activate. I feel with the manual brakes I have a better shot at not locking them up and having more control.

 

[R/T Boy 67]

You should always use a disc master, with it's bigger resevoir. It is very important to get the front, rear, bias correct, especially if the road is slippery. You have to test the car to determine this. Plumbing in an adjustable prop valve is pretty simple.

 

[Billccm]

Brake bias is very important. Richard Ehrenburg had an excellent mopar action article a few months back explaining why brake bias is required in the conversion.
My recommendation is the Dr Diff kit.
I sympathize with you on the brake lines ordeal as I lived through that nightmare myself. Having said that I am happy with the results.

 

[NJRR]

You definitely have to change the master to a disc/drum master. I used a 15/16" master from right stuff and an adjustable prop valve, both from summit. It was very easy plumbing in the prop valve. It was just 2 ready made 30" brake lines into the distribution block and out to the rear line.

 

[65-440]

Installed front discs on my 68, also using disc/ drum master cylinder. No prop valve, no problems ... even under hard braking .....

 

[91r/t]

You definitely have to change the master to a disc/drum master. I used a 15/16" master from right stuff and an adjustable prop valve, both from summit. It was very easy plumbing in the prop valve. It was just 2 ready made 30" brake lines into the distribution block and out to the rear line.

View attachment 645271 View attachment 645272

Biggest thing with the disc master is the residual valve inside the housing for the drum application. I can remove that no problem. The bigger volume is nice, but I think I can get by with the small housing if I remove the valve from the front brake reservoir. My master is almost brand new so I was going to experiment. I see alot of the newer disc masters have equal housings with no problem. Being a manual brake car, it has the smaller 15/16" bore on it already, so it should have good pedal pressure as well.

 

[91r/t]

Just looked at the damn master on it is two diff sizes ......I was told it is a manual drum master, but at any rate I am going to check for the residual valves and if so, I will yank the front and use it.

 

[R/T Boy 67]

If your master is the original type it will have different size reservoirs. 1967 to 1970 drum masters were all like that. The front circuit was still pretty small for disc brakes. You will have to keep a close eye on the fluid level. The original bolt on cover masters had a 1 inch bore.

 

[beanhead]

Adding in a proportioning valve is no big deal...the proportioning valve needs to be in-line with the rear brake line, after the stock distribution block. Buy (or make) a short brake line with the proper fittings. Unhook the single line that runs to your rear brakes. Plug the short piece of line in where you unhooked the rear brake line, and then into one side of the prop valve. Your rear brake line then hooks into the other side of the prop valve. You can bend a loop in the line or whatever is necessary to make it all fit back together, no cutting/flaring needed

 

[NJRR]

Adding in a proportioning valve is no big deal...the proportioning valve needs to be in-line with the rear brake line, after the stock distribution block. Buy (or make) a short brake line with the proper fittings. Unhook the single line that runs to your rear brakes. Plug the short piece of line in where you unhooked the rear brake line, and then into one side of the prop valve. Your rear brake line then hooks into the other side of the prop valve. You can bend a loop in the line or whatever is necessary to make it all fit back together, no cutting/flaring needed

I used 2 30" ready made lines and did exactly what beanhead described, except instead of a short line I used a 30" line so I could mount the prop valve higher in the engine compartment for ease of adjusting rear brake bias. I then ran another 30" line down to where the rear brake line screwed into the distribution block and used a union to join the rear brake line to the 30" line from the prop valve. I had to make a couple of bends and loops to make it fit. It's one more joint and place to leak but made it easy to adjust.

 

[91r/t]

Hmmmm this must be a newer style because it has a big reservoir. It also has the snap over strap type so it doesn't have a bolt on cap. I will try and add the prop valve if needed by the stock distribution block because I want to keep the stock type look. My master looks like NJRR pictures above.

 

[NJRR]

Hmmmm this must be a newer style because it has a big reservoir. It also has the snap over strap type so it doesn't have a bolt on cap. I will try and add the prop valve if needed by the stock distribution block because I want to keep the stock type look. My master looks like NJRR pictures above.

I was debating about the stock look also but decided on ease of adjustment since the master and front disc setup wasn't original anyhow. I had to stop and adjust the prop valve at least ten times to get it where I wanted it and didn't feel like crawling under the car every time.

 

[91r/t]

I was debating about the stock look also but decided on ease of adjustment since the master and front disc setup wasn't original anyhow. I had to stop and adjust the prop valve at least ten times to get it where I wanted it and didn't feel like crawling under the car every time.

Awesome setup I really like it. it looks clean as hell, I am just an **** moron and want to hide it . I will probably run the stock style prop valve and that will have to do.

 

[NJRR]

Awesome setup I really like it. it looks clean as hell, I am just an **** moron and want to hide it . I will probably run the stock style prop valve and that will have to do.

The beauty of my setup is I can easily convert it back to the stock look and use an original style prop valve, which I might do down the road if I get motivated. I didn't cut or bend any of my original brake lines and the hole I used to mount the adjustable prop valve was already in the fender/wheel well.

 

[wagonman]

I used a Master from Ehrenberg and no prop valve on my disc front 11in drum non power conversion. Good pedal modulation but ya really got to lay into it to get them to lock up. Even in the rain it is hard to get the rears to loc and swap ends. Thank goodness.

 

[91r/t]

Now that I know that I can put a prop valve in place of the factory drum distribution block without modifying the brake lines, I will try it and if need be I will install the prop valve. Talked to Dr. Diff about the prop valve and he told me you can replace the block with the standard prop valve and no modifications are needed. I guess that answers my question then, no problems if needed.

 

[91r/t]

I used a Master from Ehrenberg and no prop valve on my disc front 11in drum non power conversion. Good pedal modulation but ya really got to lay into it to get them to lock up. Even in the rain it is hard to get the rears to loc and swap ends. Thank goodness.

Wagonman, how is the stopping power compared to the drums? Pretty grabby even though they are manual and not power assisted? I have never had a manual disc car, only power disc.