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Thread: 85 CJ7 - Manual to Power Brake Conversion Question

  1. #1

    Icon5a 85 CJ7 - Manual to Power Brake Conversion Question

    HELP!
    I just got my first Jeep, an 85' CJ7 (see it if you care- http://members.cox.net/scott.rule/jeep.htm ), the first thing I want to do is add power brakes (current system is manual (2 line), front disk, rear drum). I just purchased a power brake kit from Orielly's which came with a booster and the master cylinder, it appears the bolts on the booster do not match up exactly with the 4 (unused) bolts currently on my firewall and I might need to drill new holes (they are only off by about 1/2 inch each way so drilling will still put the new holes in the firewall into supported metal. I asked the part guy and he said that I definateyl have the correct part.
    Can anyone tell me if they have doen this conversion and did you have to drill new noles?
    Scott
    85 CJ7 Owner

  2. #2
    Registered ChiliPepperTJ's Avatar
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    I have never heard of that conversion but I have helped with at least 3 YJ brake booster/MC conversions. I plan on upgrading my factory power brakes to yj pb's also in the near future. Check out the writeup that Brian did:

    http://www.jeepsunlimited.com/module...article&sid=80


    BTW there are a set of holes in the firewall and there is also a set in the metal inside the tub that attaches to the pedal assembly. They move independently from each other when you removed the factory manual brakes. Try putting a tapered awe into the hole from inside the tub to the firewall to help align the rest of the holes, you may need 2 people to do it. We ran into that with the yj pb,s and that worked with it every time, we never drilled new holes.
    Kevin
    '84 CJ-7 Renegade- 258 GM TBI with spark control and HEI, t-5, d300, d30 w/aussie locker, amc20 w/ trac loc, 33" Swamper SSR's, 2.5" BDS, 1" BL, MORE shackles, Superwinch hubs, Superior shafts, tie-rod flip, Taurus Fan, YJ brake booster, Full cage, A to Z rocker guards, A to Z rear cage, lots of other stuff...
    '05 Tahoe LS 5.3 flex fuel, Z55, Cooper AT3's, K&N fipk, G80 locker, HD Hood, z71 fogs daily, driver/kid hauler
    Sold: 98 TJ, 96 ZJ, 00 WJ, 02 WJ
    My Junkyard TBI writeup: http://www.viciouscustoms.com/TBI/junkyardtbi.asp.htm

  3. #3

    Default proportioning valve

    Hum.....after looking at the link, it looks like what I am missing is a "firewall adapter" (spacer at back of the booster) the holes for it probably line up correctly with the firewall and the booster!
    Does anyone know if I would need a "propotioning valve", it seems to me that since my master cylinder is a multi-chamber cylinder and so is the one I am putting on, that I would not need to do anything.
    85 CJ7 Owner

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    Is it still too late to send it back?

    I've also done the YJ booster mod that Kevin is talking about... It's great and it's cheap... If there is such a thing as too much brake, I've got it... And did I mention it's cheap?

    Make sure you snag the combination valve, [carl]Some call it a proportioning valve, I call it a combination valve, mmm hmm[/carl], booster to firewall bracket, and maybe even the first few feet of the brake lines out of the valve for simplicity's sake...

    Oh, and to answer your question, yes, you will still need the valve, regardless of which system you use... Your CJ should already have one on the framerail that might be able to be reused with either setup... I just elected to go with the YJ valve...

    Good luck!!
    75 years and 350,000 miles of fun:

    1983 CJ-7 No maintenance, just mods

    1998 M3/4/5 No mods, just maintenance

    1983 R65LS No intention of modding it, don't know how to maintain it


  5. #5

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    I guess I will take it back and do the same upgrade everyone else is doing, thanks!
    85 CJ7 Owner

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    -=- originally posted by sdrule -=-
    I guess I will take it back and do the same upgrade everyone else is doing, thanks!

    Not to talk you into being a sheep or something, but it's a nice little junkyard upgrade...
    75 years and 350,000 miles of fun:

    1983 CJ-7 No maintenance, just mods

    1998 M3/4/5 No mods, just maintenance

    1983 R65LS No intention of modding it, don't know how to maintain it


  7. #7
    Registered oldstyle's Avatar
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    So has anyone tried the YJ m/c with 4 wheel disks? Does it push enough fluid?
    David's Law: Nothing is easy. Everything is a project.

    '80 CJ7- owned 23 years, built oldstyle with AMC 360, T-18, Scout axles.

    Salvage/rebuilt 2006 Wrangler Unlimited 4.0, auto, and COLD A/C!

    This one died so others may may live!

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    Registered ChiliPepperTJ's Avatar
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    I am definitely doing the yj booster, and am leaning to rear disks, I'm just a little nervous about cutting up the backing plates for the amc 20 since they are hard to come by. I am thinking about pieceng that together this winter.

    For the proportioning valve, I have seen it both ways with the yj booster mc. by both ways I have seen the factory onw used that was for manual brakes and I have seen that one removed and a yj one put in place. They yj prop valve is more work though.
    Kevin
    '84 CJ-7 Renegade- 258 GM TBI with spark control and HEI, t-5, d300, d30 w/aussie locker, amc20 w/ trac loc, 33" Swamper SSR's, 2.5" BDS, 1" BL, MORE shackles, Superwinch hubs, Superior shafts, tie-rod flip, Taurus Fan, YJ brake booster, Full cage, A to Z rocker guards, A to Z rear cage, lots of other stuff...
    '05 Tahoe LS 5.3 flex fuel, Z55, Cooper AT3's, K&N fipk, G80 locker, HD Hood, z71 fogs daily, driver/kid hauler
    Sold: 98 TJ, 96 ZJ, 00 WJ, 02 WJ
    My Junkyard TBI writeup: http://www.viciouscustoms.com/TBI/junkyardtbi.asp.htm

  9. #9
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    -=- originally posted by ChiliPepperTJ -=-
    For the proportioning valve, I have seen it both ways with the yj booster mc. by both ways I have seen the factory onw used that was for manual brakes and I have seen that one removed and a yj one put in place. They yj prop valve is more work though.
    Kevin
    Either valve should do roughly the same thing, I would think... Let's put it this way... 4WDH doesn't list separate parts for power and manual brakes, so I would assume there's no difference...

    I like using the YJ piece because it gets the valve off the framerail... One less thing covered in mud, dunked in creeks, etc...

    -=-originally posted by oldstyle-=-
    So has anyone tried the YJ m/c with 4 wheel disks? Does it push enough fluid?
    If you go to rear discs, you should check out an adjustable proportioning valve... Note that this is not the same thing as a combination valve... It won't tell you if you have air in the system, etc...
    75 years and 350,000 miles of fun:

    1983 CJ-7 No maintenance, just mods

    1998 M3/4/5 No mods, just maintenance

    1983 R65LS No intention of modding it, don't know how to maintain it


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