89RsPower!

after looking closer at the pic im dead wrong, that's kinda in the right area though, except its on the side of the housing, and like said above has a plug in it with a square-cut hole for a 3/8th ratchet or extension to fit into.

ZR1-IROC-RS

Breather hole? What the hell is a breather hole? I've been pouring gear oil into it for the past half an hour. It opens into the diff and axle shaft...and it's taken almost 2 quarts so far. That's what got identified as the filler hole without a plug....

Breather valve...ok...now to hunt for the square peg in a round hole

ZR1-IROC-RS

Lookee what I found......

Now, for damage control....do I just pull the plug and drain whatever excess drips out with the diff perfectly level?

As for this breather valve...do I need one?
is it something that should be there at this point?
Is it connected to the rest of the car I mean?

At this point (with the diff refilled) I notice that the rear spins, but doesn't seem to spin as freely as my car jacked up in neutral, should they spin freely like the open rear I have in the car (also to note I haven't removed the rusted calipers/rusted over rotors yet so that might be the resistance I'm feeling)?

89RsPower!

with the rear installed in the car, or sitting on a bench the way it would be in the car, remove the differential cover to drain the fluid, clean surface's and replace old gasket and reinstall the diff cover, remove the fill plug, fill with the correct weight gear lube til it just starts to weap out of the fill hole, reinstall plug.
The breather, yes you should have one in there but since you're swapping it into ur car chances are there is already one on your car, simply use that one when u do the swap. I wouldn't worry about it with the diff out of the car just make sure its installed before you go off driving, it doesn't tie into anything in the rest of the car per say but IIRC it has a little hose off of it that goes to something above the rear and vents there (probably to keep water from going in if you were to drive over a deep puddle)
Don't worry about it being hard to turn if it has rusted brake components on it.. remove the calipers and rotors and try turning the yoke, it should turn pretty easily.

89RsPower!

Ah I just reread what you wrote, you already filled it. Ok no big deal, when u install it into the car just remove the fill plug and top it off until it just starts to weap out of the hole. It should take about 1 3/4ths quarts

ZR1-IROC-RS

Yes, that's the general procedure I'm following...but I've already resealed the diff. and filled the fluid through the breather hole (I'm sure I may have overfilled it now but I digress. I have it leveled presently on two jack stands with the yoke leveled by a raise. It is presently as if it were in the car.

With the overfill situation, gaskets already been replaced, bolts are all torqued to spec and fluid is in, the only problem I have right now that I can see is that the fluid is likely overfilled since the breather hole was misidentified and confirmed as the filler hole....I would prefer to just pull the drain plug and drain out the excess at this point and not go through breaking it all down again. Is there any reason that shouldn't be just fine?

I figured salvage from the existing rear was an option. Planning an odds and end junk yard trip shortly so if I see one I'll grab it, otherwise salvage will be the option. Apparently I can get it from GM for like 3-4 bucks so no biggie either way...does it just pull out then?

I wasn't too concerned about it, but once I finish the diff portion of the rebuild I'd like to "set it and forget it", I'm pulling the calipers/rotors later today after the diff. redrain., and hopefully the existing shocks which I think I'd rather keep the new ones I installed over the summer, just more confident in them. Any difference between v8 and v6 rear shocks I should consider?

And so, back to the brake proportioning discussion then......rear pressure needs to drop going from drums to discs and the adjustable valve sounds more flexible in the long run as far as accounting for any other non stock changes that I do to the car....and is a $30-50 option and the stock fixed valve is a $70 option....anyone want to speak up as to why I should go the 'stock valve' route instead of adjustable?

Piece by piece the rear is almost serviced

ZR1-IROC-RS

Sweet, since I put in almost 2 it doesn't sound like I overfilled it too badly...do I have to do it in the car? (just easier to work on standing up than on my back, and I used a bulb level to square the x,y,z unless the yoke should be tipped up but I can adjust it still if neccessary) still going to clean and paint

five7kid

iTrader: (14)

Doesn't matter whether it's installed or on the jack stands as long as it's mostly level. The fill level isn't a critical thing, with overfull generally being a little less desirable than slightly under full.

ZR1-IROC-RS

Good deal...I figured as much, but affirmation is much appreciated.

ZR1-IROC-RS

ok, so I'm going to pull the drain plug, level off the fluid and pull the shocks/calipers this afternoon....hoping to have this changeover ready for the beginning of next week (Spring break for me) and to finish it by the end of the week...the current consideration being back to the brake system and the adjustable valve confusion....the quote above is where I left off on the brake system conversation and the questions are still outstanding. So can anyone explain which one of those would be compatible (if any) with presumably stock brake lines?

ACCLR8N

iTrader: (8)

You are going to have to cut the existing rear brake line, buy some tube nuts that will fit over the 6mm line, 1/4" will do and flare the ends to go into your valve. You can ignore the 14mm x 1.5mm thread pitch fitting in the proportioning valve as it will go back where it is after you remove it for cutting and flaring.

I don't see any 3/8 or 10mm tube nuts that will fit over the existing line. Looks like a pair of adapters will be needed as well. Suprised none of the valves accept larger fittings. I hate plumbing. The 10mm x 1.0 is the largest in your list.

ZR1-IROC-RS

Cut?...umm...yikes...sounds like I could mess that up kind of easily...I snapped a pick of the existing for a common point of reference, I labelled it as I could (though please check for accuracy).

Tube nut, what's a tube nut? Flaring, do I need a special tool for that?

ok...these are metal lines and it looks like the rear line is on top towards the firewall...is there any other way to connect an adjustable without hacking apart the existing lines (I was thinking some kind of bolt-in scenario with maybe a little piece of extra line before the valve)?

The list up there are the adjustable valve options off of summit's website...should I look for an adjustable prop 14mm X 1.5, can the threading be confirmed or are you sure it's that for the 91 RS?......I'm feeling a little overwhelmed plumbing too.

ZR1-IROC-RS

Ok...the axle is fully broken down. Diff leveled off, Calipers, rotors, shocks, all pulled. A little cleaning and it's ready for paint...the rotors are horribly rusted over and I had to hammer them off the axles (so the inner edges are now dinged up, but they were seized on there so they weren't coming off otherwise) but it looks like there is plenty of meat left and they aren't scored (other than my hammer marks), do you think it's worth turning them down with 2 years of rust on them?

89RsPower!

Don't be intimidated if you have to cut and flare the lines, it's really not hard at all. You will need a tubing flare tool, and it will probably come with a tubing cutter to cut the lines, if not you need a tubing cutter too. Basically all you do is cut the line with the tubing cutter, file the end to a slight taper, put your tube nut over it, then flare the end using the flare tool. Here is one from summit to get an idea of how it works, you clamp the line into the thing with the holes in it and then put the little press with the cone over top of it and tighten it down. The little dies are used for a double flare. http://store.summitracing.com/partde...5&autoview=sku
Wouldn't it be easier to just get a prop valve for an 86 maro with 4 wheel discs?

If you can turn the rotors yourself then I'd say go for it and see if they clean up, then measure em and see if you have enough meat left on em, if not toss em and get new ones. If you have to pay someone to do it you'd probably spend just as much money buying replacements so it should be a simple choice.

ZR1-IROC-RS

I think I'm going to try it...Easier to by the oem part, yes...and expensive to buy new, nearly impossible to find used (at least around here, in the yards I've got around I couldn't find a disc brake rear to begin with so I've never found a valve),...I've reasoned that adjustable gives me flexibility to adjust as the weight changes as I do different things and swap the engine I can adjust for aftermarket parts if I upsize rotors, change from stock tires, etc. and it looks like I can put in an adjustable for about ~$50 as opposed to the $125-ish for a stock combo valve....in the long run (once I learn to adjust it properly) I think it will be the overall safer option to be able to curve the brake system around any changes

I don't have the equip to turn them myself, so I'd have to pay someone...in that case I might just replace them outright...axle painting today in this beautiful weather!!!..., I will post picks after it dries.

ZR1-IROC-RS

Out of question...since these lines are already in place in the car (filled with fluid) can I just stuff them up with something (any recommendations) while I cut and flare and insert the valve? (I think I'm going to install it before the rear end goes in so it's in place when I do rather than do both at the same time and after installing the discs I can just adjust the valve rather then install it)

How does this sound for the procedure:

1.Pop the top on the Master Cylinder to relieve the system pressure
2.Cut and stuff lines
3.Nut and flare the outgoing line (identified in the image as the 'Rear line') then restuff.
4.Nut and flare the incoming line (into the valve)
5.Close the valve completely after gravity bleeding through the output port
6.Attached the incoming line (do I need o-rings? ft-lbs.?)
7.Attach the outgoing line.
8.Open the valve completely
9.Bleed the rear drums(do I need to do this?or will it just bubble back up into the MC?)
10.Top off the MC

ACCLR8N

iTrader: (8)

The rear brake line is the "front small" bellow the "MC-1" in your picture, not the one you have labled as "Large Rear".

Don't worry about stuffing anything in the lines. Be sure the section you are cutting and flaring is clean. The fluid leaking out will only help keep the crud out. Don't worry about closing the valve either. No O-rings are needed with the flares. Don't have ft-lbs number for you but you are snugging them down with hand wrenches. No grunting or deforming the nuts, that would be too hard.

After you have re-flaired at least one end because you forgot the tube nut or put it on backwards and have bled first the passenger, then the driver side rear caliper check for leaks. When you find a leak, loosen the fitting a turn or two and re-tighten it down, 4 cycles of this will form the flair to the valve cone. Don't just keep trying to make it tighter.

ZR1-IROC-RS

Ok...that's good to know (I'll visually trace the lines before I do any cutting, I presumed the larger one went to the rear because a larger line would carry twice as much fluid and then split at the T connector). Why would one large line and one small line go to each of the fronts and then a small line go to the rear......seems like it would defy logic...

Sweet.

Are we guessing that I'll screw it up?

That's good to know...I probably would have just kept tightening and tightening until I broke or stripped it

ACCLR8N

iTrader: (8)

Sorry about that, not fair to assume everyone does things the way I do.

I'm very certain that the forward bottom port must be routed to the rear brakes. You'll notice it gets its own larger feed from the master cylinder to compensate for the large amount of line and two calipers/drum cylinders to pressurize. The rear half of the p-valve has two smaller outputs for the individual front brake lines. Check your routing, a previous owner may have routed it incorrectly thinking back of valve, back of car.

Pop the hood on somebody elses car for your personal conformation. Doesn't even have to be an f-body.

ZR1-IROC-RS

I thought it was funny (and not horribly unlikely )

Visual inspection confirmed the line routing and you are correct the front bottom port is headed for the rear.

ok, so I'm ordering the least expensive prop valve I can find with tube nuts today. I'm going to get the cutter and flare on loan from autozone. Today's goal is to get the calipers stripped and painted.

btw, Happy St. Patrick's Day everyone!!

ZR1-IROC-RS

Ok, so here's the choices:

http://store.summitracing.com/partde...5&autoview=sku

http://store.summitracing.com/partde...5&autoview=sku

http://store.summitracing.com/partde...5&autoview=sku

http://store.summitracing.com/partde...5&autoview=sku

Is there really any difference between these parts other than price?

ACCLR8N

iTrader: (8)

Me, I'd get the cheaper Summit proportioning valve.

I can't find an option through Summit that gets you from the 1/8 NPT to your 6mm brake line. These guys in PA were the only place I ever found that had my 14mm x 1.5 flare for 6mm line tube nut (three for $10 shipped in two days). They have an ebay store. I bet they can hook you. If you have a choice get the metric bubble flare tool from Autozone and bubble flare tube nuts. I find those easier to make and seal. Put a drop of oil on the flaring part of the tool.

autopartsmart@yahoo.com
Kevin-AutopartSmart
814-362-3221
8am-5pm
Eastern Time

ZR1-IROC-RS

Ok, so I get the $35 valve from summit, rent the metric bubble flare tool and buy the tube nuts at autozone or...

Get the $35 summit valve, order the tube nuts through the guy above, and rent an english flare tool from autozone..

ZR1-IROC-RS

So...everything I've been reading warns against connecting proportioning valves in series due to unexpected operation...especially when dealing with a factory valve...

So...I've been thinking about the whole plumbing part of things and is there any reason I couldn't just remove the factory prop valve all together, connect the two front lines to one master cylinder output via a 'Y' connector (unregulated as I understand the existing combo valve does), and put the adjustable valve on the other master cylinder output direct to the rear line? (possibly even without cutting things, maybe just some adapters)

five7kid

iTrader: (14)

Or, front master cylinder outlet to line lock inlet, two front lines to line lock outlet.

ZR1-IROC-RS

What line lock? Is that technical name for the 'Y' connector I referenced?

ZR1-IROC-RS

Ok...found out what a line lock is....and for fun street use, it'd be way over the edge...if I ever start doing serious drag in the car then I can put in a line lock pretty easily with the rear adj. prop- front 'Y' connector setup just by swapping out the 'Y' connector for the lock...for now (the present goal is the 4 wheel disc conversion/driveline/suspension upgrades for the sbc 350 swap) I think I can put that idea on the shelf of "differences between my car and a dedicated drag car"

...but the setup I'm talking about, rear adj. prop. valve - front 'Y' connector to eliminate the factory prop valve all together, can anyone think of any reasons I shouldn't do this? can't do this? wouldn't want to do this?

ZR1-IROC-RS

Now to find the right parts...according to Napa Online, if purchasing a remanufactured Master Cylinder (OE), the threadings listed are "Line Thread Size:M11 X 1.5; M12 X 1.0"
Are these sizes compatible with eachother or does each port have a different size? Can anyone confirm stock tube nut threading sizes (I need to know all 5 of the prop valve threadings, haven't been able to find a replacement prop valve that listed the port threadings)?

89RsPower!

Both are different sizes as you just stated.

ZR1-IROC-RS

ok...so can anyone confirm/report the stock prop valve port thread sizes?

ZR1-IROC-RS

So the rear end rebuild/repaint is complete (just have to put the e-brake levers back on)...posted pics for all's enjoyment. Chrome diff. cover Gloss black housing. Emerald green calipers and bar. Shiny turned rotors. ahh...it's pretty and I can't wait to put it in...so now the immediate and heavy priority is the brake system modification before I can install this lovely reworked 87 disc rear. So anybody have thread sizes for a stock drum/disc prop valve?

ZR1-IROC-RS

Ok, moot point on the prop valve threads. If I remove the factory prop from the system then I lose the pressure failure sensor.
(albeit an unimportant idiot light, but it'd be like having a doorbell that didn't work even though I can see a car pull up and knocking on the door works just fine)

So the next option...I spent some time in the 'Brakes' forum and apparently these issues/questions have come up in rear disc conversions before...shocking...it looks like I will have to gut the factory prop valve (which I'm considering grabbing one out of a junk yard for like $5 to do this prior to install and not disable my car while I work this out, create the bolt in assembly then change it out over an hour then spend the rest of the day adjusting it) to save the sensor by removing the spring and plunger and stopping it with a 5/8" plug...sensor saved, no proportioning from the OE pv and I can safely install the adjustable pv (Wilwood is apparently recommended) inline after the OE prop.

I believe this will accomodate all brake system requirements/functionality and provide me the adjustabilty I'll want as I make further vehicle changes...does this plan sit with everyone? Can anyone think of any reason not to do this this way?

five7kid

iTrader: (14)

Even if you bought a new proportioning valve (combination valve), you'd have to gut the check valve. Ask me how I know.

I'm going with a disk/disk master cylinder as well. Different size pistons vs. disk/drum.

The adjustable proportioning valve is really optional. And, probably not needed.

ZR1-IROC-RS

Well, that's why I figured, buy a junkyard one cheap or in pocket, I can cut/collect all the surrounding lines for 'raw materials' for any fab work. I planned on gutting it to avoid any conflict with an upline adj. rear prop. But I'm going on reading, info gathering and advice...so, how do you know?

I was under the impression that drums took more hydraulic pressure than calipers to operate. I'm going to an '87 rear w/ iron calipers (high volume, more pressure requirements)...I considered the MC change, but with the inline adj. prop to dial rear pressure down already I didn't feel the MC change offered any notable system improvement from disc/drum to disc/disc (and because of the higher drum pressure requirement from the stock setup I understood the disc/drum MC actually provides more rear action than a disc/disc MC).

Explain please as the core principle of this modification...."discs take less pressure to work than drums, therefore the stock proportioning system will apply the higher drum pressure to the rear calipers without a brake system modification resulting in early rear wheel lockup and causing a loss of control under heavy braking conditions and/or inclement weather...a reduction of pressure to the rear calipers (adj. prop) is required to maintain safe braking capability under varied operating conditions"

...if this is not the case then I will need some rather indepth information as to why, as that seems to make sense to me.

five7kid

iTrader: (14)

Hydraulics operate on the principle of proportional areas. Assuming the pressure is the same, the force applied is proportional to the areas of the respective pistons. If you get a master cylinder for an '87 disk/disk application, it will all be properly balanced.

My car is older and has SAE lines, so finding the proper parts is a little more difficult (the majority of 3rd gens had metric lines, and therefore support for 3rd gen SAE parts is much less - although non-stock parts like line locks are SAE. . .).

And, I know about the combo valve gutting because I ordered a new one from Master Power Brakes, and the instructions for use with disk/disk says to gut it and put in a plug.

ZR1-IROC-RS

As far as how the hydraulics operate I've got those principles down. Granted, yes, if I replaced the master cylinder, power booster (maybe not this one), combo valve and front spindles/calipers/discs with that from the 87 disc/disc it would all be properly balance, BUT I will have essentially reverted my brake system to an 87 brake system $400+ later (which is known to have inherent issues per the brakes forum and kills my budget). Just swapping the MC doesn't make sense since the combo valve is different from drum to disc and from early to late years (at least they're listed as different part numbers)...so they must be stock matched from every caliper/rotor to combo/master to balance 'as GM intended it'.

What I have is 87 rear discs (iron calipers/J65), 91 front discs (aluminum calipers/1LE), 91 combo valve(1LE), 91 MC(1LE), & 91 power booster(1LE) with presently a v6 motor to be converted to a v8 (big weight change). So all of this leaves me with the idea that no factory combo valve can properly accommodate all of these X-factors or changes over time because I'll no longer have a factory setup unless I change over everything in the system to match factory specs. I believe an adjustable valve on the rear will allow me to adjust bias to account for all these variables at $50-$75 and safely run a non-stock setup.

[quote=five7kid;4091133]I keep seeing that as I shop for aftermarket prop valves...it looks like it will be a process of metric to sae to metric...not a bad thing, but enough reason I think to build a separate assembly outside of the vehicle then swap it in and set it/forget it.

So how did it recommend regulating the brake curve once the proportioning valve no longer performs any proportioning (which really makes it a glorified 'T' connector) ? I have to think that if all the disc/disc system needed to operate properly was the MC then there'd be no such things as a disc/disc prop valve.

ZR1-IROC-RS

So I chatted with the guy at the local hotrod shop and he believes the difference in requirements from rear drums to rear discs is so minor it's neglible...:???:

ZR1-IROC-RS

Wow...everybody has got a different opinion on this...went to chat with the pros...I called Baer directly. They're recommending the Combo valve gut/disable and adjustable prop valve install. They don't offer a kit so they weren't trying to sell me anything (meaning the info is just info and not a sales pitch)...so...

...after all the back and forth, the decision is made.

I'm going with Baer's recommendation (and my own previously surmised conclusion) of the combo valve disable with inline adjustable prop. install.

Here's the plan:

I'm going to find an 88-92 prop valve (same part numbers according to the brake forums) out of the junk yard cheap and cut it out with enough extra line and tube nuts to do any prefab I need.

I'm going to find the best deal I can get on a Wilwood **** style prop valve for the rear. (shopping now)

I'm going to build it up together as a swap in assembly for the existing combo valve with borrowed tools from Autozone.

Then I will swap in and dial the proper brake proportions for the drums now, and just adjust it later after the rear end upgrade and again after the engine swap.

Ready? Break!!

92RS_Ttop

iTrader: (3)

Any chance you could post up some pics showing the mods needed to the oem prop valve and the connections you'll be making to connect to the adjustable one? I'm looking at doing almost the exact same swap next winter to my 92 RS. I'll be either going with 1LE fronts/disc rears or the C4 front swap/disc rears, depending on the overall price.

ZR1-IROC-RS

Absolutely!! In fact I'm honored to be asked such a thing (though admittedly I'd have posted it anyways)...if this works out the way I want it to I'd be happy to offer up my fab work to the group as a whole. Keep an eye on this thread...I'm trying to doc every step of this engine upgrade and I'm in the prep stages right now...any help/input you could offer is greatly appreciated as I thrive on information and have no real experience with anything like this. I've considered the C4 front brake swap as well...but it's not required for my engine swap (although desirable later on), so it's in the "aftermarket performance" category for me (stage4), post sbc 350/t56 install. I had to upgrade the driveline to take the 350 motor 400hp, so the j65 rear was a target (performance stock rear)...the rear disc conversion for me is necessary to accommodate the j65 install to accommodate the motor. So I've reasoned......the locker was a bonus and so was the front suspension/steering. It's getting there, sure enough, piece by piece.

ACCLR8N

iTrader: (8)

Sounds like a good plan to me. GM has been driving me nuts with all their different fittings. My son's 94 STS had a line failure last week and I nearly ruined the ABS module as I figured out the caliper flex line end I matched (10mm) was different at the other end (11mm) discernable only with a pair of calipers.

ZR1-IROC-RS

Change once, accommodate many and always...do it once, do it right. My brake system will be ready for anything I want to do to the car after this plan. I have confidence in it, and tomorrow it's supposed to be 60 degrees, so I'm going boneyarding

92RS_Ttop

iTrader: (3)

I kinda figured you would, but it doesn't hurt to ask. I'm always willing to help out with any input/advice I feel is needed/warranted, but I won't just toss out something unless I'm completely sure of it or have already done it. So far, your swap is something I've researched, and plan on doing, but that's as far as I've gotten with it. Concentrating mainly on my own V8 swap right now.

ZR1-IROC-RS

We have the same motor (though I modified a higher flowing intake into mine) and practically the same car 91RS/92RS...we should work together as we have approximately the same goal in mind ...how's your prep work going?

ZR1-IROC-RS

Ok...an extremely successful junkyard run. T-Top bar, dome light assembly, passenger underdash panel & side panel, shift plate with intact ashtray cover, radio bracket and console face plate, rear windows brake light assembly, fender marker lenses, 2 power window switches, cigarette lighter, and...of course...the purpose of the trip, the 1LE combination valve (1990 series, identical to my 91) with a few feet of surrounding brake line and all the connecting tube nuts...

Step 1 complete.

92RS_Ttop

iTrader: (3)

Sounds like you had a great day at the yard. Right now on my swap, I'm waiting for the crank to come back from the machine shop so I can order the rebuild kit and start putting the engine together. I've been falling way behind lately on progress and hitting a lot of snags(getting sick, my truck nearly puked the trans on the last JY run, not enough time, etc). I'm on something of a limited time schedule because of the truck and the way PA's emissions laws are written. I'll try to get a thread started on my swap sometime here in the near future so I don't end up hijacking yours.

ZR1-IROC-RS

Sweet...I haven't decided on/found the new engine yet. Which one did you decide to go with and why?

ZR1-IROC-RS

Ok...so the combo valve/adj. prop valve assembly build. This will be my base reference pic (relabeled from the previous 'in vehicle' shot, hopefully this time it is labeled correctly)...I wil update and repost it with relevant info as I go (dimensional measurements, thread sizes, etc.) I've held off ordering the adj. prop as of yet thinking I'll also need to order various fittings and adapters.

Break down and cleanup will be this afternoon.

Now, I'm thinking the spring and plunger are accessed/removed through the rear brake side black **** and nut on the end of the valve. Is that correct with everyone?

ACCLR8N

iTrader: (8)

You'll need to take both ends out, front and back. Replace each with a plug so its just an empty manifold.

ZR1-IROC-RS

I was just wondering about that actually...
Here's the technical lowdown as I've found it.

What do you mean by plug? just a short bolt to thread into the hole? from the rear port I removed the plug, spring, o-ring, and a hollow pipe with what looks like a plastic seal on the end. in the front port i brass rod with a plastic disc at the bottom,do I remove that too?