No conventional brake prop valves in any 88-91??

[Glen]

So is it a big deal or not?

[gadget73]

define "big deal", and what part you're after. Its not as good as it possibly could be, and for me thats a big deal. It does however work OK, so for most people its not a big deal, and I'd be willing to wager most folks wouldn't even realize its not optimized. I like to screw with things though, and I'm usually not entirely happy until I've fixed it beyond the point where its usable anymore.

[FatNasty]

Well, i was planning on replacing my master cylinder soon. Currently have stock 84 MC and prop. valve and lines. I have 97cv pi rear disk brakes. Will be putting in brand new stock front brakes. lI'd like to upgrade to a newer master cylinder, and use the appropriate new lines, and blocks. Basically the best scenario to work with disk front and rear brakes. What year/style prop. valves and lines, etc. should i be going with to provided the best performance for stock brakes, plus 97 rear disks? I'm Willing to replace all lines, just want best specific info i can get. Thanks mangs, Lay out my options:::

-Mark

[johnunit]

The chart from Gadget in post 15 is yet another reference to the illusive "grand marquis police". Interesting.

[Glen]

How will the car act in a panic stop? I have standard 89 disk on the front and disk from a 97 PI in the rear. I didn't change any prop. valves or master cyl. The car stops fine now. I have not locked up the brakes, so I don't know how it will act if I do. The big deal is what will happen if I do have to lock em up.

[gadget73]

The existing stuff will not cause the brakes to lock up in the back. At worst, they're cutting the rear line pressure down a bit lower than ideal so the rear brakes aren't doing as much as they could. The front brakes are grabbing slightly later than they could, which also slightly reduces overall braking capacity. Basically you're not going to kill yourself with the stock valving and rear discs, but there could be an improvement in performance with some valving tweaks.

Markus: later model MC is probably what you want, some mid-90s model with 4 wheel discs and no ABS. The later style booster is a dual diaphragm one too. I don't know how much actual improvement in boost that gives you, but its smaller in diameter if you need more firewall clearance for something. I'm thinking if you've got stock fronts and rear discs, the ideal setup would be the 92-94 non-abs stuff since those front brakes are the same diameter as the box front brakes and the rear discs are also the same as the 97. Those have the prop valve threaded right into the side of the master cylinder between the MC and the line down to the frame. The existing frame mounted valve would have to go away and be replaced with L blocks or unions or something if you used that setup though. I don't know what sort of thread is at the master cylinder end though. If its standard double flare, thats easy. If its wierdo metric BS, I don't know what the trick is unless you use a metric to standard adapter, or get your hands on whatever sort of bubble flare thing is used with metric brake line fittings. Its a double bubble or some crap like that. Not exactly the same as the double flare that is usually seen.


I really wish it was warmer outside. I want to go junkyarding for research, but they're calling for some massive amount of snow this weekend. Boo.

[FatNasty]

sounds like 92-94 mc is the way to go then. I'm sure i can find enough adapters or whatever to get it hooked up, the napa guys here have been able to find me about every brake fitting i've ever needed. Will i need a new brake booster though or will the 92-94 fit in the old one?

[Lincolnmania]

my car has been stopping flawlessly since the conversion in 2004........we are just looking to super fine tune the whole mess

[Glen]

So, when it is time to replace the MC I will go with a mid 90 and redo the lines. Is the mid 90 MC a bolt on (other than the lines) or do I have to make it fit? Sounds a plan to me.
If it snows this weekend I will go play in a parking lot just to see what happens.

[85crownHPP]

All the ones I looked at have a metric fitting in the MC mounted prop valve for the rear, and my p72's definitely was a bubble flare going into it.

[gadget73]

Will i need a new brake booster though or will the 92-94 fit in the old one?

I think the later MC requires the later booster, but I won't swear to that. Its supposed to be a direct fit other than the lines. I believe blaze86vic has one, and freshmeat installed one on his old wagon to allow clearance for a clutch cable. I don't know of anyone else who has done it, so you may want to look them up for more details. I haven't done so just yet.



My car does stop fine, so its not a matter of not having properly working brakes. I'm just looking to experiment to see if it can be made better. Research has me convinced that improvements are possible, however none of this has been put into practice so it may amount to a lot of work for no appreciable results.

[gadget73]

more reading. This is a disc brake swap on a 70s vintage 4x4 Ford truck, but the valve looks similar in basic design to what we have, and the principals are the same. Extra bonus, it includes info on how the valve comes apart, and what the internals do.

http://www.4wheeloffroad.com/techarticles/suspension/131_0507_disc_brake_install_conversion/index.html

basically it shows how the metering valve comes out, and what exactly should be removed from it in order to optimize a 4 wheel disc setup. When the damn snow goes away, I want to try this. It looks simple enough.

[87gtVIC]

So your interest is basically in this

The last step is to remove the residual pressure valve from the master cylinder. This valve holds a small amount of pressure in the line as needed by drum brakes. This pressure is detrimental to pad life with disc brakes and so must be defeated. Disconnect the rear brake line running from the brake port (fed by the smaller of the two reservoirs) and thread an extractor or No. 6 sheetmetal screw into the brass seat. Being careful not to deform the brass, pull it from the cavity to gain access to the valve. Remove the small rubber flapper valve and reinstall the brass seat. Tap the brass seat into the proper position and bleed the master cylinder before reinstalling. Finally, bleed the rest of the brake system by starting at the wheel farthest from the master cylinder (right rear) and working toward the closest (left front). Approximately 40 pumps of the brake pedal will bring the inboard (moveable) pad to within 1/32 inch of the rotor for proper clearance. Carefully drive the vehicle and check for correct brake function and a firm pedal.

And this

If you're adding an aftermarket adjustable proportioning valve along with rear disc brakes, the factory valve must be modified as outlined here. The factory proportioning valve (A) must be gutted by removing its internal spring. There is also a metering valve at the front (B) that balances disc/drum system actuation by holding off pressure to the front discs until the rear drums catch up. Remove the small washer (arrow) near the middle of the valve to disable it. From the factory, the bleeder rod (C) must be held out by a special clip when bleeding the system. This will no longer be necessary once the metering valve has been modified. Many people may want to ditch the entire valve, which is fine, but then the brake warning light switch (D) will no longer operate unless it is relocated. Note also how the combination valve serves as a handy junction block for the four brake lines. The pressure differential valve (E) senses any hydraulic pressure imbalances between the front and rear brakes and alerts the driver with the brake warning light. This valve is not modified, but be sure to mount adjustable proportioning valves downstream of this valve or your warning light will stay on permanently.

[gadget73]

I don't want to remove the factory proportioning just yet. I just want to remove the metering function and the residual valve. There might be something to gain by altering the proportioning but I'll take on the known issues before messing with the unknown. I would just love to have those proportioning specs off a later car. So far I've had no luck. If I really have to, I can go with an adjustable prop valve, but honestly I'd prefer known factory settings over a knob that can be arbitrarily twisted. I have no idea how to tune a specific value with those valves.

[Glen]

I will wait for more input.