proportioning valve or not???

[m_m70]

planning on converting to disc on saterday.<br>I got all the parts including the proportioning valve and fittings. I really don't have the time to jerk out the h-block and make all new hard lines. have any of you gone with just the h-block??<br>Also I was told I have to take out some valve in the rear of the master cylinder. should I just get a new master cylinder? if so, would a stock bronco cylinder work from 76/77. I have a '70 this is going into.<br>Thanks,<br>Mike

 

[howiebilt]

are you converting the front or the rear or both ?

 

[mlogan24]

I previously was of the school of thought that the proportioning valve wasn't really neccesary and that they were troublesome, so i ran the h-block with my front disk (and 76 F250 MC). It worked, but now that I have the proportioning valve-much better! A good source for new valves is MP Brakes, plus they have good FAQ's on how a braking system works.

 

[lars]

I would't use the Ford proportioning valve, especially if you plan to add rear discs. Leave the brass h-block on the frame- it's a convenient way to join the brake lines and secure them to the frame. Get an adjustable proportioning valve and install it in the line for the rear brakes between the master cylinder and the h-block. In case you didn't know already, the rear reservoir on your master cylinder is for your front brakes. No reason to replace the master cylinder unless you are doing the Chevy conversion, you have a power booster and you decide the pedal is too mushy. Then you might want a master cylinder with a bigger piston. Sounds like you have manual brakes, stick with the one you have. BTW all early Broncos had master cylinders with 1" pistons, even the disc brake models.<br><br>The valve in the master cylinder port is a residual pressure valve. Only needed for drum brakes. It maintains pressure in the brake line when you let off the brakes so that the brake shoes don't retract too far from the drum. Otherwise (at least theoretically) you'd have to pump the brakes whenever you used them to get enough pedal. With disc brakes you don't need the RPV because the caliper doesn't retract. Leave it in and the brakes drag. But... many aftermarket master cylinders don't have them, for some reason. If it's in there, you can remove it using a long no. 8 sheet metal screw. Drive the screw into the brass bushing at the bottom of the port, then yank the bushing out. The RPV (if it's there) is just a ball and spring. Pull the pieces out, replace the bushing, done.

 

[Benzo]

I installed the adjustable Wilwood P-Valve. I ordered mine from Summit Racing. Part number WIL-260-2220 $39.99 plus $7.95 handling fee. You want full pressure for the front brakes, install it on the rear brake line inbetween the master cylinder and the h-block. It works great, it's easy to install and eay to adjust.

 

[m_m70]

I am just converting the front to disc.<br>If I install the proportioning valve could I do it before the h-block and leave the h-block in?? In the kit I bought (from WH) it says to remove the risidual valve in the back of the master cylinder. No big deal, I was just wondering if it would be just as easy to put a new master cylinder in and if '76/77 would be the right one with out having to remove anything from it.<br>this is all going to be done in one day so any advice is greatly appreciated. (may be a long day!!!!)<br>Thanks,<br>Mike

 

[lars]

[quote author=m_m70 link=board=5;threadid=12263;start=0#91002 date=1039751021]<br>I am just converting the front to disc.<br>If I install the proportioning valve could I do it before the h-block and leave the h-block in?? In the kit I bought (from WH) it says to remove the risidual valve in the back of the master cylinder. No big deal, I was just wondering if it would be just as easy to put a new master cylinder in and if '76/77 would be the right one with out having to remove anything from it.<br>this is all going to be done in one day so any advice is greatly appreciated. (may be a long day!!!!)<br>Thanks,<br>Mike<br>[/quote]<br><br>You didn't say what kind of proportioning valve you have. If it's the OEM Ford unit (long cast iron thing with lumps and fittings all over it, costs about $100 new) the only thing you should do with it is to return it, so you can buy an adjustable one like WrenchMonkey described.<br><br>If you have an adjustable one (small rectangular aluminum block with an adjustment knob on it) then yes, install it in the line for the rear brakes between the h-block and the master cylinder.<br><br>Sounds like you'd rather replace the master cylinder than pull the RPV. You can use a 76/77 master cylinder, but if you have manual brakes, be advised that the brake lines come out of the 76/77 master cylinder on the passenger side, instead of on the drivers side. You'll have to get new brake lines between h-block and master cylinder, and clearance between brake lines and throttle linkage might be a little cozy. Also, the master cylinder won't come with a brake pushrod. You'll have to figure a way to get the old one out of your current master cylinder.<br><br>As for doing it in one day, I'd say go for it. As long as everything comes apart ok and you have all the parts, you should be able to do it.

 

[74bronc]

[quote author=mlogan24 link=board=5;threadid=12263;start=0#90939 date=1039738140]<br>I previously was of the school of thought that the proportioning valve wasn't really neccesary and that they were troublesome, so i ran the h-block with my front disk (and 76 F250 MC). It worked, but now that I have the proportioning valve-much better! A good source for new valves is MP Brakes, plus they have good FAQ's on how a braking system works.<br>[/quote]<br><br>Can you describe "much better"? The reason I ask is because I did the Chevy disc swap in October using a 76 3/4 ton pickup master cylinder with no proportioning valve and my bronco stops great. No front end dive and the pedal is solid and high up on the stroke. In fact, the rest of the brake system is stock, with the H-block. I am just wondering if the bronco will stop any better if I install an adjustable pro-valve.

 

[cobranco]

I have four disc brakes, using the F250 master cylinder and 4 Chev. calipers, and no prop valve. Works great on mine. If you are running the drum rears I would try it without the prop valve first and see how it works. You can always buy the adjustable prop valve later if needed. Just install the valve in the rear brake line.

 

[chuck]

Only use the P-valve as a last resort. Put the system togather without any type of P-valve. If you have<br>premature rear lock up you have a few choices. larger front calipers, an LBS valve, smaller rear<br> cylinders, an adjustable P-valve and a stock type P-valve. Order of preference as above.

 

[eastcoasthop]

I've got a stock 76 and my rears lockup soooo damn easy its scary. Is it correct that if the rear brakes were to fail from pressure loss that with the stock setup the front brakes also would not work? I believe the factory valve requires pressure in the rear brakes to allow the valve to open to send fluid to the front. Therefore the wilwood valve should be installed downstream of the stock valve????? anyone??

 

[lars]

[quote author=eastcoasthop link=board=5;threadid=12263;start=0#91197 date=1039817013]<br>I've got a stock 76 and my rears lockup soooo damn easy its scary. Is it correct that if the rear brakes were to fail from pressure loss that with the stock setup the front brakes also would not work? I believe the factory valve requires pressure in the rear brakes to allow the valve to open to send fluid to the front. Therefore the wilwood valve should be installed downstream of the stock valve????? anyone??<br>[/quote]<br><br>Not so. The Ford valve is actually more accurately called a combination valve. It has the proportioning valve function for the rear circuit, the differential valve the turns on the idiot light if you lose pressure in either circuit, and a metering valve for the front circuit that slows the application of the front discs so the rears can catch up. Because the proportioning valve isn't adjustable, it can't compensate for variations in weight on the rear wheels or variations in brake shoe/pad compounds. With 4 wheel discs the metering valve is actually a detriment. If you lose pressure in the rear all that happens is the differential valve shuttles toward the less pressurized circuit (the rear) which closes the switch and (assuming it still works) turns on the red "BRAKE" light by your ignition switch.<br><br>Some people don't seem to like the older style h-blocks, but I do, simply because they give a sturdy way to support the brake lines and make the connections to front and rear. My recommendation would be to lose the proportioning valve you have, and replace it with a Wilwood adjustable model or possibly the LBS valve that BC Broncos sells. I haven't used one but they sound interesting. I agree in principle with Chuck's assertion that the best approach is to change caliper or wheel cylinder size, but that's not always practical.