I know that this post may not belong here but I know Ivan lurks around here so here goes.....Ivan you put rear discs on your truck right....If so what did you do about the master cylinder etc.... did you add an adjustable proportioning valve? I was just wondering because our trucks are similar and I just put discs in the rear of mine and now my pedal is a little soft and the rears lock up....any thoughts? thanks

 

Logic would say that that ought to solve things...

Course logic doesn't dicatate lifts, 40"+ tires, or stroker kits

 

He hasn't done it yet, but you absolutley have to add an adjustable proportioning valve. Summit and jegs has them cheap.

 

pro is right the propertioning valve for the drums is different they need more fluid to move the the required distance, and when you put the disks on not needing the fluid they will lockup before the fronts start to stop the vehicle changing your balance of braking.

 

I'm a slacker, what can I say? I had too many other projects going so the D70 is still sitting in my garage. The proportioning valve is about $40 and can go anywhere on the line to the rear brakes. I'm not planning to change the master cylinder other than upgrading to an F350 booster and MC for a smaller diameter. I'm thinking I'll keep the stock proportioning valve in place and just add the adjustable unit to the rear line right after it. The only thing I'm not certain about now is I have heard from several people that there is a valve (I think in the MC) that holds a slight bit of pressure to the rear drums and it will make rear discs drag a little. If this happens you can drill out the valve and it'll work fine. I had a thread in the brake forum where some guys offered up some great advice on how to do this: https://www.ford-trucks.com/forums/s...d.php?t=290767

 

I am doings this to my 82 flareside (9" though) and i am using the mc, porportioning valve, calipers, mounting brackets from a 78 lincoln mark 5. I also ordered and have a wilwood p (i'm to lazy to spell it out again) valve from summit for 36 bucks. If i were you i would get the p-valve from a late 70's lincoln or ford versallies to ge that fuild flow right.

If i were you i would get a p-valve and put it on the rear brakes to keep them from locking up. Oh and valve ivan is talking about is so the rear drums grab before the front brakes do because the shoes on drum brakes sit further away from the drum then the pads sit from the rotors.

 

ok so I decided on definetly getting the adjustable p-valve from wilwood. and see how that goes.... I am wondering about this built in valve that keeps pressure on the brakes, if I dont drill this out will I have brake failure or just premature brake wear or what? also will the adjustable p-valve help with my soft pedal? thanks again

 

The valve should firm up the pedal feel, as far as that valve i can't remember what the guys from jeff's bronco graveyard, i would go to their site and send them an e-mail like i did.

 

The adjustable valve will not solve the soft pedal, it will solve the rear brakes locking up. The soft pedal is due to simple hydraulic principals- the rear calipers have a larger surface area being pushed on (by the fluid) than your old drum wheel cylinders. This makes them multiply the pressure delivered moreso than the wheel cylinders did. but the tradeoff to this is it requires more fluid to apply against the larger area. The 4 wheel disks on my outlaw racer were just guessed at and they feel spongy but when you really put some effort into it they lock up pretty easily (no booster either) Ivan- when you are ready to do your rear disks heres a cheaper way than that kit you were talking about- 89 Dana 44TTB rotors, have your dana 70 hubs machined so they will seat on the backside ( or you could grind it- but it looks like a huge pain) I used the wheel studs from the 89 front hubs too. Then get some of those weld on caliper brackets that use GM calipers (not the metric ones) I got mine from Speedway motors in Lincoln Neb. I have used other ones in the past, and they always needed to be ground on in a spot or two to get calipers to fit, but the Speedway ones were the best fitting ones I have ever used- only grinding I did was to take paint off for welding. Also, there is a caliper available that has a larger piston than normal- I dont have a part # but it is some kind of heavy duty brake option( JL7 i thing he said, if it matters!)

 

It's called a residual valve.

 

The residual check valve should be removed that is usually located between the master cylinder and the brake lines going to the rear brakes. According to Dynatrak and several others I have spoken with, this vavle should be removed. I believe you should be able to remove it instead of drilling it. You may still need to change your master cylinder and or booster to the dual diaqhram unit off of a 250 or 350 to help with the spongy feel.

 

If you use this p-valve would it be unnecessary to use an adjustable p-valve, like the wilwood?

 

will the lincoln master cylinder firm up the pedal then? If I use this would I need to use external residual valves at all? Also will the lincoln master bolt up with no mods? The truck is a '79 f-250 with a dana 60 front for those who dont know.. thanks again

 

Hey Wyld
I did that conversion on my 9 inch, except I used 89 Bronco hubs for the 5 lug, along with the Chevy weld-on brackets and calipers. The problem I had is that the Chevy calipers were designed to work on non-vented (hence skinnier) rotors, and the Bronco rotors are vented, therefore thicker. Even with the caliper completely compressed, there was about 1/8" of pad too much to let the assembly over the rotor. What I did was just grind some material off 1 pad on each side until they fit. Did you run across this problem also?

 

momudder...i used front '77 chevy K20 rotors and calipers so they were matched....sorry dont really know what to tell you there.

On another board, I have seen some people use a '86 E350 van MC what do you guys think about that? Also would this bolt up directly? what about the lincoln?