Thanks Yaga, do you really think that could be an issue, I wondered about this myself ( as far as small reservoir feeding the rear ) I really dont know, that IS the way I have it set-up now.

Maybe i should switch it but I also think to myself that the reservoir does not even show any signs of less fluid when the pedal is pressed so evidently there is enough fluid.

I dont know

 

Yes, I can plug the master with the two plugs provided in the kit for bleeding and the master cylinder plunger still travels all the way forward, here is how it looks,

1- I plug the master with the plastic plugs provided

2- fill with fluid

3- I push the plunger ( evidently too far according to Cordone ) and watch the air bubbles come up

4- I keep doing this until I see nothing but a steady stream of fluid coming up out of the holes on the bottom

I guess its starting to sound like something is not right ???

 

From Cordones website..........In the past, CARDONE supplied a bleeder kit that consisted of plugs with holes. Tubes pressed on to the holes in order to bench bleed the master cylinder. Although this kit was successful when used properly, it was not the best process. One of our goals in Technical Services is to improve every process.

 

Physics suggestsonce the system if full of fluid it will act on the brakes reguardless. Most stopping power comes from the front brakes anyway.

As yaga said if the cyl is plugged and bled and you still gwt full stroke the seal on the piston is probably ruptured or bad.

 

BTW that was a brand new nicely painted master cylinder this A.M

 

Well that stinks, I guess thats it than until the other one arrives, no sense on wasting another gallon of brake fluid trying to bleed something that is bad, thanks guys

 

It would be nice if someone could verify how to identify what a step bore master cylinder is, sounds to me like there are two different size pistons within that master and so one being larger than the other would cause the casting of the case of master to have a step appearance.

EDIT: Ok I got it, no I do not have a step bore M.C. might sound like something I should have though

 

Step bore master cylinders are used on things like fork lifts where you need to displace a lot of volume to take up slack then still have a pedal that doesn't take both feet.

First question, what is the original master cylinder bore for this truck?

Second question, do you have residual pressure valves installed? Drum brakes use a residual pressure valve to keep the wheel cylinder pistons against the shoes.

Third question, how are the shoes adjusted for proper clearance on the drums?

Fourth question, are you still using front drums or did you convert to discs?

I know on my buddies 1955 Dodge pickup street rod, we had a bit of a problem getting his brakes right, partially his own fault.

 

All great questions, the original master cylinder bore was 1.5......the closest to that I was able to find and bolt onto my new dual chamber F-350 above 8500 GRW ( I think its GRW or GRV ) was 1.25 bore size.

The original wheel cylinder bore sizes were

Rear 1 5/8......These wheel cylinders are made from unobtanium so the closest that could be found and still fit within the cages they fit into was an F-8 wheel cylinder which is 1 3/4 = 1/8 larger

I did find out though that F-7 and F-8 used the same 1.5 bore master cylinder.

Front wheel cylinders on F-7 and F-8 were same size of 1 1/4......I have replaced all 6 wheel cylinders, 4 in the rear and two in the front.

Yes residual valve will be the red thing you will see in the picture I posted above.....Master cylinder outlet ports or rather the size of fluid outlet ports are 3/16, I was told to mount 10 lb residual valves as close to master as possible, I came out of master with 3/16 line into residual valves plumbed for 3/16 line....I then upped the line to 1/4 the rest of the travel throughout the truck.

Yes I do believe the shoes are adjusted properly although I need to re-visit proper adjustment of the front shoes, its easy enough to see how the cams move out the tops of the shoes but I need to see how the lower half is adjusted.....at this point all 6 wheels have a slight drag on the drums when turned.

Drum brakes ( original ) all the way around

 

Ok, first item, your original master cylinder was almost 1 1/2 times larger in area. This means that in order to displace as much fluid, you have to move the piston 1 1/2 times further. Second, your rear cylinders are 1.16 times larger area than the originals, this means 1.16 times as much fluid needed per unit of travel. You are probably with everything just barely free at the absolute limit of volume per stroke. I thought I could find my information I dug up when I converted my truck to a later rear and brake system. The 92 up F-350 used the same cylinder diameter as the 86.

 

I know that its a bit stretch, but the first go around I was using a 1.0 master bore size and single chamber f-250 power booster and I did not have a problem getting the truck to stop, my problem was having to pump the brakes to get any pressure before stopping which I am assuming is going to be taken care of with the residual valves and a better bleed. ( I hope )

I did not have these ( residual valves ) in place first go around and on top of that apparently the wheel cylinders ( two of them in the rear ) were still ( as I figured ) full of air since the bleeder screws would have been below the fluid line as franklin pointed out due to myself and the last owner just plain not knowing any better.

The way I am looking at it over the original is that I am losing 1/4 of an inch over the master cylinder bore size over the original design ( nothing more ) but I am gaining the dual chamber master now as apposed to the original single chamber feeds all set-up and the booster set-up I have now will give me a greater assist over the inefficient original.

 

Reading all the above posts, I believe his problem is air in the master. I have done this many times, and what you do is use the plastic plugs and plug the outlets of the master(tighten them as much as you dare without stripping them out) put it in a vise, take a big screwdriver or something that will fit in the hole, make sure the master has fluid in it, and start pumping(the only cars I have messed with that had step bore masters where GM models).

Pump, pump, pump with the screwdriver. You will see little bubbles come up out of the little holes each time you pump it. The travel should get shorter and shorter as you pump. Do not get frustrated, I have almost several times, because I have pumped some of these things over 30 times to get all the air out. When you get ALL the air out, the input to the master will NOT BUDGE AT ALL. It takes a long time to get it to this point, but it will get there.

P.S. You rear wheel cylinder are plumbed ok. The bleeder is above the line fitting on the wheel cylinder.

 

Your bore size will affect your pedal travel, but you will still have brakes. The point at which they apply will be the only difference in the different bore sizes, and the amount of foot pressure it takes to apply them. That will be something you can decide on later after you get them initially working.

 

I think you misunderstood my post, the rear wheel cylinders were NOT OK until I went out there and made them Ok as per your post.

Have you found this too be true ............Using a blunt tool or dowel (brake pedal if mounted in vehicle), SLOWLY press in and release the master cylinder piston using short strokes of 3/4” to 1”. NEVER STROKE PISTON MORE THAN 1”. Repeat this step until resistance to piston movement is firm and less than 1/8”.


NEVER STROKE PISTON MORE THAN 1

NEVER STROKE PISTON MORE THAN 1

NEVER STROKE PISTON MORE THAN 1

 

Exactly what I am hoping to accomplish