Brakes bled and pedal goes to the floor but I do stop... sort of.

[chuzie]

bound4dixie, not sure that is a question for matt.

bucket, no.

On my way to pick up a different MC I ordered yesterday so more to come.

[broncomatt]

I dont belive the master is shot, I belive its incorrect for the size of the wheel clys, plus I dont think it has residual press valves built in. A guage would be great to have, but they often have to be plumed in permanetly. I have one in my front system to show how much press I put before I lock the the lever loc. Not cheap either.
It seems to be a volume of fluid issue. At the bottom of the stroke of the master there is not enough fluid press against the wheel cyls and calipers to properly stop the truck.
The bore seems right, but not enough stroke.
Broncomatt

[chuzie]

Ok here is the deal with the new MC and the Duff's MC.

Duffs
-------
Bore: 1.090 (slightly less than 1-1/8
Stroke: 1.650
Cylinder Depth: 8.03
Piston Diameter: 0.92

'69 El Dorado (4120)
-------
Bore: 1.131 (slightly more than 1-1/8
Stroke: 1.559
Cylinder Depth: 8.015
Piston Diameter: 1.120

The difference in bore sizes are significant enough to prevent swapping pistons between MCs. Duff's advertises a 1-1/8" bore and the parts store states this new MC is 1-1/8 too but someone or something is wrong here.

Also, the size of the new MC, in terms of capacity, seems larger than the Duff's MC.

The stock bronco rear cylinders are 15/16 and the el dorado rear cylinders are 1". Also the rear drum inside diameters are the same between the two vehicles.
The bronco OD of the front rotor is 298mm and the el dorado OD is 280mm.

Do you think with the larger bore and shorter stroke I can use this new MC or just bite the bullet and get a new one from Duff's?



Here are some pics....
Duff's MC on left
Duff's piston on top

[blazinchuck]

just get this and move on....this is what i bought. tha heck with them and their special MC

http://cgi.ebay.com/ebaymotors/1966-1977...ccessories

[chuzie]

R u going to pay for it? I am BROKE!!!

[blazinchuck]

R u going to pay for it? I am BROKE!!!

i wish i could, id do it for ya:xyxthumbs:

[bound4dixie]

I dont belive the master is shot, I belive its incorrect for the size of the wheel clys, plus I dont think it has residual press valves built in. A guage would be great to have, but they often have to be plumed in permanetly. I have one in my front system to show how much press I put before I lock the the lever loc. Not cheap either.
It seems to be a volume of fluid issue. At the bottom of the stroke of the master there is not enough fluid press against the wheel cyls and calipers to properly stop the truck.
The bore seems right, but not enough stroke.
Broncomatt

Yeah, like I said before, just trying to keep the discussion going so that chuzie can have some brakes before URE :xyxthumbs: I'm in no way saying that I'm an expert in any way :bdent:

So, if we believe that the volume of fluid is an issue, then you have to (A) increase the stroke or (B) use a bigger bore (I realize this will change the mechanical advantage too). Both of these will essentially increase the total displaced volume of fluid.

Since the rear shoes pull further away from the drums than do the pads from the rotor, would installing a residual valve on the rear drums not also reduce the amount of fluid required since you will have some fluid already in the rear wheel cylinders from a previous pedal press?

Chuzie, have you used a residual pressure valve at all yet or have you always ran without one?

[chuzie]

Never ran a residual pressure valve to my knowledge. I think that having one installed will make a difference in the future but now, since my rears are adjusted all the way out and the push rod is so far out the brakes are practically already applied before I hit the pedal there is very little, if any, surface clearance. Now, once the pads and shoes wear and I have no residual valve I will either have to readjust everything to prevent what you are talking about or find a suitable pressure valve.

[broncomatt]

That master will work, the larger bore and shorter stroke will make things apply faster, with a harder pedal. Be sure to properly bleed the brakes, and bench bleed the master to start. Then I use a peice of clear hose into an old brake bottle. Start at the right rear, then left rear up to the right front then leflt front. Put the hose on the bleeder, crack it alittle, gently pump the pedel several times slowley untill you see clear (new fluid). Double check the rear brake adjustment. You should be good to go.
Let me know how it turns out.
Broncomatt

[chuzie]

Ya right Matt, you make it sound so easy; I love you optimism though. Keep your fingers crossed.