disc brake conversion kits????????????? expert opinions?

Don,, On the firebird MC I had to shorten the rod because the MC detent was at the face of the bore, not inverted like the original, This is making me wonder if there is a difference in the needed stroke to accuate correctly, you guys have any thoughts on this?
WDA I havent had time to stay workin on the van steady wish I had more info to share at this point. But im attempting it with no residuals and just an adjustable proportioning valve on the rear.

The 79 firebird uses the same caliper piston sizes we are using. Most calipers in that wieght class are the same.
The fronts are the same size calipers as the 74 nova and the g10 vans and they all take the 728 series pads.

The rear calipers are the same piston size as the FWD cadilac and toronodo rear calipers everybody is putting on thier vans. they all take the 7070 series pads. The rear calipers I have are from an 88 camaro and I donot recomend them because they do have larger pistons and that makes for too much rear brakes.

All these vehicles use the 1" pistom master for manual brakes 2 and 4 wheel disc. and they all use the 1.125" piston master for power brakes again both 2 and 4 wheel disc brakes. I recomend the 1.125" master for bothe manual or power. The pedal is a little harder but it is also higher.

The 79 corvete master is the one with the short whole (usually used with power booster) Ane thw 1968 corvette had the master with the deep whole in the piston, which is safer I think. But like mine when I added a booster I had to add a filler plug to the piston.

M1D

"You need to be sure you have enough stroke to push the piston into the master cylinder,,,,,,"
This is what I was wondering about. Our brake pedal setups have a relatively short throw, I was curious as to how it compares to a pedal hanging off the dash. distance the pedal travels compared to the distance the push rod has to travel to accomplish the job. do our old One lung MCs have a different stroke requirement than the duals we are trying to use. I know bore size is a factor here and larger would move more fluid with less motion and it would be pretty difficult to change the geometry of the original set up. Just thinking a little tweak might make a difference in pedal hieght. Forgetting the obvious safety issues would the 1 lunger move enough fluid to operate a 4 wheel disc set up?

Still playing with it. Pedal heigth and travel not what I was hoping for?? Maybe the digz will pull a rabbit out of his hat??

OK now I need to know !M!,or anyone else who did rear disc my E-brake cables are 16 inches too short.. What did you use on yours or where can i find others. I have the Chevelle kit and the cables are great but way off???????????[b]

Heres what I did, because I had nothing to start with. Salvaged the clevis type ends. The cable on the right side was crowded so I moved the retaining bracket to the cross member, On a stock line set up there might be some stuff in the way ,I'm not sure.

I made exstensions out of 3/4" 10 guage strap.

Then bolted it to the cross bar with lock nuts. (the thin strap is temporary ,I ran out of stock).

Digz you are a regular Mageiver!

Dont wanna here ya yellin' all the way from AZ, but make sure ya leave enough slack in the parking brake cable to get the caliper off okay, I found that I barely had enough where I relocated the cable bracket. The calipers have to move towards the rear to come out of the brakets. Also the brake hose should be given plenty of loop to help with that also. Searching for the elusive lack of pedal I am double checking all bracket clearences and such to make sure I'm not trying to pump iron like a spring. The notches in the Caddy caliper pistons are giving me some grief, I didnt have it clocked quite right to start with, had to remove the E brake arm and reset all that into a start position. A big pair of channel locks did the job there, to clock and compress the piston. One side done toniight, the other tomorrow and I'll have the camera with me then.

Exciting good luck.

I changed mine up completely. I went to NAPA and bought cables by length. and ran them both to one side like later vehicles. I just cant accept that cable near the drive shaft u joint.





M1d

That looks way nicer M1, Have you got the part #s for those cables? Definately would like to go that route if I change up or do another .

my part numbers wont do anybody else any good. My callipers mount reversed so the cables are not thye lenght you need.


Front cable


You can buy them by measeurement from napa, the only thing is they need to know if they are rear or foward cables because they don't know what ends they come with. Its best to go to a bone yard with a measuring tape and look at examples there then get the year and model of whatever you are looking at and go buy them new for that application.

I had to modify the ones I bought by removing the drum brake return spring. Nothing about modifications are easy.
M1D

Im posting this for information , in case anybody else that is as unfamiliar with these types of brake as I am trys the kit. The Kit pistons came clocked out of position. you can see where the locking nub on the pad was riding.

I had to ratchet the piston out some to be able to rotate it with the pliers for some reason.

To retract the pistion I had to remove the arm assembly to clear the stop cast into the caliper and rotate and compress a couple times to get it back.


The kit comes with this anti rattle clip also that seats in a groove on the outside edge of the piston.

this is the nub on the pad aligned with the slot in the piston.

After remounting the caliper on the rotor I would recommend ratcheting the piston in before putting the cable and return spring back in place.

I then re-bled everything ,double checked and even added some clearance on the front caliper brackets because I noticed the extra humidity we have had here caused some rust around the ears where the caliper moves. All this gained nearly nothing on the pedal. But I did notice that my front left caliper is unloading itself quite abit for some reason, so next on the "to try list" is the residual valves, I played with the eccentric on the MC and found I could gain alot of pedal ,problem there was the brakes stayed on all the time, . That is a touchy adjustment, got that backed off so it would release the brakes and tightened it down, The plunger moves about an 1/8 of an inch before engaging the brakes, this is about 1/2" on the pedal movement. Anyway I do have some brake and will let it stay there and move on to the other stuff for now , Play with it more when work quiets down.

Hey did you get a kit for the front too? I dont seem to have a problem with the back calipers from the Ebay kit..Though I didnt look that close? I have about half a pedal , but it needs to be double pumped.
I like booster idea??

No kit for the front that I am aware of , Used the brackets and then went shopping for parts that would fit, Same rotors as the rear, 86 K5 calipers .
I'm sorta thinking a caliper with a smaller bore piston might make more sense if there is such a thing.
We only have 1" of stroke with the brake pedal geometry we are running. If ya do the math this can burn up nearly all the stroke getting the pads fully engaged to the rotors. I also gain pedal on the 2nd pump. We are not all running the same front calipers. Is there a big difference in the choices? Need some research there I guess. Does a booster increase the stroke? Out of my league on stuff that techy.

It appears to be the same with my all wheel disc set-up guys! I too seem to have just half a pedal?? I have yet to take it for a road test?
B.W.

The only thing a brake booster will do is make the pedal easier to push. Thats all! It would be more appropriate to call brake assist. But in terms of free play it can add another area of slack if not adjusted properly

M1D

If you go to the napa site and look up pistons for rebuil;ding calipers you will see the sizes. Just make sure you are comparing the same type caliper. I just checked 74 nova, 75 G10 van, 79 trans am with manual discs, and 78 K5 blazer. They all have the same size caliper piston. Gm made alot of stuff the same.
I showed earlier on this posting that I too have about a half pedaL. I dont think you will get better then that. But if you do get better on a second pump then you have something not right at the wheels.

Oh and by the way all the above mentioned vehicles use the 1" master for manual and the 1.125" for power brakes.
I think the problem feel is in the pedal geometry. I am ok with that because I have full brakes when the pedal is 3" from the floor and thats plenty.

I had made comment earlier on that cam bolt adjustment, you are adjusting two things at once. You can set the cam so it has just the right amount of free play but in two positions. One gives you a little better pedal then the other. You want to adjust the free play and end up with the bolt as down as possible, or furthest away from the fulcrum(piviot point) of the brake pedal. Theres something to do the math on. if you set the cam bolt closest to the piviot point you could loose up to 1/2" of pedal right there.

M1D

Let me try to understand this??? The calipers are a rare type that ties the e-brake cable to them. And if there is no e-brake hooked up you have to ratchet the caliper to absorb un-used space 1/4 inch? But if you have the e-brake cables attached.modified, the ratcheting is not needed? By doing this it makes the fluid travel much less distance and less pressure is needed?
Is it only these Cadillac calipers that have this issue? Digz and I both are having some problems with this, is anyone else??

I was taking a gamble by not installing the residual valves, I have not had time to get anywhere near the parts store to order them yet. The rear E brake being adjusted should just make sure you get as much fluid in the caliper starting out as possible and "maybe" prevent to much unloading, pressure should be okay that would be tuned in by the proportioning valve.
If air is out of the equation, the MC on a 1" bore moves .785 cubic inches of fluid. "IF" you have .020 inches of unloading in 4 2.5 inch calipers, that requires .392 cubic inches of fluid to overcome. approximatley 1/2 a pedal.
These are rough numbers BTW on piston sizes, but you can see what I am thinking. toss in rubber hoses, it doesnt leave much room for error.
If you have 1/2 a pedal on the first hit Id say you are home like M1 said.
Drum brakes are sort of self actuating so takes less fluid to make'em work, the discs takes all you can give them. I think we will be fine tuning this set up for sometime. An 1 1/8 bore MC would move more fluid and gain pedal but might need the power assist to be "comfortable". I know I am repeating alot of what M1 has said already, just thinkin' outloud sort of. My left front caliper unloading so much could be simple "path of less resistance" back to the MC or maybe the wheel bearing is a bit to loose, have to recheck that yet. LOL in other words ,I'm still working on it.

I used to have a Cadillac Seville with that style calipers. For the longest time I couldn't get the rear brakes to function. No amount of bleeding would make them work. After much studying and asking questions I found the answer. Those calipers self adjust when the parking brake is applied. Moving the lever back and forth should tighten them up. Sometimes the adjustment mechanism inside the piston gets seized. Fixing one-way clutch is easy. Pop out the piston and carefully pry out the star shaped retainer by working it out evenly with a small screwdriver. Pull the guts out and clean everything up. Lightly grease the mechanism. Make sure to thread the adjuster shaft all the way in before reassembly. I found that if I were to apply the parking brake once a week or so the rear brakes would work fine. A tip I got from the former owner was to only use organic pads on the rear to prevent brake groan as the car is coming to a stop. by Deiselvan vcvc

I have been told these are great??
http://www.speedwaymotors.com/Electric-Power-Master-Cylinder-with-Adjustable-Proportioning-Valve,9643.html

I think this is finally done. I have about 3/4 pedal good stopping not the Mercedes I hoped for. After blowing the first 2 masters (corvette and original type) With the pressure bleed-blaster.. We went with a Ford f250. The hot rod shop told me they love them if you(me) are too cheap to buy an electric master with booster. So far so good. It looks like everybody in town has added a brake line or valve in the front

Interesting,
What year or model or part number is that ford master. Do you know its principal demensions?

M1D