front disc brake conversion questions

well, being a old die hard i never thought i'd ask this. has anybody had any experience converting to front discs on an early b-body without a power assist? i'm at my wits end on my 65 coronet. everything in the brake system is new. it has praise dyno ceramic-metallic shoes and 11" drums. i have a nice firm pedal but i almost need to use both feet to stop the thing! the pedal effort it takes to stop is ridiculous. my 69 r/t has virtually the same system, except for asbestos shoes, and stops reasonably well. i've been reluctant to convert because i've had disc brake cars that wouldn't stop. any ideas?

I think those ceramic shoes have to be hot to start working right. You might try larger bore wheel cylinders or a smaller bore master to get more squeeze on the shoes. A brake booster would help.

The '73-6 a-body disc spindle fit the early b-bodies too. My brother used them on his '64 Dodge 440 and even used the a-body hoses.btw he used a junkyard aluminum dakota power brake master cyl but installed it as a manual master cylinder with no booster on his car. Stops good with no issues.

Maybe you could put some regular disc brake pads on and see if the braking action improves (after they "bed in"). Otherwise, I'd say it's the master cylinder bore diameter. Don't quote me on this, but I think a bigger bore makes for a harder pedal, and smaller bore makes for easier pedal effort. I used regular NAPA pads and a manual master cylinder from a '70 Belvedere application (no idea what the bore diameter is) and my '64 stops just fine.

I've put a bunch of different manual brake setups on my '65 Coronet. They've all worked great with very good pedal feel. The easiest solution is to take the whole setup from a 1973 to 1976 A body car and just bolt it on there.

I think you have a wrong size mastercylinder. I run 13,15" discs with big red calipers, with Hawk blue - will outbrake almost anything!

It sounds very similar to what happened to me. I had two new front drums and brake shoes put on my car ('67 Barracuda) back in December. The brakes would haul the car down from speed, but it just did not want to stop at all. I had to use two feet and it still would just barely stop. My front-end guy had put Raybestos bonded shoes on it. He didn't do anything other than change over to Bendix riveted shoes and everything works fine now. For some reason, the Raybestos shoes just didn't react well with the drums (btw, I got the drums from the Paddock, and I think they also were Raybestos).

Like Andy said,there are lotsa' option's out there,I used '81 cordoba units on my 63 sport Fury,and on several later 68/69 RR's,but I'd turf the oem style pre '66 single pot m/cyl. my '62-64 Fury's have alway's been fine with 11" drums,I just grabbed a set of 11" drums from a '68 charger,that is in my shop for paint,my buddy doesn't want them,I'd rather bolt them on my '62 fury than the disc's, I bought a supply of NOS m/cyl's for a 66-67 belvedere years ago, and switched up to that dual reservoir,manual drum style m/cyl.with no booster,I think you should try a different set of shoes first,and let us know which master cyl. you are using,maybe you have a line or distribution valve blockage,bad wheel cyl. ??, could be something minor,the 11" should work with a lot less effort,,If you think you need it,I do have a '70 B body booster and manual master cyl. for drum brakes,kickin' around here someplace.

Find out if the drumshoes make contact over their entire surface-area. If not, they probably don't follow the same arc and diameter of the drum and need to be 'curved' to match the drums better.
A smaller MC could help aswell probably.

I converted my 64 Fury over using the 73-76 A body set-up and didn't use a power booster. The setup works great.

Dusta, sounds like you're happy with your setup. Maybe start a post sometimes showing your setup and the experience you're having road racing. We don't get many road racers on this board.

i've had 2 master cylinders on the car. the first was a 67-69 replacement dual with a 1" bore. i have the fine lines kit that splits the front from the back, new stainless lines, hoses, wheel cylinders, hardware, etc. a couple of weeks ago i put one of the alum master cylinders on (1 1/16" bore) i purchased from magnum hp (fits good). there wasn't any difference in pedal effort between the two. the ceremaic-metallic shoes don't fade with repeated 60mph stops but the pedal effort is too much. i've got a ton of $$$$ in this and hate to give up on it. i've thought about a power booster but would need the toggle linkage and plate to make it work. there aren't any old mopars in salvage yards around here to get parts.

i've thought about an ssbc or wilwood front conversion. don't know if it will work without a bunch of extra parts. i've heard that disc's without power assist have a lot of pedal effort also, don't know if thats true or not.

Everybody is telling you what to do and they don't have all the facts, I guess everybody here only reads what they want to and not whats posted by the topic starter! I can't give you a answer because of the following.
Gator- you say everything is new, but new with what? Nowhere do you state what componets you replaced them with. My question to you is " Are you running a single or dual Reseviour{sp?}? That can make all the difference in the world with whats going on with your brakes.
This post should be thrown out and starter over with you stateing ALLL the fact with your brake system and I'm sure the answers will be totally different.

Gator, I don't see anything about a proportioning valve. You need one.
My '65 has '74 A-body setup, '67 replacement dual master cylinder, Finelines proportioning valve, and pedal feels same as with old single pot m.c.
Hope this helps you.

If you put the 11.75 B body rotors on there the pedal effort will be just fine with your aluminum master cylinder. You don't need any aftermarket stuff, just the late A body (or late B body) knuckles and the big 11.75 rotors.

I covered this entire swap on my website in the article section.

On a side note, I found a place that sells a power booster that works with the manual pedal. It has been shipped and I should have it by next week. Mine is a 65 coronet. I will post how it goes.

both master cylinders that i have used are dual resevoir. the parts replaced are new wheel cylinders for 11" drums, new hoses, new brake lines, new springs, new Praise Dyno ceramic-metallic shoes and spring hardware. early b-bodies never had porportioning valves. the single resevoir master cylinder fed into a block that tee'ed out to the front and rear lines. i have never used that system. the Fine Lines conversion doesn't use any porportioning valve, it just simply splits the front and back. i thought my statement of parts in use was covered, maybe i wasn't clear, .

I wonder if the shoe material simply requires more pedal effort, since you mentioned that your other car with standard type shoes seems to be fine. Another option would be to move the pushrod mount on the pedal to increase the leverage.

greg, you may be right about the material. i have a set of new asbestos shoes (like whats on my 69 r/t) i probably ought to try before doing anything else.

Try the asbestos linings, Id bet the ceramic linings arent getting hot enough to work right.

64Belvedere and Dusta hit the nail on the head! You have to big of a master cylinder. Small bore = more pressure. FORMULA FOR OUT PUT PRESS OF MASTER CYLINDER
You want a 1" or 15/16" master cylinder, since the wheel cylinder in the back are 15/16 you can not go smaller thant 15/16 bore master cylinder, or you will run out of brake fluid.

There are boosters made for the Mopar they cost under $250 for booster, bracket, and m/c.

If you have a vacuum problem and still can not get you car to stop. Do the following:
1. switch to a 4 piston fixed caliper up front;
2. replace the 15/16" wheel cylinder in the back with 7/8 or go to a 4 piston 1.38" piston caliper set up.
3. use a 7/8" master cylinder this will give you an output pressue of almost 1,000 psi with a 6:1 pedal ratio and 100 pounds of applied pressure with your foot.

Normally takes 1,000 to 1,200 psi to lock up the front brakes.

BTW: Here's a picture of a "Z" rod bracket for the Mopar Booster. But dont waste money on a booster without first checking your vacuum.

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64Belvedere and Dusta hit the nail on the head! You have to big of a master cylinder. Small bore = more pressure. You want a 1" or 15/16" master cylinder,

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If you read above, you'd see he had the same problem with a 1" piston bore. My bet is still on the lining material.