hard brake pedal after disk drum conversion

Hello, I have a problem and have gotten some ideas on this problem but nothing seems to work for me. I saw a post on here from last year but did not get the full information about hard brake pedal and hard to stop 57 Buick converted to disk/drum setup with power. I have been working on my father's 57 and have this issue and can't seem to figure out what I need to do. Car was originally power brakes car from factory and continues to use the original brake pedal assembly. In the posts from two member last years they mention that a change is needed to acquire the correct pedal ratio so that it feels less hard. Does anyone have any pictures of a brake brake pedal assembly that has been modified or change and what did they use or what was done to correct this problem. I appreciate all the help any one can give me to fix this and get my father back on the road with his pride and joy (in the automotive area that is).

 

Sounds like your booster is pooched.

 

I don't know that it has a lot to do with the length of the brake pedal bracket.

Are you using the original type master cylinder? Do the brakes seem to stay on? I just learned here that disc and drum brakes have different residual valve requirements. If I remember correctly...2lbs for disc and 10lbs for drums? And the valve is located in the MS. So I think a drum brake MS would tend to hold the disc brakes on.

I might be wrong...as usual...lol.

 

http://www.piratejack.net/index.php?option=com_content&view=article&id=11:typical-brake-system-configurations&catid=12:tech-support&Itemid=18 Brake set ups Basic info

 

JOYFLEA may have answered your question in your introduction.

 

These may help:

http://www.classicperform.com/TechBook/BrakeTroubleshoot.htm#pedal

http://www.classicperform.com/TechBo...ot.htm#pushrod

Links are from ACARDON, a regular on ChevyTalk.com and Trifive.com

paul

 

Can the combination valve be the problem, it is installed at an angle it is not leveled to the master cylinder in a horizontal way. It is actually angled down at about a 45 degree angle. Just a question trying and asking everything. I am using a 1962 cadillac booster, any suggestions on whether this is the right one to used or not.

 

this may or may not apply to your situation, but...

if you have a proportioning valve installed, and if the brakes were not bled in the proper sequence, the valve may malfunction and create a hard pedal.

 

Sounds like a dead power booster or the one way check valve is shot or plugged.It's the plastic piece that the vacuum hose connects to. To check for external leaks. Start the engine , use propane or mapp gas torch. Don't use acteleyne!!!!

 

I was always told to bleed the cylinders or calipers furthest away from MC and then the closest. Is this correct or is there another form and I may have made a mistake

 

Disc brakes need a higher line pressure than drums. What are you using for a master cylinder? Also you must install a proportioning valve for disc/drum systems when you do a drum/drum to disc/drum conversion. You need what's called a combination valve.

Good info - http://www.mpbrakes.com/technical-support/reference-disc-brakes.cfm

Test the booster by pumping the brake pedal 10 times with the engine off. Press the pedal till it stops and hold it there. Start the engine and you should feel the pedal drop a bit. If you don't feel that there is a problem with vacuum to the booster or the booster itself is bad.

Pedal ratio is easy to fix/check. Google "brake pedal ratio".

Go here and do some reading it will answer a lot of questions -

http://www.mpbrakes.com/technical-support/reference.cfm

 

OK, problem solve the booster that we were using was a single, we replaced it with double and a MC from 76 Buick Riviera which is Disk/Drum. Works like magic stops great, even though it still has some residual air in the line that we are currently bleeding out. Yes just as I'm writing we are working on it, the car was promised for a wedding tomorrow. Gave the bad news to the bride yesterday, looks like it will be a surprise when she sees it picking her up tomorrow.

Thanks to all great information on the booster, you were right on the money. sometime is the simplest of things.

 

Yaaaay!

 

Awesome! Had the same problem on a 65 impala conversion. Glad it worked out


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Good deal! Thanks for the update.

 

I glad it all worked out .......