Brake Proportioning Block

Ron816

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My friend has a 67 Belvedere, had manual 4 wheel drum brakes, installed a power brake booster as well as front disk brake conversion. The pedal has about a 4-5 inch drop before the brakes engage, when the do engage they feel mushy, all 4 wheels and master have been bled, my question is there a different proportioning block for manual to disk?
 

4mulas

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There is yes. You should have a disc brake proportioning valve for that set up. One from a 73 and up body with disc brakes should work. Doctor Diff sells them for around 80 bucks.

However, your problem sound a little deeper than the wrong proportioning valve.

I think the manual vs power brake pushrods may also be different in length from each other. Did you change that too?
 

Ron816

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There is yes. You should have a disc brake proportioning valve for that set up. One from a 73 and up body with disc brakes should work. Doctor Diff sells them for around 80 bucks.

However, your problem sound a little deeper than the wrong proportioning valve.

I think the manual vs power brake pushrods may also be different in length from each other. Did you change that too?
Yes push rod has been changed and has been measured for correct length
 

Fran Blacker

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Did he put a disc brake MC and adjust rod in booster so there only .020 before rod pushes MC piston? Agree with 4mulas.
 

Ron H

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Tricky areas when going to power is the proper adjustment of the booster push rod into the MC, there's a tolerance for this, mine (earlier B) was around 15 thou. The other thing is the pedal ratio that changes btw manual & power...you may have a 2nd hole in the pedal arm for this.
 

70bigblockdodge

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My brother-in-law went on and on about power brake conversion in his '71 340 'Cuda. I said you have 11"×3 & 2.5 for a 3700# car with him in it. How does it not stop? Turns out 2 wheel cylinders were frozen. I made the brakes work properly, he has never brought up the conversion again.
I can see if you want to drive alot or aggressivly and disc brakes. Power brakes are for my wife.
 

Ron H

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Couple added things you may know; but tossing them out as I went through a hassle with my conversion (aside from the post here getting the proper valve). As I received the wrong kit for my car making it work should have been a bell-crank set up (older setup N/A with yours) is assuring the booster is pushing the MC plunger far enough into it…no short stroke. I had this problem; but again due to wrong kit (ended up staying with the manual ratio longer story). Also ensure there is a bit of free-play when pedal is in home position, not being stopped by the brake light switch. This has to do with not pre-activating the booster giving other ills. When time comes for this, recheck the rear brake adjustment after installing the valve as the next thing will be getting this adjustment correct. In my case the drums were well-worn, about maxed out so installed new ones.
 

Gus chiggins

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Why does everyone want power brakes?
Just wondering, during a panic stop do power brakes perform better, or do manual brakes? It's like people saying .380 is ineffective, but a walther PK with critical defense ammo...good stuff.
 
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