Manual Brake Pedal Feel - front disc/rear drum

[msbaugh]

I recently switched my small manual trans brake pedal for the larger automatic one since there was a conversion done on my car before I bought it. 

I put a right-stuff front disc brake kit on my car and decided to stay with manual brakes and leave the drums on the rear.  I have always had a decently stopping car, (decent) but the pedal has quite a bit of slop feel to it and just doesn't seem right.  The master was completely bled and there is no air in the system, the pedal does not go to the floor.

Its like it gives no pressure the first 1/3 of the way down and then it starts to firm up once I get there.  I noticed when I swapped pedals that the pushrod just kind of fell out of the master cylinder from inside the car.  Does someone have a diagram on how this is held in?  All it has is a little rubber ring around the master end of the rod where it goes in. 

Its like there's slop in the pedal and no resistance at first when the master is pressed in.  I tried adjusting the pedal both ways up and down and neither seems to help, when I finally get it where I like it, the pedal wont return far enough up to release the brake light switch and turn the brake lights off

[Bullitt-]

The brake light switch is adjustable.... a little anyway 

[msbaugh]

Idk the brakes just don't feel right to me... It has what I think from measuring is a 1.13" bore it's a cast iron 4 bolt master.  Also the two lines from the master go to a junction block with the low brake light wire on it.

I think this is a stock 4 drum junction block. Would I have bad pedal feel from having lines run to the rear straight from there? Because I didn't put any rear adjustable proportioning valve on the back.... The rear brakes don't lock up either

[Bullitt-]

If it's the OE style master cylinder for drum brakes you have a problem in that there is a residual valve holding pressure on the front brakes that should not be there.
I would think an adjustable proportioning valve would be of benefit.. 
A smaller bore master cylinder would help with pedal effort... some good info here http://www.cuda-challenger.com/cc/index.php?topic=66387.msg691106#msg691106

[Bullitt-]

info on master cylinder size

http://www.mbmbrakeboosters.com/index.php?option=com_content&view=article&id=7:master-cylinder-faq&catid=2:brake-boosters&Itemid=10

[Bullitt-]

this may help... has a calculator
http://www.markwilliams.com/braketech.aspx#calc

[msbaugh]

Sweet, I'll do some reading.  Im pretty sure it is a front disc/rear drum master because the front brake reservoir (rearward reservoir) is much larger

[msbaugh]

This is the metering block I have.  Can someone who might recognize it tell me what application it is for? 




I think I'll also replace this rusty looking master cylinder too.  It might be the source of my issues anyway.  THe aluminum one with the adapter bracket from Dr. Diff looks like a good one.

[msbaugh]

Bullit just read through the thread you posted, looks like what I have is not a metering block or a proportioning valve, it's simply brake warning switch, which could be part of my problem since I now have discs on the front

[Bullitt-]

Sounds like your on the right track... Punch up Brad about what size Master Cylinder he went with.. I see Shandango used a 7/8" bore.
Smaller bore will have more travel but take less effort than a large bore such as you have now...   

[Cruzin]

Is it possible that the replacement brake pedal you installed ("larger automatic one") is out of a power brake car?   This is important because the mechanical ratio are different between the two pedals (i.e. manual and power) sets.  This may also explain the issue with the pressure / feel you are experiencing and lastly, the brake rod falling out.

 
 

[msbaugh]

Is it possible that the replacement brake pedal you installed ("larger automatic one") is out of a power brake car?   This is important because the mechanical ratio are different between the two pedals (i.e. manual and power) sets.  This may also explain the issue with the pressure / feel you are experiencing and lastly, the brake rod falling out.

 

That's an interesting theory, but the rod is adjustable, so it shouldn't matter.  The brake pedal feel was like this with the manual pedal and is still the same after the swap