so im swaping out my old drums for power disk. i was wondering would there be a problem if i changed the master cyl. to a bigger newer one and put in a brake booster but kept the original proportioning valve. or does the pro. valve need to be changed also?

 

Drum systems don't have a proportioning valve, so you will need to add that if you put disks on front. You will also need to add a dual bowl MC.

 

most power conversion kits come with the dualmaster cylinder and proportioning valve

 

i did put a dual MC. if drums didnt come with a proportioning valve what is the little valve/box thing that the brake lines plug in to then go out to the front and back brakes. its 69 mustang if that helps any.

 

I bought my swap kit on ebay, it came with: dual bowl MC, power booster, new push rod for the brake pedal (first one I received was too long so I had to order another one), new distribution block, 2 lines from the MC to the distribution block, brackets for mounting the booster on the firewall, obviously the front discs and the flex lines- I do not have a proportionnal valve but my set up is working great, I love it, such a difference!

Couple of tips:
1) For the power booster, if you did not have one before, make sure you cut the firewall opening big enough for the booster to go through nicely
2) If you have a manual transmission, I had read some articles stating such a kit would not fit due to the proximity with the clutch pedal ... it does work, just work patiently and look closely!
3) Bending brake lines and flaring is no fun ! can be done though ... I used some compression fittings that work very well so far
4) There is not much room to work in this area - if you do not want to get very frustrated you may have to take out your export brace and potentially the hood ...

I will post some pictures tonight when I get home ... good luck!

 

Compression fittings... if you're talking about fittings that have the brass ferrule that slips over the tubing, and then the nut is tightened down over it....this is NOT safe for brake systems. They can release and you will lose your brakes. Only automotive double flare fittings should be used in brake systems.





Proportioning valve, distribution block, combination valve...there are several terms that get thrown around interchangeably. Here's some definitions:


METERING
The metering or hold off valve is used in the brake system to better balance the front to rear brakes. The valve does not allow the pressure to rise at the front disc brakes until the pressure at the rear drums has risen sufficiently to overcome the brake shoe springs. At this point the valve opens to allow full pressure to build at the front brakes.[/align]
PROPORTIONING
The proportioning valve modulates the pressure to the rear brakes. The modulation is necessary to minimize rear wheel lock up found in heavy braking and to compensate for the differences in braking conditions in front disc / rear drum systems. As pressure is applied to the system full pressure is allowed to the rear drums up to a certain point. Beyond that point the pressure to the rear is reduced preventing rear brake lock up.[/align]
RESIDUAL
There are two different residual valves. A ten pound residual valve will maintain a line pressure to the rear to keep the drum brake shoes out close to the drums giving a higher firmer pedal. Without a ten pound residual pressure to the rear you will experience a spongy pedal. A two pound residual valve is required whenever the master cylinder is lower than the calipers to prevent backflow of fluid from the calipers to the master.[/align]
COMBINATION
A combination valve incorporates metering and proportioning into one valve. These are available for disc/drum or disc/disc systems.[/align]
ADJUSTABLE PROP VALVE
The adjustable proportioning valve is used when you have a special rear condition that requires higher or lower pressure than a normal condition. You sould always use a metering valve to the front when using the adjustable.[/align]

 

James! point well taken! safety first! ... car is in the garage right now so I'll buy a new set of lines and throw out the fittings