Porportioning valve

I'm converting my cousins 68 Cyclone from drums to power discs. Do I need a new porportioning valve or are they the same? Also would a booster from the Mustang (same year) work? Any insight would be greatly appreciated.

 

From what I read on the internet and what I researched on my own. The only main difference between the combination valves is the way it mounts to the fender apron. Some think the spring that controls rear brake proportioning is different between a big heavy car vs a small light car. A member on TFFN said he took about a dozen PV's apart and he didn't see any difference in the spring. With that being said, I think you should be good with using the '68 PV but you will need a disc/drum master cylinder because the drum/drum MC will have a residual valve and this valve will keep too much pressure on the front brakes. I don't know about using a Mustang booster

 

Heres a quick read, you can make up your own mind.

BRAKE PLUMBING

 

The guy I quoted from TFFN is the same guy who wrote the article in the pdf. The pdf was written back in ’08, The quote was written 2-1/2 years later

 

The original '68 disc brake cars had a separate residual valve in the line to the rear brakes.

 

We have a 1969 Cyclone at work, I am pretty sure that the booster uses a lever rather than a straight push rod like a Mustang. If it isn't sold tomorrow, I can take a photo.

1968/69 Torino/Cyclones are basically the same mechanically.

From my research on OEM brake distribution blocks, drum and disc brake blocks are different. JMG is correct in regards to the diffential valve on a disc system.

Fine Lines or Classic Tube likely make new brake lines. Drum and disc hard lines are generally not intercheable on the Ford/Mercury cars that I deal with (1967-73 Mustang and Cougar).

Plenty of folks have success plumbing in an adjustable proportioning valve with their drum brake hardware.

 

Thanks for the info everyone. Since this car is all drums would the check valve be at the master cyl as indicated in the article? I found a porp. valve from Dearborn classics I believe will fit this application. Also the drum set up uses a straight rod to the pedal. If I use a booster w/ a rod instead of the lever I'm thinking it should work. Please tell me if I'm wrong.

 

This is what the OEM residual valve looked like. It goes inline between the distrubution block and the rear brakes. If you are using '68 Cyclone discs & a '68 Cyclone MC, there should be no need to add an adjustable valve. You can buy aftermarket residual valves cheap, that funtion just like the oem one.