68 Charger converting from power to manual brakes

[91r/t]

Recently built a stroker with lower vacuum for my charger and am thinking of switching to manual brakes. I have front disc and rear drums with the 15/16 bore master already, so I believe all I need is the firewall stiffening plate for manual brakes and the rod that goes from the pedal to the master. I would end up removing the cam like piece that it uses to push on the rod from the power booster to the pedal as well I am assuming. I have 4 wheel drums with manual brakes on my '68 Runner and I don't mind them at all so this won't be a bad switch in my eyes. I am going to try them as is, but I lose vacuum after a couple pedal pushes now, so I am assuming it'll only piss me off more in traffic. The motor makes about 9" of vacuum at idle and I don't wanna go through the crap of adding a vacuum pump and all that. I am all about it being simple as its a '68, not an '08. Any other parts that you guys can think of that I am missing?

 

[gkent]

The m/c bore is too small in my opinion. You should use the 1.062" bore.

The small bore will give you a soft pedal BUT it will have to travel too far to fill the calipers/cylinders. The larger bore will give you a firmer pedal but less travel. The 1.032 seems to be the happy medium. Any larger and it takes a ton off leg effort.

You need the firewall plate and an adapter plate if you're using a late model aluminum m/c. The late model m/c's are 2-bolt whereas the plates are 4-bolt. Also, the hole in the plate is too big.

Buy an adjustable brake rod. Don't forget the little rubber piece that goes into the m/c cup - it keeps the rod from falling out !!

 

[91r/t]

The m/c bore is too small in my opinion. You should use the 1.062" bore.

The small bore will give you a soft pedal BUT it will have to travel too far to fill the calipers/cylinders. The larger bore will give you a firmer pedal but less travel. The 1.032 seems to be the happy medium. Any larger and it takes a ton off leg effort.

You need the firewall plate and an adapter plate if you're using a late model aluminum m/c. The late model m/c's are 2-bolt whereas the plates are 4-bolt. Also, the hole in the plate is too big.

Buy an adjustable brake rod. Don't forget the little rubber piece that goes into the m/c cup - it keeps the rod from falling out !!

Using a stock style 4 bolt master cylinder, so that mounting plate shouldn't be an issue. I believe Dr. Diff says that's the size master bore (15/16") to use for manual discs.

 

[R/T Boy 67]

I recommend going to manual. Super easy to do in your case. Plate and pushrod is all you need. If you don't like the small bore master, then change it to a larger one. As Stanton said, don't omit the rubber lock ring.

 

[Billccm]

I agree with the 15/16 master for manual front disc. I'm running the Dr Diff kit with 15/16 and very satisfied with the braking.

 

[91r/t]

Anyone got the manual stiffening plate, rod, and rubber lock ring around they wanna sell for the 68 B body?

 

[1967coronet440]

I was told to use a 7/8 bore on my front and rear disc. Wondering if I made the right choice now.

 

[91r/t]

To me, even a softer pedal and a bit more travel is way better than the feel of old school power brakes. I’d rather breathe on them to slow and then push to slow faster. Both my cars are stick cars so when I let off they slow down anyway. If I wanna drive like a complete Nimrod, I guess I’ll jump in the new car for that. Simpler then better for me!

 

[PP1RT]

Anyone got the manual stiffening plate, rod, and rubber lock ring around they wanna sell for the 68 B body?

Contact CornpatchMO on here. I gave him parts for a swap from manual to power swap. He should have what you would need i think. (68 sport satellite)

 

[91r/t]

Contact CornpatchMO on here. I gave him parts for a swap from manual to power swap. He should have what you would need i think. (68 sport satellite)

r413 hooked me up! Should be an easy swap and that will take care of my low vacuum assist issue. Really didn’t wanna start wiring in vacuum pumps and creating more crap to go wrong lol.

 

[Frankb]

I went manual from power on my 69 GTX. Car had drum brakes front and rear. Bought a complete kit with 11 inch front disk. Kept the drums in back. Car had the bigger drum brakes from factory. I'm very disappointed with the brakes. In a word they suck. Pedal is rock hard but brake action is not good. It takes a lot of pressure to make car slow quickly. MC is 15/16. Trouble shot until I was blue in the face and just decided to live with it.
Frank

 

[Billccm]

I went manual from power on my 69 GTX. Car had drum brakes front and rear. Bought a complete kit with 11 inch front disk. Kept the drums in back. Car had the bigger drum brakes from factory. I'm very disappointed with the brakes. In a word they suck. Pedal is rock hard but brake action is not good. It takes a lot of pressure to make car slow quickly. MC is 15/16. Trouble shot until I was blue in the face and just decided to live with it.
Frank

What kit did you use.

 

[Sweet5ltr]

15/16" is definitely the correct size MC for Dr. Diffs manual front and rear brake applications (works excellent with my setup), but Cass has this down to a science and really knows what works.

You're going to want to gut the factory distribution block for a front and rear disc swap. Install a proportioning valve into the rear line. With a front disc / rear drum application, it gets even more difficult, as the owner needs to verify what calipers they're using (obtain specifications), call a reputable company and go from their. May take a few MC bore sizes to get the proper pedal feel without diving too deep into it.

https://www.onallcylinders.com/2014...figure-pedal-ratio-master-cylinder-bore-size/
Summary from the article above;
So, if your car needs some help in the stopping power department, or if there’s a need to reduce the pedal effort, you have a few options: A) decrease the master cylinder bore size; B) increase the pedal ratio; or C) increase the wheel cylinder bore size. If the pedal ratio is increased, there will be more travel at the master cylinder piston. If the master cylinder bore size is decreased, the piston has to travel further to move the same amount of fluid. Typically, a master cylinder has approximately 1-1/2-inch to 1-3/4-inch of stroke (travel). What you have to do is coordinate the pedal ratio with the bore size to arrive at approximately half of the stroke (roughly 1-inch) in order to make the brakes feel comfortable and stop the car safely.

 

[Sweet5ltr]

I was told to use a 7/8 bore on my front and rear disc. Wondering if I made the right choice now.

No you may not be wrong, the MC bore sizing is only relevant to your specific braking package (caliper bore / piston surface area).