Wyze

I've been cleaning these up so I can paint them and installed!!!!
They came from a car with PB but I'm thinking about staying manual!!!
d920571f.jpg

My question is, can I get a manual Disc brake master cylinder????
And what else would I have to get or change for this conversion on my 68?????


Thanks Drew

Rickman48

DON'T GO MANUAL DISCS!!
Only car I ever drove with manual discs was a Mustang 350GT-H, and I thanked god it was automatic, as it took BOTH FEET to just slow down from a buck!!
Even if you've a big cam, get the can, as non-power discs coud be fatal, IMO!!

Wyze

It's already manual drums!!!!
Anything has to be better!!!! Lol!!!!!


PS, I will be adding a booster later in time but I was trying to get her back on the road for now!!!!!!

Rickman48

Manual drums are engineered to be as they are with the correct master piston to wheel cyinder ratio.
Manual discs were never an option - require more pressure!
Ever try to stop a power brake car after the engine died? You're better off with the E-brake!

firefrost gold

w-30 had Manuel disk brakes so did some corvette .

joe_padavano

And, of course, THAT info is applicable to an Olds...

My 1970 W-30 has factory manual discs and it stops just fine. You will need the correct manual disc master cylinder, since the bore diameter is different.

507OLDS

I have manual discs on ever car that I own,either factory or converted.There is absolutely nothing wrong with this.I have gone from both power drums to manual disc,and power disc to manual disc,and I have had NO problems with stopping,and there has been NO extra effort needed to do it.If there is,you are doing something wrong.I have also owned a fair share of foxbody mustangs,and converted them to manual brakes,which were either front disc or 4-wheel disc,and I didn't have any issues with those either.
Depending on your type of brake system,you will need to choose the correct master cylinder.This will often dictate pedel travel & pedal feel.It is volume vs pressure.On cars like my 72,I just get the correct manual disc master cylinder for a 72 Cutlass/442.That car has the factory rear drums,with 12" B-body front rotors.Another thing to know about the A-body brakes is the brake pedal itself.If you look at the brake pedal,you will see 2 different holes drilled in it.The lower hole,closer to the foot pad,is for power applications.The higher hole,closer to the pivot,is for manual applications,giving more leverage.A common mistake is to put the rod clevis back into the hole that it came from,which will have a direct effect on how the brakes reaction & feel.If you crawl up in there even further,you will notice there are a few different postions to mount your stop light switch.You will need to move this to another hole selection to get the switch to operate as it was.This isn't anything difficult.
On your 68,if you aren't concerned with originality or correct appearing,then I would just get a 71-72 style disc proportioning valve,and 71-72 master cylinder.If you want everything to look correct,like a 68 W30,then you would keep your existing lower proportioning valve,and get the correct 68 upper combination valve that mounts next to the master cylinder,and get the corresponding master cylinder for a 68 manual disc car.
That rotor with the groove is a factory piece,and a nice touch if your are trying to make something look correct.

Lady72nRob71

You can go with manual discs temporarily until you get time to finish up with adding the booster.
Just keep a safer distance from everyone, start braking earlier, and learn how they work on a deserted road.

This is true.
However, if one went with non power discs, the master cyl. clevis will be in the upper brake arm hole which would give more leverage, and require less pedal effort.

joe_padavano

I'm sorry, but there is a LOT of bad info in this thread. Mustangs, Pintos, and power brake cars with the engine off are NOT a Cutlass with factory manual brakes and that experience is absolutely NOT applicable. Unless you've driven a factory manual disc brake car, your experience does not apply. A power brake car has both a different pedal ratio and a different bore in the master cylinder, which is why that doesn't apply to factory manual brakes. Brian's is one of the few posts on this threat that has it right.

monzaz

Well I can add that if you are installing all this to disc you might as well go the extra step to power as it will sure make the car more comfortable to drive and a plus on the selling side....if you ever have to.
This is where technology is a huge plus EVEN IN late seventies technology of power disc.
There are a multitude of companies that sell the booster, correct master, P valve and pedal push rod length parts. Prices have gone down and are reasonable and making it easier to get then having to scrounge for used 50/50 working used parts.

If you have a BIG HARRY cam with gobs of over lap I can totally understand the manual brakes and IF your car already has good working manual brakes...OR you just plan think it is cool. IT IS YOUR car you do it the way you like.

I would say from memory of 10 year ago...you will need a different master with the manual disc and the Proportionate valve and you might need a different length pedal push rod into the master also. Hope that helps.

Jim

Rickman48

Sorry about the Muskrat post - but it was a scary experience not wished apon others!
There was a dash tag about 'pedal effort' but was fine at low speed.
Hoped he just wasn't removing the booster - knew that was wrong.
Never knew about manual discs on an Olds - love learning new things!
Thanks Joe!!!

507OLDS

Cars like my 70 W30's and my 70 W31 never had a booster,and can't because of the lack of vacuum.My 72 has that big honkin cam,ground on a 106,and I never intended on having power brakes with it anyway.Even my 180,000 mile daily-driver 70 cutlass I had for many years,I converted to manual discs.I like everything as plain & simple & clean as possible.Yes,it is a preference to me,but by no means does it take any extra effort to stop,as some have claimed.In general,the correct master cylinder does play a big part in making it all work.A master cylinder with a 1" bore will give more line pressure & more pedal travel,whereas a master cylinder with a 1 1/8" bore will have more volume & less pedal travel.I have found this to be more critical when converting to rear discs,but that is another story for another day.

80_cutlass

I have manual disc from the factory on a Dodge PU (I know its not the same as a cutlass) but they work great. I used M-body brakes to do a disc brake conversion on my barracuda (and I know its not a cutlass) and used them as manuals with the M-body master cylinder and the propotioning valve: worked great.

So, in my experience a well thought out plan using manual disc brakes works fine. One of my examples is factory the other is a conversion, but both good experiences.

sb

Wyze

Thanks guys!!!!! So my lines won't need to be changed for the new master cylinder????
As some of you know I bent my control arm and have to change them!!!
So I figured since I've always heard how much difference disc makes, and I'm gone be in the area I might as well do it now!!!!!! Lol!!!



Oh & Brian, I'm gonna start with these rotors but I'll be switching to drilled & slotted when I get my income taxes!!! Lol!!!!



Thanks to everyone!!!!
Drew