[KEN CROCIE]

Corvette's came with MANUAL 4WD. Power was an opt
70 camaros and firebirds came with MANUAL disc brakes. Power was an option.
I write this because I constantly hear "I'm converting to disc brakes, what booster do I use?"
On my first disc brake conversion, I used the stock 64 GTO single master.When went to 4 Wheel disc, I used the 68 Corvette dual master cyl.
Based on cost effectiveness, I would just swap out the existing booster for the dual dia. 9".
Manual is my first choice.

[Scarebird]

The dual unit Ken refers to is good down to 9 InHg.

We had a fellow Pontiacer whose 11" booster was not doing it, the dual 9" did.

[NeighborsComplaint]

Originally Posted by n20ta2

I just installed a leed black bandit vacuum pump for the power brakes on my 69 gto. It holds vacuum well but I really dont have good brakes even with the pump. The complete system is new and completely stock including all lines rubber hoses ,calipers and rear wheel cylinders. I did install an 8" booster in place of the stock one for more clearance for the highports, could the booster be the issue? It almost feels like non power breaks at this point. I also used a new stock replacement perportioning valve from inline tube.

I've been through an A body 4 wheel disc conversion and will share my experience.

Those "flower pot" boosters like you have don't work very well if at all. You probably have a single diaphragm unit and I'll bet you have to "two-foot" the brake pedal in an emergency stop. That's how mine was with the stock 11" booster. The prior owner had converted it to front disc brakes using the original master. I could tell he had cobbled it together, extending the tiny existing front hardlines with "pigtails" held on by compression fittings. It was a real butcher's job. After I got it running again and road tested it, I described how bad the brakes were asked how he ever drove like that. He replied "Yeah, it always had a hard pedal from the cam, I even ran into the back of some guy's Corvette in the registration line at the Street Rod Nationals" like he was proud of that." I limped along with lousy brakes for a while always mindful of needing plenty of room to stop and avoiding stoplights on hills.

I eventually converted it to 4 wheel disc brakes with all new OEM replacement calipers (Cadillac rears w. integral parking brake), new lines, hoses, GM prop valve, Corvette master and an 11" Delco Moraine booster. It was worse. It wouldn't hold on hills and would push through the brakes at stop lights in traffic. I still have nightmares from that.

I wound up putting on a 9" dual diaphragm booster intended for a 1980 Turbo Trans Am. It bolted right in place and connected to the pedal linkage. I had an excessively long pedal travel but good stopping power. I swapped out the furnished short pushrod that came with the master cylinder for the long one (that was both an ah-hah! and doh! moment, I should have known by the length of the booster (dual diaphragm) it needed the longer internal pushrod. Now the car stops like a normal car with power brakes.

My engine vacuum at idle is 11".

[n20ta2]

It has to be the booster, the vacuume pump pulls more then enough. I may try the t/a booster at this point as its probably cheaper then converting to manuel.

[GOAT8U2]

After you have a hard pedal and miss a bad accident by inches, you'll spend what I did for your car to brake better than new cars.

9" dual diaphragm
Hella UP28 vacuum pump at 20"
Aerospace 4 disc front and rear brakes (rears added later)
SS lines

Stops better than my daily 09 Lancer that's 600lbs lighter.

Picture is with high ports and KRE valve covers.

[chuckies76ta]

Originally Posted by GOAT8U2

After you have a hard pedal and miss a bad accident by inches, you'll spend what I did for your car to brake better than new cars.

That statement got my attention. I had this experience with my car years ago before upgrading to a Hydraboost unit. I took my brother out for a drive and as you know how things go I was showing off. I accelerated very hard and was coming up to a traffic light and put the car in the intersection too much for my liking. Scared the **** out of me. It didn't matter how hard I pressed on the brake pedal, it was not gonna stop. I was so pissed at myself. I poured all this money into a car that I can't stop.. I know it was stupid. Reminds me of that video posted awhile back when the guy had the accident in the intersection and people got hurt. https://www.youtube.com/watch?v=5oO226PgSkg
All I know is this from my experience. It's no fun driving these cars wondering if you'll be able to stop when in an emergency situation. period. I don't care what it cost or how much work you have to do or what parts you need to get the job done. You need the piece of mind knowing you can control your vehicle at all cost.

Same reason I upgraded to a TKO-600 transmission, after being stuck at an intersection and the 40 year old gear box wouldn't go into first gear. The point is, Get you car driving the way your comfortable, and knowing it safe, so you can really enjoy it every time you take it out. Just saying.

[Don 79 TA]

just tossing this out there, disregard if it sounds idiotic.....

what size bore diameter master cyl are you using?
i went with the 1" one over i think the 1.25 or was it 1.5, i don't recall
but it certainly helped my situation greatly
the pedal is so much better, i use a small i think its 9" single master with the CVR electric vacuum pump
wasn't that much $$ either
also do ensure you have no air trapped, it can be a real PITA if you have an issue like that
boy, reverse bleeding helped that issue i had when i redid the whole brake system

and could it be your brake pad compound too? that would be more inline with stopping, maybe not so much as a stiff pedal
the master cyl changed helped that pedal stiffness, and make sure you dont have a tisted caliper hose or something like that (NOT saying anything else about that..... you live and learn as a kid)

i know some folks have used i believe they call it the mopar style master 15/16 or something like that

just another idea possibly to help??????

I agree going manual would "clean" the looks up and aren't really that bad when setup correctly
only hydro experience i have had is with big trucks, so i can only image how awesome for a street car they would be
be sorta like the time i jumped into my 4wd probe after a brembo brake upgrade, used to whacking the brake pedal, after the overhaul..... HOLLY CRAP...... the windshield wanted to make out with me, took me by surprise

one last thing..... i remind myself everytime i get back into the TA after the winters rest, is to remember.... it DOES NOT stop like the wifes new Honda Accord (which i ABSOLUTELY LOVE).... or her Corvette (Z51 brake option).... you get used to those, and then you go back into the old.... WAKE UP call lol

[george kujanski]

I had a '67 Lemans Sprint 4 drum manual system way back. A panic stop at speed was scary due to brake fade.
The current GTO had 4 drum manual system also. I added an 11" booster and it was ok, but still had brake fade, plus i didn't like the firewall clutter (clutch issues).

Went back to manual brakes with a GM front disk upgrade and eliminated fade as expected. At the time I was looking for a master that had a 7/8" master piston but couldn't find a GM version. WIlwood has a 7/8" and I may opt for that as a further improvement. I have no issue with he feel of manual brakes.

George

[Formulajones]

I daily drove the 56 nomad for years. 4 wheel manual drum, and that thing is a tank. Actually I got used to it, and comfortable with it. Yeah brake fade is a problem if you get the thing rolling and really want to stop fast but most of the time I drove it sensible and within it's limits. If I didn't I would have wadded that thing around a tree 40 years ago and might not even be sitting here today.

Yes, it still has 4 wheel manual drum brakes LOL

Honestly it could use an upgrade and I might do disk swap on the front of that one some day, but it'll stay manual.


The other classics are typical power front disc brake setups that were stock issue, and they stop very well as long as the engine produces the proper vacuum to run the stock booster. I don't find any need at all to upgrade anything there and we are daily driving them that way. They'll lock the tires up in a heartbeat if you want to, so to me the brakes are already overly adequate.

Hydroboost on the cars that have engines that don't make any vacuum and had power brakes to start with, and I have no regrets with that change. Pedal effort is incredibly light and will stop both 4,000 lbs. cars easily with the stock disc/drum brake setup. Again they'll over power the tires and slide with little effort.

Seems to me like tires start to become the limiting factor, even with stock brakes.

[n20ta2]

Im using a a stock replacement master, I have a good brand new leeds vacuume pump pulls 20" of vacuume no problem. I'm now sure its the booster after messing with it yesterday. I'm going to go with a 9" duel trans am booster and see how that works, I will at some point upgrade to 4 wheel disc's probably aerospace as I have used them in the past. This booster must just suck, it holds pressure fine just honestly has minimal to no assist.

[Scarebird]

Originally Posted by george kujanski

..Went back to manual brakes with a GM front disk upgrade and eliminated fade as expected. At the time I was looking for a master that had a 7/8" master piston but couldn't find a GM version.

George

Not going to find 7/8", too small anyway. Try the 75-77 Monte 15/16" manual unit:

https://www.napaonline.com/en/p/NMCP...pressionRank=5

[KEN CROCIE]

Agree with Scarebird. 15/16 is the ticket

[george kujanski]

Thanks for the info guys.......I'll look for it. BTW Wilwood claims they have a 7/8" unit. Pricey, but not unreasonable for a new one, i guess.......

The Monte unit looks like it's got the a$$ backwards reservoirs. Mine is configured for front res = front brake. Would need to redo my stainless lines....

George

[Scarebird]

Originally Posted by george kujanski

...The Monte unit looks like it's got the a$$ backwards reservoirs. Mine is configured for front res = front brake. Would need to redo my stainless lines.

George

The reverse reservoirs are actually a better setup engagement wise.

[george kujanski]

Well, crap. I just realized my brakes work just fine!

george

[65madgoat]

Absolutely love manual brakes. Had hydroboost. No thanks.

With so many brake pad compounds today, manual brakes can be tailored to what you like or want.

[mchell]

For those that have converted a power disk/drum brake system to manual. What exactly were the parts needed? Where were they sourced? Kit available?

I assume a new master. Can the existing pedal be used? Need a different rod length for master? What about the firewall bracket? I assume a new bracket to convert power booster mount to a manual master?

anything else?


thanks

[MatthewKlein]

Originally Posted by mchell

For those that have converted a power disk/drum brake system to manual. What exactly were the parts needed? Where were they sourced? Kit available?

I assume a new master. Can the existing pedal be used? Need a different rod length for master? What about the firewall bracket? I assume a new bracket to convert power booster mount to a manual master?

anything else?


thanks

Haven't installed it yet but I think this is all you need

https://www.summitracing.com/parts/DHB-M76162

This was for a '72 LeMans unsure what other years it would work for. Been a while since I did the research. Large reservoir is for the disc. Small for drums.

Another edit:
On some of my other cars I've needed to add an extra proportioning valve to keep the rear brakes from locking up during hard/panic braking

https://www.summitracing.com/parts/WIL-260-8419

More editing:
Now after reading more this might not be the correct bore diameter after all.

[Scarebird]

it is 1.125" - too big for manual.

mchell: what car is this going on?

[MatthewKlein]

Cyl #M76162 is 1 1/8 bore dia. Sounds like the larger the bore dia the harder the pedal effort.

There are 2 holes in the brake pedal. Upper is for manual, lower for power. Unsure if a different length push rod will be necessary