Adding Power Brake Capability

[ernie d]

Hi everyone,

My 69 coupe has manual brakes. Although it is 4 wheel disc, the stopping power is awful. Am seriously thinking of adding power brake capability.

What I am intertested in getting feedback on - what are the changes I will have to make to do this conversion? Obviously, need to buy the booster itself.

What else? Can I use my non power master cylinder on the new booster? Do I neeed to change the lines, or simply reroute them to the new master cylinder location?

Appreciate your insight to this, thanks

 

[chevyaddict]

Hey there ernie! I'm not sure about vettes in particular but given you are working on a 69 chevy I know that the master cylinders for power brakes are different than manual (at least on other chevies). The shaft length that hooks to the break pedal is also a different size so you'll want to retrieve a new one of those as well. Aside from that, just connecting up the vacuum line should be all that is required as far as I know! I added power brakes to my 68 chevy truck.

 

[Space Cowboy]

I'm adding power brakes to my 68 as well. I bought a single unit chrome Booster and Cylinder from Jegs. For the price they were the cheapest. If you're not going for the chrome look, of course it will cost even less. I was unaware of the longer shaft length... Dawn, do you know what that physical part is called. I'll need to hunt one down.

 

[chevyaddict]

No, I sure don't. Again, this may not be the case for Corvettes in particular, especially since vettes have calipers all the way around. It is the case for camaros and the older trucks. Hopefully others will post here and either confirm or disconfirm that statement!

Dawn

 

[Space Cowboy]

Okay, thanks Dawn...It's still important information to ask about. Does anyone know about a longer shaft for power vs. manual brakes on a 68 or 69?

 

[cwerve74]

I looked at this conversion very closely for my 74. The master cylindar has a different bore size. The booster needed a couple of additional mounting holes. The brake lines are a different shape. Same size just connect more forward and the ones from the manual don't reach. Lastly the hard part. The rod that connects the master cylindar to the pedel is slightly lower and requires a diferent mounting point. On the 74 you got this by flipping the bracket on the brake pedel. The space to do this is almost impossible to work in. I beleive that is the hardest part of the conversion. Why did't I convert you ask? Well once I got the wheels and rotors straight which included new wheel bearings. The braking power increased to a point I was no longer interested in the conversion. Good luck.

 

[Glen Braxton]

I did a power brake conversion in July, on a 1970. The are several things to consider. The master cylinder is different, no two ways about it. When mounting the vacuum booster, the bottom two bolts will go into two holes that have bolts in the standard brake car. Knock the bolts in to the interior. The upper two bolt that secure the standard master cylinder had to be knocked in also. Now the upper bolts on the booster dont match the upper bolt holes I just exposed. I had to mark and drill two new holes above the existing holes. Next the hole where the master cylinder shaft passes through, doesn't match up with the booster. Studying the AIM in the very front section I saw that a optional enlarged hole is there for the booster. The steel plate behind the firewall, has the correct size hole. I enlarged the hole in the fiberglass firewall to match the hole in the steel backing plate. Do that and it matched up fine, just like in the AIM. Next problem is connecting the shaft. The booster being centered lower, the shaft mounts to where the brake light switch paddle mounts on the peddle arm. Remove that paddle, mount the shaft in that hole. Now the power set up needs a longer paddle, available from CC, Zip, Paragon, etc. The New power switch paddle mounts in the hole where the standard brake mc shaft mounted, one hole above where the power shaft is mounted. It tight under there, even with the dash removed.


All in all, a well ajusted standard brake car seems to stop as well as the power brake car.

 

[norvalwilhelm]

IF you have power steering don't waste time on a vacuum boost, go directly to the hydraboost. It is a far strong unit, compact and easy to install. While the none power master cylinder needs a slight modification to fit the power master cylinder is a direct bolt on.

 

[Space Cowboy]

I don't quite understand your message norvalwilhelm, but just to add... I spoke with a guy at Wilcox yesterday and he said that you could make your own shaft. Should be able to make it out of steel flat bar. It only needs to be approx. 2" longer than the origninal.

 

[ernie d]

Norval,

I'm not familiar with Hydraboost. What is it, how is it different from a traditional power booster, how does it work, where do you find it, about how much? Sorry I'mm asking so many questions, but.......

Thanks

Ernie

 

[pgtr]

PBs do NOT improve "stopping power!"

PBs do NOT improve "stopping power!"

I agree w/ cwerve74 - a properly setup manual brake system works great and you may find that is all that's needed. In addition to the brakes/rotors cwerve74 mentioned I'll add to check/replace hoses and ensure pads as well as hydraulics are in proper working order. I too am sticking w/ manual brakes on my 4 spd C3.

 

[tomtom72]

Hi all, IMHO I agree about fixing the system. My 72's system was toast, the calipers had rust pits in them and the car was only 5 yrs old at the time. The advice from the two ASE guys I knew was expensive, but wow what a difference. My car had manual brakes too. tt72

 

[ernie d]

OK, I guess I've heard from many of you that manual brakes are quite good when properly set up. Apparently mine are not well set up. They aren't spongy so its not a bleed the brakes thing. Pedal is nice and firm, no extra travel of pedal required, but........they just dont grab quick enough.


So since so many of refer to manual brake "setup", do you know of a good link to details of best setup for manual brakes?

Thanks

 

[BruceBed]

I tried to do this recently on my 73. The biggest problem my mechanic encountered was that the firewalls are different on p/b and non p/b. I thought it was a reasonably easy thing to do when I called Eckler's to get the parts. I wasn't succesful in the installation and in the end I left my car non p/b. If interested in why, email me and I'll tell you the whole 9yards..........

 

[BruceBed]

This is the same problem I encountered. In the end , it just wasn't worth doing that much work.....

 

[JohnZ]

Not worth the grief, IMO - with OEM organic pads, the non-power system works just fine. If someone has replaced the pads with semi-metallic or "race" pads, they require much more pedal pressure (and are unnecessary).

 

[BarryK]

I have to agree with everyone else on this thread so far.
When I got my '65 back in March it only had standard manual brakes. I was concerned about that to be honest because I never drove a car with manual brakes (only having had newer, modern cars before). But except for a slighter higher effort required on the pedal, and really not much more at that, the stopping power is excellent. In fact, after drive the car for only a short time I didn't even notice that they are "only" manual brakes anymore unless i get out of the Vette and immediattely jumped into another car with power brakes. remember, the brakes on these cars are actually pretty good (unless they made any major downgrade changes from my '65 to your '69 which i doubt) and the cars are light weight. That should equate to excellent braking performance.
You may want to get you car into a GOOD brake shop, make sure everything is set up properly, the rotors are nice and straight, and you have the proper pads installed. As JohnZ said, using the wrong pads will decrease your braking performance.

 

[norvalwilhelm]

Norval,

I'm not familiar with Hydraboost. What is it, how is it different from a traditional power booster, how does it work, where do you find it, about how much? Sorry I'mm asking so many questions, but.......

Thanks

Ernie

Hydroboost is used on most diesel trucks and vans, Diesel engines don't generate vacuum so instead of vacuum assist they go to hydroboost. It runs off the power steering pump. Your pump puts out about 1000 psi of oil pressure, why not use it to stop the car?? The hydroboost units from 80's and 90's trucks and vans are almost a bolt in deal for our cars. The linkage is too long so it needs to be cut and have a 3/8th die run over it but thats about it to make it fit. A stock POWER master bolts right up, I used a non power unit but had to slight modify the rod.
I paid $20 for my first hydroboost and $50 for the next. My last unit came out of a 94 one ton truck GM. Ford also uses hydroboost.
It is very compact , extremely rugged and gives fantastic stopping power. If it can stop a one ton truck , gross weight about 10,000 lbs it can stop your vet.
I paid $50 for the used unit and about $100 for the lines.
YOu need to have a power steering pump.
Manual brakes suck and I was always embarrassed when others test drove my corvette until I got hydroboost and now I warn everyone about the extremely powerful brakes.
While Performance friction metallic pads stop great after warming them up they eat rotors so I stick to organic pads.
Hydroboost is the way to go. You can buy complete bolt on kits, everything included for about $500 roughly from a supplier on corvette forum.
The units are the only way to go.

 

[pgtr]

It is very compact , extremely rugged and gives fantastic stopping power. If it can stop a one ton truck , gross weight about 10,000 lbs it can stop your vet.
The units are the only way to go.

Using a common definition of the term 'stopping power' being a measured ability to stop a car - The system outlined above simply does not improve stopping power over std or power brakes. But I tell you what... I bet the pinky toe on my right foot could stop a vette just like that hydroboost! That same toe might even stop that same ol truck too.

While I find the pedal assist system interesting..., I don't care if someone hooks the hydraulic actuation on their C3 brakes up to the Hoover Dam... FACT: Same rotors, same pads, same swept area, same tires and same vehicle weight EQUALS SAME STOPPING POWER.

If your thing is to have incredibly minimal PEDAL EFFORT with lots of pedal assist from a (parasitic?) pump out of need or preference - that's great and I'm impressed by the solution. Personally I feel a sports car needs to give a certain amount of feedback to the driver thru steering, pedals and what not and would personally be leery of too much isolation - but that's just me.

My point is simply this: Let's not confuse pedal assist with stopping power.

--------------------

Food for thought: The C2/C3 brake system was an engineering high point when it was introduced and after 17 years of virtually unchanged production usage, in many ways still is 20 years after end of production. With it's 4 wheel discs, vented rotors, 16 floating pistons - it was nothing short of top of the line for it's era. Today you mostly see lots of 'cheap' unsophisticated single piston floating calipres on so many cars. Try this little test: Compare a non-Corvette 1965 vehicle of similar weight w/ manual brakes to a properly setup C2/C3 also equipped w/ manual brakes. Power brakes became a widely popular pedal assist option in Corvettes by the early to mid 70s as a luxury option somewhat in conjunction with the popularity of the automatic transmission to largely accomodate a change in the preferences of the buying public.

More food for thought: Nothing wrong w/ factory PBs, but if a pedal assist is 'overdone' there is a potential risk that it may become more difficult for the operator in performance driving scenarios to modulate the brakes at or close to the threshold of lockup.

 

[norvalwilhelm]

Just a picture of the hydroboost. I actually took this picture for someone else to show the 85 one ton hydraulic master cylinder using to convert our older cars to hydraulic clutches.
The hydroboost has the brass canister on one side to a one time power stop if the motor quits but after that it becomes manual but not with the hard pedal that the vacuum units have.