whats wrong with my brakes?

[67_camaroRS]

1967 camaro, Running disc brakes on all four corners, Wilwood 6 pistons on the front and 4 pistons on the rear. Stock steel brake lines and Wilwood flexlines. I have a dual diaphragm brake booster. I'm not really sure what master cylinder it has on it though. I'm running a BB 396 with a big cam. The car just doesn't stop quick enough. for all that brakes I got, I feel like the car should stop faster and on a dime :mad: . I bought the booster and master cylinder as a kit a while back and I don't remember the specs. I don't know much about brakes and all that jazz. I just remember somebody telling me to remove the proportioning valve and that will solve my problem. :getout:

thanks, Albert.

[Tinker]

I would suggest reading many of the threads in this brake category, starting with "I give up on bleeding my brakes". Your question seems to be a popular one. If that doesn't work, you need to be more specific on your system, including master cylinder bore size and caliper piston areas. The proportion valve should be there to limit rear brake force only. Removing it will not help overall force, unless it is incorrectly installed. I hope this gets you started.

[rickpaw]

You mentioned a big cam. Which means you may not have enough vacuum to operate the booster. IIRC, you need around 13-14 inches of vacuum for the booster to work properly.

Something to look into.

[Vegas69]

Agreed, you likely have 10 inches of vacuum or less at idle.

[67_camaroRS]

What do you guys recommend me to do?Clueless

[Tinker]

Try to find as many specs on your brake setup that you have now. Again, caliper piston area, master cylinder bore size, pedal ratio. You need to know where you are at before you can make a move. Do you have a vacuum gauge that you can check actual engine vacuum at idle? There are also pressure gauges available that screw into the caliper bleeder holes for checking actual brake line pressure. All these things are very important to the diagnosis.

[randy]

Stick a vacuum gauge on it since that is quick and easy and report back

[Vegas69]

Agreed

[GregWeld]

I WOULD NOT remove the proportioning valve.... you most likely need that -- and at the very least -- need to understand WHY you don't have good brakes before doing something like that.


You do need to do as suggested and check the vacuum - at the take off port for the brake booster.... at the engine. Or if you have a small vacuum gauge hose - at one of the other ports.

If you don't know how to do this - or don't have a gauge - it's a very simple (therefore should be super inexpensive) to have a shop do it for you.

++++++++++++++++++++

After you do that -- check the brake pedal ratio....

Here's a link to show you what that is:


http://techtalk.mpbrakes.com/how-to-series/correctly-calculating-pedal-ratio


+++++++++++++++++++++



Next --- open the master cylinder -- tell us if there is a larger volume between the two reservoirs.... the larger (if there is a difference) needs to serve the FRONT brakes -- and the smaller (if there is a difference) needs to go to the rear. You can simply follow the lines to find if they go to the front or to the back.



++++++++++++++++++++++



Did you BED the brakes after the installation?? Do you know what this means??

[67_camaroRS]

ok thanks for the help. ill check the vacuum and other stuff this weekend. ill get back to yall. :cheers:

[67_camaroRS]

I tested the vacuum with a tester and got about 9 inches of Hg Vac on idle. Got about 17 inches on 2000 rpm. the length of the pedal was 12 inches and to the master cylinder rod it was 4 inches which makes the ratio to 3:1 i believe.The master cylinders reservoirs were identical in length but the rear one is smaller from the inside. I did BED bleed the master cylinder when it was new. What is the next step? Vacuum Pump? or?

[GregWeld]

Good info.....


You really don't have enough vacuum for good power brakes.... Your idle vacuum is about HALF what you really need... and even at your 2000 rpm level you're only making 17"....

Pedal ratio is "okay" for power brakes -- but not when you have such low vacuum.

Also -- check that your booster is okay. With the car running -- apply the brakes --- hold em -- shut the car down --- your pedal should hold for about 30 seconds is the booster isn't leaking.

So Check that....


Then --- you've got a couple options....


Increase your pedal ratio to 4:1 or even 5:1 ---- if you can keep all things aligned properly....

Add an electric vacuum pump .....


Or junk that set up and run a good manual master cylinder and get your pedal ratio to 6 or 7:1 <this would be my choice>

Or go to a "hydraboost" boost system....

[craig510]

Post the piston sizes for you calipers and master cylinder. You will need the caliper piston area to determine ideal master cylinder size for a given pedal ratio.

[67_camaroRS]

Post the piston sizes for you calipers and master cylinder. You will need the caliper piston area to determine ideal master cylinder size for a given pedal ratio.

These are the Rear Calibers I have on the car:
http://www.wilwood.com/Calipers/CaliperProd.aspx?itemno=120-6806

Front Calibers:
http://www.wilwood.com/Calipers/CaliperProd.aspx?itemno=120-13429-BK

I bought them as kits Rear kit: Part #140-7578-D
Front Kit: Part #140-10510-D

[67_camaroRS]

Good info.....


You really don't have enough vacuum for good power brakes.... Your idle vacuum is about HALF what you really need... and even at your 2000 rpm level you're only making 17"....

Pedal ratio is "okay" for power brakes -- but not when you have such low vacuum.

Also -- check that your booster is okay. With the car running -- apply the brakes --- hold em -- shut the car down --- your pedal should hold for about 30 seconds is the booster isn't leaking.

So Check that....


Then --- you've got a couple options....


Increase your pedal ratio to 4:1 or even 5:1 ---- if you can keep all things aligned properly....

Add an electric vacuum pump .....


Or junk that set up and run a good manual master cylinder and get your pedal ratio to 6 or 7:1 <this would be my choice>

Or go to a "hydraboost" boost system....



What option would give me the best results? Manuel Brakes or an Electic Vacuum Pump setup with power brakes.

For manual brakes, i will need a special MC?

[GregWeld]

What option would give me the best results? Manuel Brakes or an Electic Vacuum Pump setup with power brakes.

For manual brakes, i will need a special MC?



Two things for the manual brakes --- a Wilwood 1" master cylinder....



Here's a page with several choices --

http://shop.ronsuttonracetechnology.com/shopping/productDetails.aspx?i=752196&c=7250


AND changing your brake pedal ratio to 6:1



You may already have another hole in the brake pedal -- or you might have to buy a master brake pedal with the correct ratio.... I don't know without being there and looking at it - but either way -- these cars came with manual brakes so parts should be available for a conversion.

[Musclerodz]

With that booster and those brakes, you need 1 1/8 master. Install a set of reduced angle booster brakes and redrill the brake pedal just under the manual hole on the pedal. Another thing is you need to bed the pads. They are probably glazed at this point making the feel worse. Its not ideal vacuum, but the dual diaphragm booster should be able to keep up. If not you could be real slick and use a RS vac cannister as a reservoir.

[GregWeld]

With that booster and those brakes, you need 1 1/8 master. Install a set of reduced angle booster brakes and redrill the brake pedal just under the manual hole on the pedal. Another thing is you need to bed the pads. They are probably glazed at this point making the feel worse. Its not ideal vacuum, but the dual diaphragm booster should be able to keep up. If not you could be real slick and use a RS vac cannister as a reservoir.



That master he's running now didn't have a real healthy look to it as it is....


I ran a reservoir vac cannister on one of my cars --- it was only good for about 1 1/2 brake accusations..... which - in traffic these days - wasn't worth the effort to mount and plumb. I also ran an electric pump -- even with a thumping 427" small block -- I couldn't stand the constant noise it produced.

TOTALLY AGREE on the glazed pads and rotors.

[67_camaroRS]

upon research I found out that the MC im running right now is from a 68 to 75 Corvette. the MC bore size is 1.125 in. ill check the brake pads and rotors this weekend. Im going to go with manual brakes. But my dad is trying to convince me to add a vacuum pump from 2013 camaro he believes that it shouldn't be noisy. Thanks