[ChevyCam]

Well after searching through a bunch of posts regarding this subject, I just have to post my own problem.

Here's the deal: I switched my front drums to discs using a Stainless Steel kit which went together fairly painlessly. Now that I am driving the car around, the problem I am having is that when I try to step hard on the brakes to stop the car quickly, it just doesn't do it. The pedal doesn't go to the floor, it just kind of hits like a point where it won't go down any farther but it doesn't grab the brakes any harder making the car not stop any quicker if I step harder. That's the best I can explain it...

I have bled the brakes many times, and am getting good fluid flow from all the bleeders. Next I checked the rod length to the master booster and it is the correct length according to david pozzi's website. So now I really don't know why I would be getting this weird pedal feel....

I don't have a porportioning valve installed in between the distribution block and rear drums. I'm not sure if that has anything to do with it, I doubt it..

I just don't have any ideas.. so help me out!!

Thanks,

Mike

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94 Z28 Convertible
68 Camaro SS Clone

[Judd]

I can't give you any technical answer but, if GM put a Pro Valve on the car I would have to assume that they did it for a good reason. I too used new stainless lines in my drum to disc conversion. I also put a rebuilt/stock ProValve and I think that the pedal feels great. Many people have voiced their opinions that the stock feel is no good but, I have to disagree. Perhaps Mr. Pozzi can shed some light on this matter.

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1969, X-44, Export Model, Hugger Orange, Std. Int., BC Rear(soon to be a BT 12 bolt), PDB, GMPP 350HO, M22 Supercase, SSM Lift Bars, AirGap, Holley 750, FlowMaster American Thunder Exhaust, FlowTech Headers

[Silver69Camaro]

My Camaro pretty much feels the same way. I've got a manual brake setup ('67 Camaro MC) and the rest of the components are from a '71 Monte.

I can push that pedal pretty hard and not lock up the brakes, maybe that's a good thing. I'm pretty sure it's bled correctly, although my brake pads are a bit old. Maybe 'cause I have no power assist?

My last Camaro had power brakes, and I could lock the front wheels fairly easily.

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1969 Base Camaro
Vortec 355, Perf. RPM, Demon Carb., TH-400
All sheetmetal is NOS GM
See my webpage at: http://www.geocities.com/compuboy007/

[davidpozzi]

Did you put on a 1" bore disc master cyl? I'm assuming you have manual brakes.

Manual stock type discs using a 1" bore are reported to be very hard to lock a wheel on.
A 15/16" bore master cyl may be the answer, but pedal travel will increase and has to be considered.
The 88 S-10 master cyl is a good way to go if you can overcome the pushrod problems outlined on my page.
There are a lot of different brake pads out there that may help if you can find some with a higher coefficient of friction.
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer

[ChevyCam]

No, actually they are power brakes... sorry I forgot to say that

Thanks,

Mike

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94 Z28 Convertible
68 Camaro SS Clone

[Garydmx]

I have a similar situation. I have front disk/rear drum. I have Stock size Brutestop rotors drilled and slotted in front and normal drums in back. The disk pads and shoes are Brutestop semi-metallic. I bought Master Power Brakes dual diaphram booster, master cylinder and electric vacuum pump with new proportioning valve. Now, here's what happens... when first driving it is similar to what you say. I cannot get it to lockup. Once disks have warmed up it starts to get real tacky and requires very little pressure. If I panic stop it just barely locks them up. It acts like anti-lock in a way. But I too am thinking that there should be more to it. I have bled everything with the old pump and hold. I even used a Mitey Mite vacuum pump. I'm really leaning towards the fact that it is the composition of the pads and shoes that makes this occur. Any ideas?

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1969 Camaro Z/28 clone 406 SB/450hp TH400, 12 bolt w/3.73 gears, Extreme Comp Cam CS EX284H .507/.510 lift

[davidpozzi]

Check your engine vaccum, you need around 17" minimum to operate the booster.

The "standard" Performance Friction pads are better to use on the street than their HD pads. the HD pads don't stop easily when cold.

Make sure the rear brakes are doing their part. If they don't work well, added load is put on the front wheels.

You may be able to drop the master cyl bore size to gain pressure. 1" should work, 15/16" may work too but the MC piston may come pretty close to bottoming.

70's Corvettes with manual brakes use a 1" bore.
I would think with a vaccum pump, there should be enough vaccum to lock a wheel. If anything the early discs had too much assist stock.
David


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Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer

[This message has been edited by davidpozzi (edited 10-08-2002).]

[ChevyCam]

david,

My engine is only producing 12" of vacuum around idle, but I figured that you would just have to step harder on the pedal to make the car stop quicker, also I'm still feeling this when the engine has been revved up and then slam on the breaks, so wouldn't the booster already get enough vacuum from that? Or maybe I need a electric vacuum pump?

The problem really doesn't seem to get much better when the brakes are hot either..

I had just rebuilt the rear brakes with new pads and springs etc. They are adjusted fine.

I just don't know..

Mike

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94 Z28 Convertible
68 Camaro SS Clone

[Torker]

A couple of things...

First, Assuming you have the correct master cylinder, and there is no air in the line:
Did your SSbrakes kit come with zinc washed rotors? and are you using SSbrakes pads?

If so the zinc wash, when it gets hot and starts to melt off the rotor surface, will prevent the pad from working properly. CarlC has been having a similar problem with his SSbrake stuff - it just won't lock up. Even the parking brake won't hold his car on a LEVEL surface.
To fix this, pull the rotors off and hit them with some emery cloth and make sure ALL the zinc coating is off the pad surface. - I would recommend a different set of pads as well. I have had a lot of success with Hawk HPS carbon pads.

Second, 12" of vacuum is on the low side. To work properly the vacuum booster really likes to see 14-15". I fought this problem for years with vacuum cans etc. before switching to a hydro-boost. My car with its hydro boost will stop on a dime. You may want to consider the swap, especially if you are planning any future engine mods that will reduce your idle vacuum.
I hope you get the problem solved.

[ChevyCam]

Torker,

I'm not sure if the rotors are zinc washed.. how can I tell?
And yes I am using the SS brakes pads that came with the kit.

Is it worth it for me to add an electric vacuum pump to add some more vacuum for the booster?

Thanks,

Mike

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94 Z28 Convertible
68 Camaro SS Clone

[This message has been edited by ChevyCam (edited 10-09-2002).]

[CarlC]

A couple of questions...

Which power booster do you have? If it is the smaller booster that SSBC offers it does not offer as much assist as the stock large-diameter booster. SSBC wants 17+ inHG for these units but my engine only makes 13 inHg at idle. I do not have the room to run a pump so it's not an option.

What caliper and rotor are you using? Stock, PBR, etc. With a stock booster, master cylinder, rotor, and caliper I could lock the brakes with a standard street semi-metalic pad. When the vacuum was low (engine cold) the pedal sometimes got hard, but a blip of the throttle was enough to cure it. David is right, the stock systems have a lot of assist, but when you combine smaller diameter boosters, bigger master cylinders, smaller piston calipers, zinc washed rotors, and funky pads all bets are off.

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The Red Beast http://www.geocities.com/casanoc

[This message has been edited by CarlC (edited 10-09-2002).]

[ChevyCam]

CarlC,

Thanks for the reply, I do have the smaller diameter booster that SSBC offers. I got all this stuff in a kit. It has the stock master cylinder and the stock calipers with the SSBC brake pads and rotors. Again, I don't know if they are zinc washed or not, and don't know how to tell..

So should I change the pads? would that help?

Thanks,

Mike

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94 Z28 Convertible
68 Camaro SS Clone

[CarlC]

If the rotors are zinc washed they will be a silver color all over. If they are a bare cast iron and have any signs of rust then they are bare.

A higher friction pad may help. The smaller booster is likely the deal killer. If you have a large GM booster you might want to give it a try. You can also try, as David mentions aboove, a 1" or 15/16" master cylinder. That would help.

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The Red Beast http://www.geocities.com/casanoc

[Go69]

Torker,
In regards to the Hydro-Boost, is this the system that uses pressure from the power steering pump to add assist to braking?

If so, can you help me out with some sourcing information?

Specifically, I would like to know where I can find the parts/pieces to make this kind of changeover.

Please advise!

Thank you very much!


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1969 Camaro SS 350-383ci., T-56, 12 bolt, Eaton posi, 3.31 gears, 4 wheel disc, Deluxe black houndstooth interior, rear window defogger, tilt steering, console w/AutoMeter gauge package, center mntd. clock, Tach.

[CarlC]

Try American Brake and Steering in Orange County, CA.
http://www.abspowerbrake.com

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The Red Beast http://www.geocities.com/casanoc