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Discussion Starter #1
I have a brake problem that I just can't seem to figure out. My system is all new. SSBC front super duty kit and their standard rear disc kit. All new lines and I'm just using the stock distribution block and an adjustable prop. valve in the rear line. I believe I have them bled good. I have a hard pedal but I can only get 500 psi to each caliper(need 1000-1200). I checked the booster, it is not leaking. I have the rod in the bottom hole on the pedal. The only thing that doesn't seem right is that I pulled the vacuum line off at the check valve and checked the vacuum. I only get 14-15 inches. SSBC says I need at least 18 to operate the brakes. Shouldn't the booster build up the vacuum enough to operate them? My motor is a 2002 LS1 with the GM hotcam. There are plenty of guys running this cam and bigger ones with no brake problems. I don't know if it is my motor/vacuum causing the brakes not to work or something with the brakes themselves. Any help/suggestions you have would be greatly appreciated. Thanks, John
 

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Sounds like the wrong master cylinder size, brake tube sizing or it could be the vaccume but I wouldnt point a definitive finger at that just yet. You should still be able to create enough pressure without the booster......

Did your car originally come with four wheel drum? You might have to change the prop/metering valve because of this. Might want to re-confirm the position of where the rod needs to be with the system you have installed.
 

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Discussion Starter #3
Yes it was originally a 4 wheel drum car. But I'm not using any metering valve. The rod was in the upper hole for manual and I put it in the lower hole for power.
 

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John, I know this isnt helping but how did you hook up your rear E brakes? I have a 69 and cant seem to get the friggen cables figured out neither line holder works.
 

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Discussion Starter #5
Stenn5, With mine being an automatic, I did not even bother hooking them up.
 

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John,
I'm running a automatic too, but would at least try to make the damn things work. Did you try to hook em up? I know when I called SSBC they said there are hundreds sold with no problem,
Thanks,
Mike
 

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Discussion Starter #8
Master cylinder bore is 1 1/8".

Stenn5, No I have not even tried.
 

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Discussion Starter #10
I thought you would only want one that small for manual brakes. I would think bigger would be better for power brakes. Am I wrong about this?
 

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Originally posted by john68conv:
I thought you would only want one that small for manual brakes. I would think bigger would be better for power brakes. Am I wrong about this?
It all depends on the caliper bore size. With small PBR style calipers up front I would run a 15/16" or 1" MC with some sort of power assist (hydroboost, vacuum boost, powermaster, vacuum pump etc.).

I don't know what size calipers the SSBC kit comes with but it sounds like you aren't being able to generate enough line pressure to get the system to work.

Joe
 

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The stock MC for the large single caliper on most power assisted GM cars is 1 1/8". Since the caliper piston is so large a lower line pressure is needed to obtain the necessary clamping force.

However, the caliper piston size in the PBR and T-bird calipers that SSBC provides is much smaller than the stock single-piston caliper. Hence, more line pressure is needed to obtain the same clamping force.

As an example, Ford uses a 1" MC on hydraboosted Mustangs. The front caliper is the same as yours, the rear is similar in piston size.

The hydraboost offers WAY more assist than a vacuum booster, especially at low vacuum and/or smaller booster diameter.

Now, if Ford deemed it necessary to use a 1" MC with a hydraboost, then lets assume that 1" is the correct MC size. Let's choose 1000 psi line presure as an example. For the 1" MC it will require 785# pushing on the piston. For the 1 1/8" it will require 994#. That means you will need to apply 27% more leg strength to the 1 1/8" MC just to be equal.

Now throw in the hydraboost factor. My stock, large diameter booster, with a 1" MC, engine revved up to make 18+ inHg only made 900-1000 psi line pressure using a gorrilla leg. The Hydraboost makes 1400 psi, using the Ford 1" MC (I believe) using less leg.

I believe that chicane67 uses a large MC in his Baer equiped 13"/12" package, but in a manual format with a grippy pad. Hopefully he will chime in here.

The best way to handle the rear parking brake cable for the T-bird caliper is to have custom cables made. On Torker's website he has the company listed that made our cables. I think it's Control Concepts in Santa Fe Springs, CA. I'll try to confirm the name and phone number.
 

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Discussion Starter #14
Thanks for the help guys. Does anyone know what power master clyinder with a 15/16 bore would work for me? I'm really thinking about just going manual now with a 1" or 15/16". But I would not be opposed to trying a 15/16" power clyinder either. By the way, the calipers are PBR 2 piston on the front. Thanks, John
 

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Originally posted by john68conv:
Does anyone know what power master clyinder with a 15/16 bore would work for me? I'm really thinking about just going manual now with a 1" or 15/16". But I would not be opposed to trying a 15/16" power clyinder either. By the way, the calipers are PBR 2 piston on the front. Thanks, John
John,
You are going to hate the PBRs in a manual mode, especially in a panic situation. The small piston area of the PBR's is not able to generate enough line pressure at the rotor for sufficient clamping force when running a manual MC.

Does your power booster have a long or short pushrod? For a long pushrod use either a 1" 'Vette MC or a '77 Malibu six cylinder 15/16" MC. If it's a short pushrod you'll need to do some machine work on the O.D. to fit (for an early Moraine booster) the famous S10 quick take-up MC. That's what I used on my Chevelle's C5 PBR 13" brake conversion (see sig for pictures of the swap).

Anyone else have some MC ideas to try?

Joe
 

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ALL I can say is thats MP brakes for ya...They have been having several probs with rear kits!! I get a lot of calls from people that can't get answers from them! I don't sell their product so I don't know what components they use. We use the 68-72 corvette MC with all of our power kits! They work great but we also sell a 4 wheel disc brake kits and don not reccomend an adjustable valve unless you are using junkyard rear kits where the front and rears aren't matched! Also, does your rear kit have the Ebrake in the caliper or a drum brake inside the rotor?

Matt
 

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Discussion Starter #17
Matt, The brakes I'm using are from SSBC. Maybe the same as MP, I don't know. The rears are Thunderbird calipers. What size is that 68-72 power master?

Joe, Is that Malibu master for power or manual?
 

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Originally posted by john68conv:
What size is that 68-72 power master?

The power MC should be 1 1/8" bore.

Originally posted by john68conv:
Joe, Is that Malibu master for power or manual?
Manual brakes on a '77 Chevy Malibu with a 4.1L inline six. I'll have to dig up the part number.

Here we go. It can be found through the Autoline brand, part # 1639 or ACDelco part # 18M500.

Be sure and check the MC bore (it should be 15/16") before you leave the parts counter, as I've heard of guys getting the 1 1/8" bore MC from the idiot counter guy ordering the power MC instead of the manual MC!.

Man, I can't believe SSBC would sell you a kit that doesn't even include instructions for the simple stuff like this! Makes me :mad: & also makes me want to go into the business and leave them in the dust!

**Edit**

I forgot to also mention that this MC has the reservoirs reversed. Meaning, the traditional rear port is usually for the rear brakes and the front is for the front brakes.

Not so with this MC, the rear reservoir is for the front brakes and the front reservoir is for the rear brakes. Nothing major and you probably would have noticed this when you got the MC.


Joe

[ 07-16-2003, 11:17 PM: Message edited by: 72SSAbody ]
 

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Discussion Starter #19
Thanks Joe, If I go to manual that is what I will try. Does anyone know of a power master with a 15/16 or a 1" bore?
 
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