New master and now no power brakes

[BurnoutNova]

A 1 1/8" bore is not typically used for disc brakes. I don't think that was the problem. Maybe they gave you a drum/drum prop valve. I would start by checking the fluid pressure at the calipers. Should be between 800-1200 psi.

[lolife99]

Drum/drum set ups have a distribution block, not a proportioning valve.
The 71-72 M/C with a booster had a 1-1/8" bore.

[nds1968]

Originally Posted by lolife99

That's why I will only use aluminum M/C's from now on.
No painting that will eventually rust anyway.
I painted my '69 M/C with cast look caliper paint,... but now it's starting to look like crap.
(with almost no miles on the truck)

Do you know where to buy a stock looking aluminum M/C other than from PICKMUP? Thanks, Nate

[lolife99]

Originally Posted by nds1968

Do you know where to buy a stock looking aluminum M/C other than from PICKMUP? Thanks, Nate

http://www.speedwaymotors.com/Alumin...nder,8905.html

http://www.performanceonline.com/Dis...h-Performance/

http://ssbrakes.com/i-10092246-maste...-aluminum.html

[shawno72]

Well I replaced the master with the 1 1/8 bore master and the brake pedal is worse. The pedal stroke is better but overall it is a tad bit worse. I'm thinking that maybe the brake pads just need to seat in.

[shawno72]

What would the symptoms be if I had a disc/disc prop valve?
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[lolife99]

Are you sure you have all the air out?

How much "free play" in the pedal?
(should be 1/8"-1/4")

[shawno72]

Free play is about 1/4 or less. Nothing but clear fluid being bleed out. Really feels like maybe it needs a stronger booster? I don't know what to do.
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[shawno72]

Even though I bought my prop valve from CPP the only markings on it are "PM" One I had before had the correct part number PV2.
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[BurnoutNova]

Originally Posted by shawno72

What would the symptoms be if I had a disc/disc prop valve?
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The rear drums would want to lock up, as the self energizing drums require much less pressure.

A 71/72 prop valve should deliver more pressure to the front calipers than to the rear line. A drum/drum "metering block" is just going to deliver straight line pressure to all 4 wheels.

[BurnoutNova]

I would put that 1" bore master back on, and then check your actual pressure at the caliper. If it is 800-1200 psi you can assume the pads need to seat in, or maybe the rotor finish is really bad and the pads are glazed over.

[shawno72]

Originally Posted by BurnoutNova

The rear drums would want to lock up, as the self energizing drums require much less pressure.

A 71/72 prop valve should deliver more pressure to the front calipers than to the rear line. A drum/drum "metering block" is just going to deliver straight line pressure to all 4 wheels.

Originally Posted by BurnoutNova

I would put that 1" bore master back on, and then check your actual pressure at the caliper. If it is 800-1200 psi you can assume the pads need to seat in, or maybe the rotor finish is really bad and the pads are glazed over.

I have a brand new aluminum 1" bore MC and brand new aluminum disc/drum prop valve ordered. I'll post updates once installed. Thanks for all the help. It's funny cause the brakes are feeling a tiny bit better each day......or I'm just getting used to them

[cericd]

Hey Shawn, any updates on the brake issue?

[Ol Blue K20]

Originally Posted by cericd

Hey Shawn, any updates on the brake issue?

x2

[Longhorn 70]

Yeah Shawno.... What's the news. I ask because mine feel like they are getting worse each day! It now feels like my pedal is bottoming out the M/C in the bore.

Maybe I got a bad M/C

[shawno72]

Well guys I got an aluminum master that will go on Saturday, I re adjusted the rear brakes nice and tight and the pedal has been fine. I still think the new master with the 1" bore will be the cats meow. I'll update you guys on Saturday.

[nds1968]

Originally Posted by cericd

hey shawn, any updates on the brake issue?

x2

[shawno72]

Sorry guys been super busy at work so no new master installed yet. Ever since I re adjusted the rear brakes they hav been fine so I am a little hesitant to swap on the aluminum master for fear they may be worse
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[Longhorn 70]

He who dares wins!

[knomadd]

Hey Shawn, have you ever checked how much vacuum your truck is producing? Do a simple vacuum test and see if your in the 18"-22" range. If you're below 18" of vacuum, you won't have enough to operate them on a vacuum booster as well as you would expect. They will still work, but just like you're explaining.

When I had this problem with my GTO, I thought I had bled the system pretty well, but wound up paying a shop to pressure bleed my brakes and they were able to get more air out, which helped but still didn't get it to where my drums were. I found out that I didn't have enough vacuum to operate the typical vacuum booster so I switched to hydraulic.

Do a vacuum test so you can at least rule that out. I'm curious if your next swap will fix your problem. Good luck!