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#26 |
Registered User
Join Date: Jan 2014
Location: Wasilla Alaska
Posts: 537
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Re: brake question
my 63 C10 just has on line goin to everything from one master cly. at the tee going to the rear brakes they go to a smaller dia. line. The slave clys. are all the same dia. I think just usen a dual cly. master cly. and a real adjustable proportioning valve for the rear is probably the way to go on drum/drum. I'm pretty sure if the frts fail we only lose halve of the master cly.
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#27 |
Registered User
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,332
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Re: brake question
There are two functions (and more but let's keep it simple):
Distribution - one line in, two out, for example Proportioning - adjusting pressures between two circuits in a relative manner Combined they are (wait for it) a "combination valve". A proportioning valve, like a distribution block, can be purchased separately and is a different thing. So, not to be "that guy", but we might as well keep out terms straight. In the vast majority of cases, people mean "combination valve".
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1970 GMC Sierra Grande Custom Camper - Built, not Bought 1969 Pontiac 2+2 427/390 4-speed Coupe 1969 Pontiac 2+2 427/390 4-speed Convertible |
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#28 |
Senior Member
![]() Join Date: Oct 2014
Location: New Palestine In
Posts: 931
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Re: brake question
To answer frankslagoon's question, no you don't need a distribution block in a drum/drum system. Its only function is the warning light if front or rear fail.
The brake pedal will tell you, you'll lose some pedal pressure. |
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#29 |
Registered User
Join Date: Jan 2014
Location: Wasilla Alaska
Posts: 537
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Re: brake question
That's what I thought. ok good
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#30 |
Registered User
Join Date: Jan 2014
Location: Cowpens S.C.
Posts: 138
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Re: brake question
I wonder why my truck did not have a proportioning valve on it?? But with a few other things that I have saw that the PO did, it does not surprise me.
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#31 | |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,193
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Re: brake question
Quote:
Drum/Drum - single pot master cylinder: one line out of master into distribution block, three lines out (LF wheel, RF wheel, rear system). Drum/Drum - dual pot: front line out of master cylinder into "T" distribution (LF wheel, RF wheel); one line out of master cylinder to rear system. So a simple "T" block at the least, even if no switch is desired. K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ Last edited by Keith Seymore; 02-04-2016 at 08:49 AM. |
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#32 | |
Registered User
Join Date: May 2009
Location: Motor City
Posts: 9,193
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Re: brake question
Quote:
I would recommend that you install an adjustable prop valve in the rear system (like from Wilwood or a similar race car manufacturer). There are three elements that can be tuned in a production prop valve: meter, split point (psi) and slope (front vs rear). You can grab any prop valve and it will flow fluid but the odds of it being optimized for your set up, right out of the box, are pretty much nil. The adjustable valve would allow you to tune for your specific weight distribution, dynamic weight transfer and respective brake torques on the fly. K
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Chevrolet Flint Assembly 1979-1986 GM Full Size Truck Engineering 1986 - 2019 Intro from an Old Assembly Guy: http://67-72chevytrucks.com/vboard/s...d.php?t=342926 My Pontiac story: http://forums.maxperformanceinc.com/...d.php?t=560524 Chevelle intro: http://www.superchevy.com/features/s...hevy-chevelle/ Last edited by Keith Seymore; 02-04-2016 at 08:43 AM. |
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#33 |
Registered User
Join Date: Jan 2014
Location: Cowpens S.C.
Posts: 138
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Re: brake question
This is a factory disc/drum setup. Why would it only had the "block" that I showed in post #1? One line going to a tee on cross member for front & one line going to rear. No proportioning valve.
I will run a proportioning valve like is called for. |
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#34 |
Senior Member
![]() Join Date: Oct 2014
Location: New Palestine In
Posts: 931
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Re: brake question
Is it possible the PO just changed to discs up front without changing the M/C and distribution block?
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#35 |
Registered User
Join Date: Jan 2014
Location: Cowpens S.C.
Posts: 138
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Re: brake question
Very doubtful. Truck was bought for a 15 year old, torn apart by body shop to be painted, kid lost interest, parked it outside. When I bought it, I replaced spindles, rotors, calipers, whole 9 yards. Rotors were worn badly. I am 99% sure it has been on the road this way.
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#36 |
Senior Member
![]() Join Date: Oct 2014
Location: New Palestine In
Posts: 931
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Re: brake question
You say the rotors were worn badly, that makes me believe the M/C is drum/drum. The reason being on a drum/drum M/C there are residual check valves in the piston bores.These check valves allow some brake line pressure, about 10# to remain in the line when you release the brake pedal. That keeps the wheel cylinders from collapsing from the brake shoe return springs. The shoes stay closer to the drum so you don't have so much pedal travel. 10#'s of residual pressure on the front rotors will eat up pads and rotors in a hurry.
Hope this helps. |
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#37 |
Registered User
Join Date: Jan 2014
Location: Cowpens S.C.
Posts: 138
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Re: brake question
No way to ever know what went on before I acquired it. Main thing is get it right now.
Thanks for all the comments. |
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#38 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,436
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Re: brake question
>>10#'s of residual pressure on the front rotors will eat up pads and rotors in a hurry<<
Or, the rotors could just simply be worn out. Check to see if the MC has the residual valves by inserting a toothpick or paper clip into the hole. It will be in about 1/4" inside and sits inside the back of the brass seat. Pull the brass out, remove the valve and spring and reinstall the brass seat. Installing the brake line will fully seat the brass. You should only remove the one for the disc brake line if you find one. ![]()
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'67 GMC 2500, 292, 4spd, AC |
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