Do I have the right master cylinder ?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Bernie** · 02-25-2006, 05:41 PM

I've been having trouble bleeding my brakes and centering the combination valve and got to wondering if I made a big mistake at the start. I have a K20 with the axles off a 1978 k20 so I have discs at the front and a 14 bolt rear with big drums. I bought a combination valve and new master cylinder. I mounted the valve up beside the MC, the frame was bare when I got it so I don't know much about where the brake lines should go. I thought that the bigger chamber of the master cylinder works the disc brakes, the bigger chamber on mine is at the back near the booster and I connected the brake line from the back of the MC , under the bigger chamber, to the port on the valve nearest the take off port for the front brakes. I looked at another master cylinder and saw that the bigger chamber is on the front. Were there two sorts of master cylinders made with the chambers swapped over ? Was I right in thinking that the front intake to the combination valve is next to the exit port for the front brakes ? I know which is the front exit from the Chilton manual. Sorry so long, any help would be appreciated.
Bernie

**truckdude239** · 02-26-2006, 01:58 AM

on my 71 c-10 the mc the chambers are the same size and i have front disc but mine are hooked up to the front chamber on mine feeds the front disc might be the back chambver is bigger for the back brakes because its a long disatnce to travel so it takes more fuild

davidh · 02-26-2006, 01:23 PM

Hmm. This is a good thread. I'm supposed to be getting a 69 3/4 4x4 with no motor soon. I want to build it up, put later model 3/4 axles with disc on it too. What about using the set up from a 78 truck? Maybe look at 70's 4x4 to look at it.

**Bernie** · 02-26-2006, 02:01 PM

I bought the frame and axles from a member, Blazerman. The axles, off a 78 3/4 ton were already installed. It seems a nice set up. Discs on the front and huge drums on the 14 bolt axle. I got a new cab and bed and tranfered the rest from my rusted out C10. The only downside is that I don't know how things are supposed to be, hence my question.

**john** · 02-26-2006, 02:46 PM

On C 10's the the front of m/s goes to front brakes. On C 20's the front goes to the rear brakes. I would assume that K models are the same, but you know what they say about assumptions. John

**VetteVet** · 02-26-2006, 04:47 PM

You guys might like to read this article.

http://www.hotrodheaven.com/tech/bra...kes1_index.htm

cableguy0 · 02-26-2006, 05:08 PM

the big line is for the drums the smaller line is for the disks. the disks require higher pressure and not at much volume ie smaller line to front. the drums use more fluid but lower pressure

02-25-2006, 05:41 PM	#1
Bernie Senior Member Join Date: Jan 2001 Location: Northern Illinois Posts: 516	Do I have the right master cylinder ?? I've been having trouble bleeding my brakes and centering the combination valve and got to wondering if I made a big mistake at the start. I have a K20 with the axles off a 1978 k20 so I have discs at the front and a 14 bolt rear with big drums. I bought a combination valve and new master cylinder. I mounted the valve up beside the MC, the frame was bare when I got it so I don't know much about where the brake lines should go. I thought that the bigger chamber of the master cylinder works the disc brakes, the bigger chamber on mine is at the back near the booster and I connected the brake line from the back of the MC , under the bigger chamber, to the port on the valve nearest the take off port for the front brakes. I looked at another master cylinder and saw that the bigger chamber is on the front. Were there two sorts of master cylinders made with the chambers swapped over ? Was I right in thinking that the front intake to the combination valve is next to the exit port for the front brakes ? I know which is the front exit from the Chilton manual. Sorry so long, any help would be appreciated. Bernie __________________ Bernie

02-26-2006, 01:58 AM	#2
truckdude239 Senior Member Join Date: Sep 2005 Location: Lewisville, Nc Posts: 10,237	Re: Do I have the right master cylinder ?? on my 71 c-10 the mc the chambers are the same size and i have front disc but mine are hooked up to the front chamber on mine feeds the front disc might be the back chambver is bigger for the back brakes because its a long disatnce to travel so it takes more fuild __________________ David fuller Ase Certified Mechanic Click here to help support our board!! 1971 Chevy c-10 under going a 4.8l LSx swap Build Thread http://67-72chevytrucks.com/vboard/s...d.php?t=421305 2007 Honda Accord my daily 145kmiles 2002 Honda Accord 4 door With 330k(sisters car) 2005 toyota Avalon 228k( brothers car) 2002 Sububran 5.3 245k 2000 Tahoe 5.3l 378 General manager for Marco's Carwash & lube

02-26-2006, 01:23 PM	#3
davidh Senior Member Join Date: Feb 2004 Location: Ponca city now kingfisher Oklahoma Posts: 1,220	Re: Do I have the right master cylinder ?? Hmm. This is a good thread. I'm supposed to be getting a 69 3/4 4x4 with no motor soon. I want to build it up, put later model 3/4 axles with disc on it too. What about using the set up from a 78 truck? Maybe look at 70's 4x4 to look at it.

02-26-2006, 02:01 PM	#4
Bernie Senior Member Join Date: Jan 2001 Location: Northern Illinois Posts: 516	Re: Do I have the right master cylinder ?? I bought the frame and axles from a member, Blazerman. The axles, off a 78 3/4 ton were already installed. It seems a nice set up. Discs on the front and huge drums on the 14 bolt axle. I got a new cab and bed and tranfered the rest from my rusted out C10. The only downside is that I don't know how things are supposed to be, hence my question. __________________ Bernie

02-26-2006, 02:46 PM	#5
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Re: Do I have the right master cylinder ?? On C 10's the the front of m/s goes to front brakes. On C 20's the front goes to the rear brakes. I would assume that K models are the same, but you know what they say about assumptions. John __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

02-26-2006, 04:47 PM	#6
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,718	Re: Do I have the right master cylinder ?? You guys might like to read this article. http://www.hotrodheaven.com/tech/bra...kes1_index.htm __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

02-26-2006, 05:08 PM	#7
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	Re: Do I have the right master cylinder ?? the big line is for the drums the smaller line is for the disks. the disks require higher pressure and not at much volume ie smaller line to front. the drums use more fluid but lower pressure __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

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