Prop valve question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Harold Shepard · 02-27-2005, 06:09 PM

I am currently changing over a 69 mdel truck to disk brakes. I had already bought new brake lines (great deal- $20 for the 6 metal lines in front) with the plans to use the praise dyno brake kit. A 71 parts truck landed in my lap and now I have switchd gears and am using the spindles etc for disks (too far gone to stop- new upper and lower ball joints, tie rods etc.) But now I have a problem and I'm sure some one has run into it. How are you modifing the prop valve from the 71-72 to work with the 69 brake line set-up? By the way this is a power brake truck. Any input is greatly appreciated.

Longhorn Man · 02-27-2005, 06:37 PM

You should use the disc/drum master cylinder in addition to the proportioning valve. The line pressure is way higher on a disc caliper and the full potential of the discs will not be realized onless you do it all right.

Harold Shepard · 02-27-2005, 08:28 PM

I was planning to use the 71-72 M/C (Bendix) but the stock lines are going to be a pain- I hate to bend them to crap as they are new. What do you suggest to connect the 69-70 stock steel lines to the 71-72 prop valve and M/C as the dist. valve and the prop valve are two different things and as such the steel line don't exactly match up and I don't want it to look jerry- rigged. Harold

cableguy0 · 02-27-2005, 08:37 PM

the best way would be to sell the lines you have and make new ones the disk brake lines for the front are of smaller diameter

02-27-2005, 06:09 PM	#1
Harold Shepard Registered User Join Date: May 2004 Location: Canton North Carolina Posts: 466	Prop valve question I am currently changing over a 69 mdel truck to disk brakes. I had already bought new brake lines (great deal- $20 for the 6 metal lines in front) with the plans to use the praise dyno brake kit. A 71 parts truck landed in my lap and now I have switchd gears and am using the spindles etc for disks (too far gone to stop- new upper and lower ball joints, tie rods etc.) But now I have a problem and I'm sure some one has run into it. How are you modifing the prop valve from the 71-72 to work with the 69 brake line set-up? By the way this is a power brake truck. Any input is greatly appreciated.

02-27-2005, 08:37 PM	#4
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	the best way would be to sell the lines you have and make new ones the disk brake lines for the front are of smaller diameter __________________ 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.

02-27-2005, 06:37 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	You should use the disc/drum master cylinder in addition to the proportioning valve. The line pressure is way higher on a disc caliper and the full potential of the discs will not be realized onless you do it all right.

02-27-2005, 08:28 PM	#3
Harold Shepard Registered User Join Date: May 2004 Location: Canton North Carolina Posts: 466	I was planning to use the 71-72 M/C (Bendix) but the stock lines are going to be a pain- I hate to bend them to crap as they are new. What do you suggest to connect the 69-70 stock steel lines to the 71-72 prop valve and M/C as the dist. valve and the prop valve are two different things and as such the steel line don't exactly match up and I don't want it to look jerry- rigged. Harold



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