Need brake system help

[Yukon Jack]

On my 1969 K20, when I put in the 454, I also put in the hydroboost system from the donor 1989 1 ton 2wd truck. My 69 K20 had a manual brake system, drums all around.

When I put in the hydroboost, for what ever reason I did away with the block that you see in the below pic shown on the old system so the hydroboost front brake line went directly to the factory splitter that than sends it to the left and right brakes. The rear line just goes straight to the rear brakes.

I'm installing a Dana 60 front axle from a 1984 Crew cab which will of course gain me front disk breaks (can't wait for that improvement!!!!) I'm presuming I will need to add an adjustable proportioning valve on the rear brake line.

I've read some people mention when they add disk brakes they have to add a 2 lb residual valve.

Here is the existing hydroboost installed in my 69 K20

In looking at pics of the hydroboost before I pulled it from the donor truck, I can't find any pics that show whether a proportioning valve was somewhere within the system.

Can anyone shed some light on my situation so I can figure out what changes I need to make to my existing system. I would add, when it's time to have brake work done on the existing rear Eaton axle, I will probably swap disk brakes instead of keeping the drum brakes as I've heard brake pads are a bit difficult to find for that axle.

I will note the all drum system was working fine with the hydroboost as I had it set up, but I am a little confused on why I didn't put the factory block shown in the above pic into the hydroboost system or maybe put in the donor trucks proportioning valve (assuming a 1989 1 ton 2wd would have had a proportioning valve). I do recognize that my existing system does not have a sensor that allows an idiot light to light up if the system were to fail or lose pressure.

 

[bigblock72]

You will need to add an adjustable proportioning valve similar to this:

http://www.summitracing.com/parts/WIL-260-8419/

The proportioning valve will simply splice into the rear brake line. It should reduce the pressure enough to keep the rear drums from locking up and still allow you turn the pressure up when you get your disc brakes mounted on the rear. Converting the rear brakes is cheaper and easier then trying to find shoes and drums for a HO52/72.


There isn't any need for a residual pressure valve because your master cylinder is mounted above the wheel cylinders/brake calipers. Simply add in the proportioning valve, adjust it properly and forget about it. Anything else is jsut needlessly complicating a simple operation.

The 89 truck would have had a combination valve mounted down on the frame.

 

[Yukon Jack]

Awesome - thanks for the info!

 

[tRustyK5]

I tend to agree, I never added a residual valve to my Jimmy. Hydroboost, 60/14 with rear discs. With the weight bias of my K5 it'd lock all 4 up at roughly the same time on 40's.

Rene